ST – Solar-Terrestrial Sciences

ST1.1 – Open Session on the Sun and Heliosphere

EGU2020-1654 | Displays | ST1.1

Electric-current Neutralization and Eruptive Activity of Solar Active Regions

Tibor Torok, Yang Liu, James E. Leake, Xudong Sun, and Viacheslav S. Titov

The physical conditions that determine the eruptive activity of solar active regions (ARs) are still not well understood. Various proxies for predicting eruptive activity have been suggested, with relatively limited success. Moreover, it is presently unclear under which conditions an eruption will remain confined to the low corona or produce a coronal mass ejection (CME).

Using vector magnetogram data from SDO/HMI, we investigate the association between electric-current neutralization and eruptive activity for a sample of ARs. We find that the vast majority of CME-producing ARs are characterized by a strongly non-neutralized total current, while the total current in ARs that do not produce CMEs is almost perfectly neutralized, even if those ARs produce strong (X-class) confined flares. This suggests that the degree of current neutralization can serve as a good proxy for assessing the ability of ARs to produce CMEs. 


How to cite: Torok, T., Liu, Y., Leake, J. E., Sun, X., and Titov, V. S.: Electric-current Neutralization and Eruptive Activity of Solar Active Regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1654,, 2020.

EGU2020-1777 | Displays | ST1.1

Observation-based modelling of magnetised CMEs in the inner heliosphere with EUHFORIA

Camilla Scolini, Jens Pomoell, Emmanuel Chané, Stefaan Poedts, Luciano Rodriguez, Emilia Kilpua, Manuela Temmer, Christine Verbeke, Karin Dissauer, Astrid Veronig, Erika Palmerio, and Mateja Dumbović

Coronal Mass Ejections (CMEs) are the primary source of strong space weather disturbances at Earth and other locations in the heliosphere. Understanding the physical processes involved in their formation at the Sun, propagation in the heliosphere, and impact on planetary bodies is therefore critical to improve current space weather predictions throughout the heliosphere. The capability of CMEs to drive strong space weather disturbances at Earth and other planetary and spacecraft locations primarily depends on their dynamic pressure, internal magnetic field strength, and magnetic field orientation at the impact location. In addition, phenomena such as the interaction with the solar wind and other solar transients along the way, or the pre-conditioning of interplanetary space due to the passage of previous CMEs, can significantly modify the properties of individual CMEs and alter their ultimate space weather impact. Investigating and modeling such phenomena via advanced physics-based heliospheric models is therefore crucial to improve the space weather prediction capabilities in relation to both single and complex CME events. 

In this talk, we present our progress in developing novel methods to model CMEs in the inner heliosphere using the EUHFORIA MHD model in combination with remote-sensing solar observations. We discuss the various observational techniques that can be used to constrain the initial CME parameters for EUHFORIA simulations. We present current efforts in developing more realistic magnetised CME models aimed at describing their internal magnetic structure in a more realistic fashion. We show how the combination of these two approaches allows the investigation of CME propagation and evolution throughout the heliosphere to a higher level of detail, and results in significantly improved predictions of CME impact at Earth and other locations in the heliosphere. Finally, we discuss current limitations and future improvements in the context of studying space weather events throughout the heliosphere.

How to cite: Scolini, C., Pomoell, J., Chané, E., Poedts, S., Rodriguez, L., Kilpua, E., Temmer, M., Verbeke, C., Dissauer, K., Veronig, A., Palmerio, E., and Dumbović, M.: Observation-based modelling of magnetised CMEs in the inner heliosphere with EUHFORIA, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1777,, 2020.

The Interstellar Boundary Explorer (IBEX) was launched in 2008 and has now returned observations over a full 11-year solar cycle (Solar Cycle 24). IBEX remotely images global ion distributions via charge exchange Energetic Neutral Atoms (ENAs) propagating inward from the heliosheath – the region between the termination shock and heliopause – and beyond. These observations have led to numerous discoveries about the outer heliosphere and its interaction with the surrounding interstellar medium. Heliospheric ENAs arise largely from two sources: the IBEX Ribbon, which is likely generated beyond the heliopause, in the very local interstellar medium, and the globally distributed flux (GDF), which is primarily produced in the heliosheath. In this talk we summarize some of the critical advances driven by IBEX observations. We also examine how the heliosphere and its interstellar interaction have evolved over the past solar cycle. For most of IBEX’s 11 years of observations, there was an overall reduction and then flattening of the ENA fluxes at all energies, consistent with a generally deflating, or shrinking, heliosphere. Over the past few years, IBEX has been observing the progressive response of the heliosphere to a large persistent increase in the solar wind output that passed 1 AU in the second half of 2014. This enhancement arrived at the outer heliosphere as indicated by an increase in the ENAs returning from the closest region of the inner heliosheath, south of the upwind direction, starting in the second half of 2016. Since then, the region of enhanced ENA emissions has expanded progressively outward from there, exposing increasingly further away regions of the heliosheath. IBEX observations over the past 11-years have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction.

How to cite: McComas, D.: A Solar Cycle of Observations with the Interstellar Boundary Explorer (IBEX), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5536,, 2020.

EGU2020-2069 | Displays | ST1.1 | Hannes Alfvén Medal Lecture

Magnetospheric Response to Solar Wind Forcing -ULF Wave - Particle interaction Perspective

Qiugang Zong

Sudden changes in solar wind forcing, e.g., those associated with interplanetary shocks and/or solar wind dynamic pressure pulses, can cause many fundamentally important phenomena in the Earth’s magnetosphere including electromagnetic wave generation, plasma heating and energetic particle acceleration. This presentation summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. 

Magnetosphere response to sudden changes in solar wind forcing, is not a “one-kick” scenario. It is found that after the impact of solar wind structures on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change associated with an interplanetary shock or a solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to different kinds of waves including poloidal mode ULF waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region usually contains two steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells. 

Generalized theory of drift and drift-bounce resonance with growing or decaying ULF waves  (globally distributed or localized)  has been developed to explain in situ spacecraft observations. The new wave-related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. The results showed in this presentation can be widely used in the interaction of the solar wind with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

How to cite: Zong, Q.: Magnetospheric Response to Solar Wind Forcing -ULF Wave - Particle interaction Perspective , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2069,, 2020.

EGU2020-17703 | Displays | ST1.1

The Solaris Solar Polar Mission

Donald M. Hassler, Jeff Newmark, Sarah Gibson, Louise Harra, Thierry Appourchaux, Frederic Auchere, David Berghmans, Robin Colaninno, Silvano Fineschi, Laurent Gizon, Sanjay Gosain, Todd Hoeksema, Christian Kintziger, John Linker, Pierre Rochus, Jesper Schou, Nicholeen Viall, Matt West, Tom Woods, and Jean-Pierre Wuelser and the Solaris Team

The solar poles are one of the last unexplored regions of the solar system. Although Ulysses flew over the poles in the 1990s, it did not have remote sensing instruments onboard to probe the Sun’s polar magnetic field or surface/sub-surface flows.

We will discuss Solaris, a proposed Solar Polar MIDEX mission to revolutionize our understanding of the Sun by addressing fundamental questions that can only be answered from a polar vantage point. Solaris uses a Jupiter gravity assist to escape the ecliptic plane and fly over both poles of the Sun to >75 deg. inclination, obtaining the first high-latitude, multi-month-long, continuous remote-sensing solar observations. Solaris will address key outstanding, breakthrough problems in solar physics and fill holes in our scientific understanding that will not be addressed by current missions.

With focused science and a simple, elegant mission design, Solaris will also provide enabling observations for space weather research (e.g. polar view of CMEs), and stimulate future research through new unanticipated discoveries.

How to cite: Hassler, D. M., Newmark, J., Gibson, S., Harra, L., Appourchaux, T., Auchere, F., Berghmans, D., Colaninno, R., Fineschi, S., Gizon, L., Gosain, S., Hoeksema, T., Kintziger, C., Linker, J., Rochus, P., Schou, J., Viall, N., West, M., Woods, T., and Wuelser, J.-P. and the Solaris Team: The Solaris Solar Polar Mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17703,, 2020.

EGU2020-22 | Displays | ST1.1

On the magnetic characteristics of magnetic holes in the solar wind between Mercury and Earth

Martin Volwerk, Charlotte Goetz, Ferdinand Plaschke, Tomas Karlsson, and Daniel Heyner

The occurrence rate of linear and pseudo magnetic holes has been determined during MESSENGER’s cruise phase starting from Earth (2005) and arriving at Mercury (2011). It is shown that the occurrence rate of linear magnetic holes, defined as a maximum of 10â—¦ rotation of the magnetic field over the hole, slowly decreases from Mercury to Earth. The pseudo magnetic holes, defined as a rotation between 10â—¦ and 45â—¦ over the hole, have mostly a constant occurrence rate, with a slight increas in front of the Earth and a decrease around the Earth. The width and depth of these structures seem to strongly differ depending on whether they are inside
or outside of Venus’s orbit.

How to cite: Volwerk, M., Goetz, C., Plaschke, F., Karlsson, T., and Heyner, D.: On the magnetic characteristics of magnetic holes in the solar wind between Mercury and Earth, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22,, 2020.

EGU2020-5379 | Displays | ST1.1

The nature and origin of moving solar radio bursts associated with coronal mass ejections

Diana Morosan, Emilia Kilpua, Erika Palmerio, Benjamin Lynch, Jens Pomoell, Rami Vainio, Minna Palmroth, and Juska Räsänen

Flares and coronal mass ejections (CMEs) from the Sun are the most powerful and spectacular explosions in the solar system, capable of releasing vast amounts of magnetic energy over relatively short periods of time. These phenomena are often associated with particle acceleration processes that are often observed directly by spacecraft here at Earth. At the Sun, there are no direct methods of measuring these particles, which is necessary to predict their origin and propagation direction through the heliosphere. However, accelerated particles, in particular fast electrons, can generate emission at radio wavelengths through various mechanisms. Here, we exploit radio observations of Type II and Type IV radio bursts that accompany CME eruptions, in particular those radio bursts that show movement with the CME expansion in the low solar corona. Using multi-wavelength analysis, reconstruction of the radio emission and CME in three dimensions, we aim to determine the sources and locations of electron acceleration responsible for the Type II and Type IV emission in relation to the CME location and propagation. Such studies are important to understand CMEs and the sources of electron acceleration to ultimately improve the lead time to these impacts here at Earth.

How to cite: Morosan, D., Kilpua, E., Palmerio, E., Lynch, B., Pomoell, J., Vainio, R., Palmroth, M., and Räsänen, J.: The nature and origin of moving solar radio bursts associated with coronal mass ejections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5379,, 2020.

One of the mysteries of solar energetic particle (SEP) events is the compositional variability in those events that are clearly shock-related and may be called gradual events.  In particular, the reason for the enhancement of Fe with respect to O or C at high energies has been debated over the past two decades, and yet it is still unsettled.  One hypothesis relates the compositional variability with whether the CME-driven shock is quasi-parallel or quad-perpendicular near the Sun, but this may not be easily tested using remote-sensing data alone. In recent years, however, CME-driven shock waves have been modelled by fitting shock-like features in EUV and white-light images with relatively simple shapes, and in combination with magnetic field models, ir is possible to compute shock parameters at the shock surface. In this presentation, we simulate a few CMEs whose associated SEP events show widely different Fe/O, using the Alfven wave Solar Model (AWSoM) that is part of the Space Weather Modeling Framework (SWMF). We constrain the input parameters of the simulations so that the observed pre-eruption corona, eruption and CME are well-reproduced. The shock surface, across which the shock parameters are highly non-uniform, is carefully traced, and the time-dependent connectivity of the shock surface with the observer at multiple spacecraft is compared with the SEP properties including composition. We discuss how much about the compositional variability of SEP events can be learned with this technique.

How to cite: Nitta, N., Jin, M., and Cohen, C.: Understanding the Origin of Variable Compositions of Gradual Solar Energetic Particle Events by Combining Observations and Numerical Simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21333,, 2020.

EGU2020-18133 | Displays | ST1.1

Comparing different types of solar flares with radio bursts detected by SMOS

Manuel Flores Soriano and Consuelo Cid

SMOS is an Earth observing satellite that is been adapted to provide full polarization observations of the Sun at 1.4 GHz 24 hours a day. Its solar radio observations from the last decade will be released to the community by the middle of this year. In this presentation we show the capabilities of SMOS as a solar radio observatory and compare some of the most relevant radio bursts with data from GOES, LASCO, SDO and RSTN. We show how SMOS responds to different kinds of solar flares depending on their x-ray flux, and the kind of mass ejection or solar dimming that they have produced, if any. In addition to this we also show the potential of SMOS as a space weather tool to monitor GNSS satellites signal fades and to provide an early warning of Earth-directed coronal mass ejections.

How to cite: Flores Soriano, M. and Cid, C.: Comparing different types of solar flares with radio bursts detected by SMOS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18133,, 2020.

EGU2020-18173 | Displays | ST1.1

Imaging the Solar Corona during the 2015 March 20 Eclipse using LOFAR

Aoife Maria Ryan, Peter T. Gallagher, Eoin P. Carley, Diana E. Morosan, Michiel A. Brentjens, Pietro Zucca, Richard Fallows, Christian Vocks, Gottfried Mann, Frank Breitling, Jasmina Magdalenic, Alain Kerdraon, and Hamish Reid

The solar corona is a highly-structured plasma which reaches temperatures of more than ~2MK. At low radio frequencies (≤ 400 MHz), scattering and refraction of electromagnetic waves are thought to broaden sources to several arcminutes. However, exactly how source size relates to scattering due to turbulence is still subject to investigation. This is mainly due to the lack of high spatial resolution observations of the solar corona at low frequencies. Here, we use the LOw Frequency ARray (LOFAR) to observe the solar corona at 120-180 MHz using baselines of up to ~3.5 km (~1--2’) during a partial solar eclipse of 2015 March 20. We use a lunar de-occultation technique to achieve higher spatial resolution than that attainable via traditional interferometric imaging. This provides a means of studying source sizes in the corona that are smaller than the angular width of the interferometric point spread function. 

How to cite: Ryan, A. M., Gallagher, P. T., Carley, E. P., Morosan, D. E., Brentjens, M. A., Zucca, P., Fallows, R., Vocks, C., Mann, G., Breitling, F., Magdalenic, J., Kerdraon, A., and Reid, H.: Imaging the Solar Corona during the 2015 March 20 Eclipse using LOFAR, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18173,, 2020.

EGU2020-21334 | Displays | ST1.1

Interplanetary shocks as a source of sustained gamma-ray emission from the Sun

Nat Gopalswamy and Pertti Mäkelä

It has recently been shown that the sustained gamma-ray emission (SGRE) from the Sun that lasts for hours beyond the impulsive phase of the associated flare is closely related to radio emission from interplanetary shocks (Gopalswamy et al. 2019, JPhCS, 1332, 012004, 2019). This relationship supports the idea that >300 MeV protons accelerated by CME-driven shocks propagate toward the Sun, collide with chromospheric protons and produce neutral pions that promptly decay into >80 MeV gamma-rays. There have been two challenges to this idea. (i) Since the location of the shock can be halfway between the Sun and Earth at the SGRE end time, it has been suggested that magnetic mirroring will not allow the high energy protons to precipitate. (ii) Lack of correlation between the number protons involved in the production of >100 MeV gamma-rays (Ng) and the number of protons (Nsep) in the associated solar energetic particle (SEP) event has been reported. In this paper, we show that the mirror ratio problem is no different from that in flare loops where electrons and protons precipitate to produce impulsive phase emissions. We also suggest that the lack of Ng – Nsep correlation is due to two reasons: (1) Nsep is underestimated in the case of eruptions happening at large ecliptic latitudes because the high-energy protons accelerated near the nose do not reach the observer. (2) In the case of limb events, the Ng is underestimated because gamma-rays from some part of the extended gamma-ray source do not reach the observer.

How to cite: Gopalswamy, N. and Mäkelä, P.: Interplanetary shocks as a source of sustained gamma-ray emission from the Sun, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21334,, 2020.

EGU2020-3711 | Displays | ST1.1

Effects of local particle acceleration in the solar wind

Olga Khabarova, Valentina Zharkova, Qian Xia, and Olga Malandraki

Recent observational and theoretical studies have shown that there is an unaccounted population of electrons and protons accelerated locally to suprathermal energies at reconnecting current sheets (RCSs) and 3-D dynamical plasmoids or 2-D magnetic islands (MIs) in the solar wind. The findings can be summarized as following: (i) RCSs are often subject to instabilities breaking those into 3D small-scale plasmoids/blobs or 2D magnetic islands (MIs) with multiple X- and O-nullpoints; (ii) RCSs and dynamical MIs can accelerate particles up to the MeV/nuc energies; (iii) accelerated particles may form clouds expanding far from a reconnecting region; and (iv) bi-directional(or counterstreaming) strahls observed in pitch-angle distributions (PADs) of suprathermal electrons may simply represent a signature of magnetic reconnection occurring at closed IMF structures (e.g., MIs), not necessarily connected to the Sun (Zharkova & Khabarova, 2012, 2015; Zank et al. 2014, 2015; Khabarova et al. 2015, 2016, 2017; 2018; le Roux 2016, 2017, 2018, 2019; Khabarova & Zank, 2017; Adhikari et al. 2019; Xia & Zharkova, 2018, 2020; Malandraki et al. 2019; Mingalev et al. 2019). We will briefly present an overview of the effects of local ion acceleration as observed at different heliocentric distances and focus on the impact of the locally-borne population of suprathermal electrons on typical patterns of PADs. 

Suprathermal electrons with energies of ~70eV and above are observed at 1 AU as dispersionless halo and magnetic field-aligned beams of strahls. For a long time, it has been thought that both populations originate only from the solar corona. This view has consequently impacted interpretation of typical patterns of suprathermal electron PADs observed in the solar wind. We present multi-spacecraft observations of counterstreaming strahls and dropouts in PADs within a previously reported region filled with plasmoids and RCSs, comparing observed PAD features with those predicted by PIC simulations extended to heliospheric conditions. We show typical features of PADs determined by acceleration of the ambient thermal electrons up to suprathermal energies in single RCSs and dynamical plasmoids. Our study suggests that locally-accelerated suprathermal electrons co-exist with those of solar origin. Therefore, some heat flux dropout and bi-directional strahl events observed in the heliosphere can be explained by local dynamical processes involving magnetic reconnection. Possible implications of the results for the interpretation of the strahl/halo relative density change with heliocentric distance and puzzling features of suprathermal electrons observed at crossings of the heliospheric current sheet and cometary comas are also discussed.

How to cite: Khabarova, O., Zharkova, V., Xia, Q., and Malandraki, O.: Effects of local particle acceleration in the solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3711,, 2020.

EGU2020-11505 | Displays | ST1.1

MMS Observations of Ion Cyclotron Waves in the Solar Wind

Hanying Wei, Lan Jian, Daniel Gershman, and Christopher Russell

Although electromagnetic ion cyclotron waves (ICWs) have been observed in the solar wind by multiple missions at heliocentric distances from 0.3 to 1 AU, there are still open questions on the generation mechanisms for these waves. Detailed analysis of the plasma distribution is needed to examine whether these waves are possibly generated locally.

In the solar wind, there are mainly three types of ion-driven instabilities responsible for parallel-propagating ICWs: ion cyclotron instabilities driven by ion component with temperature anisotropies greater than 1, parallel firehose instabilities driven by ion temperature anisotropies smaller than 1, and ion/ion magnetosonic instabilities driven by the relative drift between two ion components. In the solar wind frame, the waves due to ion cyclotron instability have left-handed polarization, while the waves due to firehose and ion/ion magnetosonic instabilities have right-handed polarization. Depending on the wave propagation parallel or anti-parallel to the magnetic field, the wave frequencies in the spacecraft frame are Doppler shifted higher or lower even with reversed handness. With the plasma data from Magnetospheric Multiscale (MMS) mission, we can examine the possible unstable mode with dispersion analysis and check if the prediction agrees with the observed wave mode. If the plasma measurements of the local solar wind do not support the wave growth, the waves could be possibly generated remotely close to the Sun and propagate away from the source region and are also carried outward by the solar wind flow. If these waves are generated remotely closer to the Sun, the wave properties at different heliocentric distances would help us better understand their sources.

The MMS spacecraft spends long periods of its orbit in the “pristine” solar wind starting end of 2017. From the 2017 December data we find over a hundred events and 42 of them last longer than 10 minutes which are called ICW storm events, and the longest event captured lasted over 2 hours. Although only about 17 of them have the plasma data available, we can perform case studies on these events first to investigate the wave properties and possible plasma instabilities, which will help us investigate the wave generation mechanisms due to local or remote sources.

How to cite: Wei, H., Jian, L., Gershman, D., and Russell, C.: MMS Observations of Ion Cyclotron Waves in the Solar Wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11505,, 2020.

Magnetic helicity is a quantity describing the twist, writhe, and torsion of magnetic field lines and magnetic configurations . The concept of magnetic helicity has successfully been applied to characterize solar coronal processes. A conjecture about one approximation relation between free magnetic free energy and relative magnetic helicity in the MHD extreme state of solar corona has been proposed by using the concept of magnetic helicity conservation and Lie-Poisson mechanical structure of MHD. We use constant α force-free filed extrapolation to check out this relation. We also apply this relation to analyze the results from the simulations and observations. Such relation may be helpful to predict the solar activity like the solar flares and CMEs

How to cite: Yang, S., Buechner, J., and Zhang, H.: Relation between the magnetic free energy and relative magnetic helicity in the MHD extreme state of solar corona, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19255,, 2020.

We study the Solar Active Region (AR) 12673 in September 2017, which is the most flare productive AR in the solar cycle 24.  Observations from Goode Solar Telescope (GST) show the strong photospheric magnetic fields (nearly 6000 G) in polarity  inversion line (PIL) and apparent photospheric twist on September 6,  the day of X9.3 flare. Corresponding to the strong twist,   upflows are observed to last one day  at the center part of that section of PIL;  down flows are observed in two ends.  Transverse velocity fields are derived from flow tracking.   Both Non-Linear Force-Free Field (NLFFF) and Non-Force-Free Field (NFFF) extrapolations are carried out and compared to trace 3-D magnetic fields in corona. Combining with EOVSA, coronal magnetic fields between 1000 and 2000 gauss are found above the flaring PIL at the height range between 8 and 4Mm, outlining the structure of a fluxrope with sheared arcade.  The above magnetic and velocity fields, as well as thermal structure of corona, provide initial condition for further data-driven MHD simulation.

How to cite: Wang, H.: Three-Dimensional Magnetic and Velocity Structures of Active Region 12673, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2234,, 2020.

EGU2020-22028 | Displays | ST1.1

Analysis of Local Regimes of Turbulence generated by 3D Magnetic Reconnection

lucia sanna and Giovanni lapenta

The process of magnetic reconnection when studied in nature or when modeled in 3D simulations differs in one key way from the standard 2D paradigmatic cartoon: it is accompanied by many fluctuations in the electromagnetic fields and plasma properties. We developed a diagnostics to study the spectrum of fluctuations in the various regions around a reconnection site. We define the regions in terms of the local value of the flux function that determines the distance from the reconnection site, with positive values in the outflow and negative values in the inflow. We find that fluctuations belong to two very different regimes depending on the local plasma beta (defined as the ratio of plasma and magnetic pressures). The first regime develops in the reconnection outflows where beta is high and it is characterized by a strong link between plasma and electromagnetic fluctuations, leading to momentum and energy exchanges via anomalous viscosity and resistivity. But there is a second, low-beta regime: it develops in the inflow and in the region around the separatrix surfaces, including the reconnection electron diffusion region itself. It is remarkable that this low-beta plasma, where the magnetic pressure dominates, remains laminar even though the electromagnetic fields are turbulent.

[1] G. Lapenta et al 2020 ApJ 888 104,

How to cite: sanna, L. and lapenta, G.: Analysis of Local Regimes of Turbulence generated by 3D Magnetic Reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22028,, 2020.

EGU2020-18577 | Displays | ST1.1

Solar cycle variation of simple and complex active regions

Shabnam Nikbakhsh, Eija Tanskanen, Maarit Käpylä, and Thomas Hackman

Solar active regions (ARs) emerge on the Sun’s photosphere and they frequently produce flares and coronal mass ejections which are among major space weather drivers. Therefore, studying ARs can improve space weather forecast.

The Mount Wilson Classification has been used since 1919 in order to group groups ARs according to their magnetic structures. In this study, we investigated the magnetic classification of 4797 ARs and their cyclic variation, using our daily approach for the period of January 1996 to December 2018.

We show that the monthly number of the simple ARs (SARs) attained their maximum during first peak of the solar cycle, whereas more complex ARs (CARs) reached their maximum roughly two years later, during the second peak of the cycle. We also demonstrate that the total abundance of CARs is very similar during a period of four years around their maximum number. We also studied the latitudinal distributions of SARs and CAR in northern and southern solar hemispheres and show that the independent of the complexity type, the distributions are the same in both hemispheres.

Furthermore, we investigated the earlier claim of increase in number of CARs due to the decrease in ARs latitudinal band. Here we show that, contrary to this claim, CARs attained their maximum number before the latitudinal band started to decrease in both northern and southern hemispheres.

How to cite: Nikbakhsh, S., Tanskanen, E., Käpylä, M., and Hackman, T.: Solar cycle variation of simple and complex active regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18577,, 2020.

EGU2020-2360 | Displays | ST1.1

Continuous components of solar activity oscillation spectrum and forecasting of solar activity

Dmitry Sokoloff, Peter Frick, Rodion Stepanov, and Frank Stefani

Spectrum of solar activity oscillations contains apart from the well-known 11-year activity cycle a continuous component, which includes, in particular, quasy-biennual oscillations as well as long-term oscillations including so-called Gleisberg cycle.  We suggest to consider the mid-term solar variability in terms of statistical dynamic of fully turbulent systems, where solid arguments are required to accept an isolated dominant frequency in a continuous (smooth) spectrum. What about the timescales longer than the Schwabe cycle, we consider them as a presence of long-term memory in solar dynamo and discuss statistical test for veryication of this interpretation. Sequences for statistical long-term forecast of solar activity are discussed.

How to cite: Sokoloff, D., Frick, P., Stepanov, R., and Stefani, F.: Continuous components of solar activity oscillation spectrum and forecasting of solar activity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2360,, 2020.

EGU2020-10225 | Displays | ST1.1

Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode

Junho Shin, Takashi Sakurai, Ryouhei Kano, Yong-Jae Moon, and Yeon-Han Kim

The X-Ray Telescope (XRT) onboard the Hinode satellite has a specially designed Wolter type grazing-incidence (GI) optics with a paraboloid-hyperboloid mirror assembly to measure the solar coronal plasma of temperatures up to 10 MK with a resolution of about one arcsec. One of the main purposes of this scientific mission is to investigate the detailed mechanism of energy transfer processes from the photosphere to the upper coronal region leading to its heating and the solar wind acceleration. To theoretically model the three-dimensional coronal structures is sensitive to the values of plasma properties at the base of solar corona and thus requires beforehand accurate empirical description of those properties. Though the telescope has provided unprecedented observations of solar corona for more than a decade, due to a wide field of view of 34 x 34 arcmin covering the full Sun, the optical performance of the instrument gradually deteriorates as it goes away from the optical center. For this reason, the off-axis characteristics of Hinode/XRT should be examined with care in order to precisely interpret the coronal plasma properties near the solar limb area.

This presentation will explain the importance of accurate calibration of the optical characteristics, especially for the data taken in the off-axis region. Our previous study has shown that the scattered light caused by the XRT mirror surface roughness has a power-law distribution and also shows an energy dependence, with which the PSF profile from the core to the scattering wing has been completed. We will introduce in this study how the level of scattering wing can be determined quantitatively for each focal plane filter from in-flight data analysis. We have also evaluated the vignetting effect in Hinode/XRT by analyzing the 2D distribution of effective area in the field of view taken from MSFC/XRCF pre-launch experiment. It is revealed that, unlike the case of Yohkoh/SXT, the degree of offset of an optical center is not serious and thus shows little deviation from rotational symmetry. Also important is that the vignetting pattern in XRT shows an energy dependence, which has never been considered before for the analyses of XRT data. More interesting results on the calibration of Hinode/XRT scattered light and the correction of vignetting effect will be introduced and discussed thoroughly. 

How to cite: Shin, J., Sakurai, T., Kano, R., Moon, Y.-J., and Kim, Y.-H.: Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10225,, 2020.

EGU2020-8298 | Displays | ST1.1

Solar Particle Radiation Storms Forecasting and Analysis - The HESPERIA tools

Olga Malandraki, Bernd Heber, Patrick Kuehl, Marlon Núñez, Arik Posner, Michalis Karavolos, and Nikos Milas

Solar Energetic Particles (SEPs), ranging in energy from tens of keV to a few GeV, constitute an important con-tributor to the characterization of the space environment. SEP radiation storms may have durations from a period of hours to days or even weeks and have a large range of energy spectrum profiles. They pose a threat to mod-ern technology strongly relying on spacecraft and are a serious radiation hazard to humans in space, and are additionally of concern for avionics and commercial aviation in extreme cases. The High Energy Solar Particle Events forecasting and Analysis (HESPERIA) project, supported by the HORIZON 2020 programme of the Eu-ropean Union, has furthered our prediction capability of high-energy SEP events by developing new European capabilities for SEP forecasting and warning, while exploiting novel as well as already existing datasets. The HESPERIA UMASEP-500 tool makes real-time predictions of the occurrence of >500 MeV and Ground Level Enhancement (GLE) events from the analysis of soft X-ray flux and high-energy differential proton flux measured by the GOES satellite network. Regarding the prediction of GLE events for the period 2000-2016, this tool had a Probability of Detection (POD) of 53.8% and a False Alarm Ratio (FAR) of 30.0%. For this period, the tool obtained an Advanced Warning Time (AWT) of 8 min taking as reference the alert time from the first NMstation; using the time of the warning issued by the GLE Alert Plus tool for the aforementioned period as reference, the tool obtained an AWT of 15 min (Núñez et al. 2017). Based on the Relativistic Electron Alert System for Exploration (REleASE) forecasting scheme (Posner, 2007), the HESPERIA REleASE tools generate real-time predictions of the proton flux (30-50 MeV) at the Lagrangian point L1, making use of relativistic electrons (v>0.9c) and near-relativistic (v<0.8c) electron measurements provided by the SOHO/EPHIN and ACE/EPAM experiments, respectively. Analysis of historic data from 2009 to 2016 has shown the HESPERIA REleASE tools have a low FAR (∼30%) and a high POD (63%). Both HESPERIA tools are operational through the project’s website ( at the National Observatory of Athens and presented in the recently published book on 'Solar Particle Radiation Storms Forecasting and Analysis, The HESPERIA HORIZON 2020 Project and Beyond', edited by Malandraki and Crosby, Springer, Astrophysics and Space Sciences Library, 2018, freely available at The HESPERIA tools have been selected as a top priority internationally by NASA/CCMC to be included in the simulations of the manned-mission to Mars by Johnson Space Center (ISEP project). The National Observatory of Athens participates in the ISEP project with a relevant contract.

How to cite: Malandraki, O., Heber, B., Kuehl, P., Núñez, M., Posner, A., Karavolos, M., and Milas, N.: Solar Particle Radiation Storms Forecasting and Analysis - The HESPERIA tools , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8298,, 2020.

EGU2020-5259 | Displays | ST1.1

EUHFORIA in the ESA Virtual Space Weather Modelling Centre

Stefaan Poedts

The goal of the ESA project "Virtual Space Weather Modelling Centre - Part 3" (2019-2021) is to further develop the Virtual Space Weather Modelling Centre (VSWMC), building on the Part 2 prototype system and focusing on the interaction with the ESA SSA SWE system. A first, limited version went operational in May 2019 under the H-ESC umbrella on the ESA SSA SWE Portal. The objective and scopes of this new project include: the efficient integration of new models and new model couplings, including daily automated end-to-end (Sun to Earth) simulations, the further development and wider use of the coupling toolkit  and front-end GUI, making the operational system more robust and user-friendly. The VSWMC-Part 3 project started on 1 October 2019.

EUHFORIA (‘European heliospheric forecasting information asset’) is integrated in the VSWMC and will be upgraded with alternative coronal models (Multi-VP and Wind-Predict) and flux-rope CME models, and new couplings will be made available, e.g. to more advanced magnetospheric models and radiation belt models, geo-effects models, and even SEP models. The first results will be discussed and put into perspective.

How to cite: Poedts, S.: EUHFORIA in the ESA Virtual Space Weather Modelling Centre, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5259,, 2020.

So far, most studies on the structure of coronal mass ejections (CMEs) are conducted through white-light coronagraphs, which demonstrate about one third of CMEs exhibit the typical three-part structure in the high corona (e.g., beyond 2 Rs), i.e., the bright front, the dark cavity and the bright core. In this presentation, we address the CME structure in the low corona (e.g., below 1.3 Rs) through extreme-ultraviolet (EUV) passbands and find that the three-part CMEs in the white-light images can possess a similar three-part appearance in the EUV images, i.e., a leading edge, a low-density zone, and a filament or hot channel. The analyses identify that the leading edge and the filament or hot channel in the EUV passbands evolve into the front and the core later within several solar radii in the white-light passbands, respectively. What's more, we find that the CMEs without obvious cavity in the white-light images can also exhibit the clear three-part appearance in the EUV images, which means that the low-density zone in the EUV images (observed as the cavity in white-light images) can be compressed and/or transformed gradually by the expansion of the bright core and/or the reconnection of magnetic field surrounding the core during the CME propagation outward. Our study suggests that more CMEs can possess the clear three-part structure in their early eruption stage. The nature of the low-density zone between the leading edge and the filament or hot channel is discussed.

How to cite: Song, H.: The Structure of Solar Coronal Mass Ejections in the Extreme-Ultraviolet Passbands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4293,, 2020.

EGU2020-19496 | Displays | ST1.1

Segmentation of coronal features to understand the solar EIV and UV irradiance variability

Joe Zender, Rens van der Zwaart, Rangaiah Kariyappa, Luc Damé, and Gabriel Giono

The study of solar irradiance variability is of great importance in heliophysics, the Earth’s climate, and space weather applications. These studies require careful identifying, tracking and monitoring of features in the solar magnetosphere, chromosphere, and corona.  We studied the variability of solar irradiance for a period of 10 years (May 2010–January 2020) using the Large Yield Radiometer (LYRA), the Sun Watcher using APS and image Processing (SWAP) on board PROBA2, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) of on board the Solar Dynamics Observatory (SDO), and applied a linear model between the identified features and the measured solar irradiance by LYRA.

We used the spatial possibilistic clustering algorithm (SPoCA) to identify coronal holes, and a morphological feature detection algorithm to identify active regions (AR), coronal bright points (BPS), and the quite sun (QS) and segment coronal features from the EUV observations of AIA. The AIA segmentation maps were then applied on SWAP images, images of all AIA wavelengths, HMI line-of-sight (LOS) magnetograms, and parameters such as the intensity, fractional area, and contribution of ARs/CHs/BPs/QS features were computed and compared with LYRA irradiance measurements as a proxy for ultraviolet irradiation incident to the Earth atmosphere.

We modelled the relation between the solar disk features (ARs, CHs, BPs, and QS) applied to magnetrogram and EUV images against the solar irradiance as measured by LYRA and the F10.7 radio flux. To avoid correlation between different the segmented features, a principal component analysis (PCM) was done. Using the independent component, a straightforward linear model was used and corresponding coefficients computed using the Bayesian framework. The model selected is stable and coefficients converge well.

The application of the model to data from 2010 to 2020 indicates that both at solar cycle timeframes as well as shorter timeframes, the active region influence the EUV irradiance as measured at Earth. Our model replicates the LYRA measured irradiance well.

How to cite: Zender, J., van der Zwaart, R., Kariyappa, R., Damé, L., and Giono, G.: Segmentation of coronal features to understand the solar EIV and UV irradiance variability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19496,, 2020.

EGU2020-11425 | Displays | ST1.1

Evolution of the Alfvén Mach number associated with a coronal mass ejection shock

Ciara Maguire, Eoin Carley, Joseph McCauley, and Peter Gallagher

The Sun regularly produces large-scale eruptive events, such as coronal mass ejections (CMEs) that can drive shock waves through the solar corona. Such shocks can result in electron acceleration and subsequent radio emission in the form of a type II radio burst. However, the early-phase evolution of shock properties and its relationship to type II burst evolution is still subject to investigation. Here we study the evolution of a CME-driven shock by comparing three commonly used methods of calculating the Alfvén Mach number (MA), namely: shock geometry, a comparison of CME speed to a model of the coronal Alfvén speed, and the type II band-splitting method. We applied the three methods to the 2017 September 2 event, focusing on the shock wave observed in extreme ultraviolet (EUV) by the Solar Ultraviolet Imager (SUVI) on board GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph (LASCO) on board SOHO, and the type II radio burst observed by the Irish Low Frequency Array (I-LOFAR). We show that the three different methods of estimating shock MA yield consistent results and provide a means of relating shock property evolution to the type II emission duration. The type II radio emission emerged from near the nose of the CME when MA was in the range 1.4-2.4 at a heliocentric distance of 1.6 R. The emission ceased when the CME nose reached 2.4 R, despite an increasing Alfvén Mach number (up to 4). We suggest the radio emission cessation is due to the lack of quasi-perpendicular geometry at this altitude, which inhibits efficient electron acceleration and subsequent radio emission.

How to cite: Maguire, C., Carley, E., McCauley, J., and Gallagher, P.: Evolution of the Alfvén Mach number associated with a coronal mass ejection shock, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11425,, 2020.

EGU2020-1501 | Displays | ST1.1

Examination of the EUV Intensity in the Open Magnetic Field Regions Associated with Coronal Holes

Guan-Han Huang, Chia-Hsien Lin, and Lou Chuang Lee

Coronal holes can be identified as the regions with magnetic field lines extending far away from the Sun, or the darkest regions in EUV/X-ray images with predominantly unipolar magnetic fields. A comparison between the locations of our determined regions with open magnetic field lines (OMF) and regions with low EUV intensity (LIR) reveals that only 12% of the OMF regions coincide with the LIRs. The aim of this study is to investigate the conditions leading to the different brightnesses of OMF regions, and to provide a means to predict whether an OMF region would be bright or dark. Examining the statistical distribution profiles of the magnetic field expansion factor (fs) and Atmospheric Imaging Assembly 193 Å intensity (I193) reveals that both profiles are approximately log-normal. The analysis of the spatial and temporal distributions of fs and I193 indicates that the bright OMF regions often are inside or next to regions with closed field lines, including quiet-Sun regions and regions with strong magnetic fields. Examining the relationship between I193 and fs reveals a weak positive correlation between log I193 and log fs , with a correlation coefficient ≈ 0.39. As a first-order approximation, the positive relationship is determined to be log I193 = 0.62 log fs + 1.51 based on the principle of the whitening/dewhitening transformation. This linear relationship is demonstrated to increase the consistency between the OMF regions and LIRs from 12% to 23%.

How to cite: Huang, G.-H., Lin, C.-H., and Lee, L. C.: Examination of the EUV Intensity in the Open Magnetic Field Regions Associated with Coronal Holes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1501,, 2020.

EGU2020-4011 | Displays | ST1.1

On the Relation between Filament Chirality, Rotation Direction, and Morphology

Zhenjun Zhou, Rui Liu, Xing Cheng, Chaowei Jiang, Yuming Wang, Lijuan Liu, Guoqiang Wang, Tielong Zhang, and Jun Cui

Coronal mass ejections (CMEs) with enhanced south-component of the magnetic field are susceptible to producing geomagnetic storms. Filament chirality, rotation direction, and morphology are responsible for CMEs’ magnetic orientation and they are manifestations of magnetic helicity. However, different models predict different relations among them. In this paper, taking advantage of stereoscopic observations and a new method of determining the chirality of erupting filaments, we analyze 12 filaments that present a clear rotation during the eruption. The results based on the small sample support the argument that the filaments with for sinistral (dextral) chirality, they rotate clockwise (counterclock-wise), indicating the transformation of twist into writhe. Moreover, we also inspect soft X-ray and EUV hot temperature images and find that, the associated sigmoids are consistent with filaments prior to the eruption morphologically. However, once starting to rise up, the erupting filaments reverse their shapes from forward S-shaped to inversed S-shaped and vice versa.

How to cite: Zhou, Z., Liu, R., Cheng, X., Jiang, C., Wang, Y., Liu, L., Wang, G., Zhang, T., and Cui, J.: On the Relation between Filament Chirality, Rotation Direction, and Morphology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4011,, 2020.

EGU2020-6928 | Displays | ST1.1

Magnetic flux transport in the photosphere of the Sun

Dmitrii Baranov, Elena Vernova, Marta Tyasto, and Olga Danilova

On the basis of the synoptic maps of the photospheric magnetic field obtained by the National Solar Observatory Kitt Peak for 1978-2016, a latitude-time diagram of the magnetic field was built. When averaging intensity values over the heliolongitude, the magnetic field sign was taken into account. In order to consider the characteristics of the distribution of weak magnetic fields an upper limit of 5 G was set.

The latitude-time diagram clearly shows inclined bands corresponding to positive and negative polarity magnetic flows drifting towards the poles of the Sun. Two groups of flows are observed: 1. Relatively narrow bands, with alternating polarity, beginning near the equator and reaching almost the poles of the Sun. Along the time axis, the flow length of one polarity is on the order of 1-2 years; 2. short powerful flows, 3-4.5 years wide, propagating from the spot zone to the poles. These flows reach the poles simultaneously with the begin of the polar field reversal, apparently representing  the so-called “Rush to the Poles” phenomenon.

The pattern of magnetic field transport is significantly different for the northern and southern hemispheres. Alternating flows of positive and negative polarities most clearly appear in the southern hemisphere during periods of positive polarity of the southern polar field. For the northern hemisphere the picture is much less clear but for individual time intervals alternating flows of opposite polarities can be traced. The slopes of magnetic flux bands allow us to estimate the rate of meridional drift of magnetic fields, which was slightly different for the two hemispheres: V = (16±2) m/s for the southern hemisphere and V = (21±4) m/s for the northern hemisphere. The results obtained indicate that the distribution of weak magnetic fields over the surface of the Sun has a complex structure that is different for the two hemispheres and varies from cycle to cycle.

How to cite: Baranov, D., Vernova, E., Tyasto, M., and Danilova, O.: Magnetic flux transport in the photosphere of the Sun, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6928,, 2020.

EGU2020-9247 | Displays | ST1.1

Data-driven modelling of erupting solar active regions

Daniel Price, Jens Pomoell, Erkka Lumme, and Emilia Kilpua

Fully understanding solar eruptions and their eventual consequences for the Earth requires a rigorous modelling approach due to the difficulty of directly measuring magnetic fields in the solar corona. Consequently, this study employs a time-dependent data-driven magnetofrictional model (TMFM) to simulate the coronal evolution of coronal mass ejections from multiple active regions. We processed HMI vector magnetograms with the Electric Field Inversion Toolkit to generate a time series of photospheric electric field maps which were used as the lower boundary to drive our TMFM simulations. Analysis was aided by computing maps of the squashing factor and twist, as well as by calculating coronal metrics such as the volume energy and helicity, and by comparison to AIA observations. Studying multiple events simultaneously permits comparative analysis and the evaluation of the model performance.

How to cite: Price, D., Pomoell, J., Lumme, E., and Kilpua, E.: Data-driven modelling of erupting solar active regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9247,, 2020.

EGU2020-22351 | Displays | ST1.1

Quasi Periodic Oscillations in the Pre Phases of Recurrent Jets Highlighting Plasmoids in Current Sheet

Reetika Joshi, Ramesh Chandra, Brigitte Schmieder, Guillaume Aulanier, Pooja Devi, Fernando Moreno-Insertis, and Daniel Nóbrega-Siverio

Solar jets observed at the limb are important to determine the location of reconnection sites in the corona. In this study, we investigate six recurrent hot and cool jets occurring in the active region NOAA 12644 as it is crossing the west limb on April 04, 2017. These jets are observed in all the UV/EUV filters of SDO/AIA and in cooler temperature formation lines in IRIS slit jaw images. The jets are initiated at the top of a double chamber vault with cool loops on one side and hot loops on the other side. The existence of such double chamber vaults suggests the presence of emerging flux with cool loops, the hot loops being the reconnected loops similarly as in the models of Moreno-Insertiset al. 2008, 2013 and Nóbrega-Siverio et al. 2016. In the preliminary phase of the main jets, quasi periodic intensity oscillations accompanied by smaller jets are detected in the bright current sheet between the vault and the preexisting magnetic field. Individual kernels and plasmoids are ejected in open field lines along the jets. Plasmoids may launch torsional Alfven waves and the kernels would be the result of the untwist of the plasmoids in open magnetic field as proposed in the model of Wyper et al. 2016.

How to cite: Joshi, R., Chandra, R., Schmieder, B., Aulanier, G., Devi, P., Moreno-Insertis, F., and Nóbrega-Siverio, D.: Quasi Periodic Oscillations in the Pre Phases of Recurrent Jets Highlighting Plasmoids in Current Sheet, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22351,, 2020.

EGU2020-20365 | Displays | ST1.1

Abrupt shrinking of solar corona in late 1990s and related changes in solar magnetic structure

Kalevi Mursula, Ilpo Virtanen, Jennimari Koskela, and Ismo Tähtinen

Several studies have noted on changes in the properties of sunspots, and in the mutual relations between various global parameters of solar magnetic activity (e.g. UV/EUV irradiance, radio and IR emissions, TSI/SSI), as well as between solar and ionospheric parameters since the onset of solar cycle 23. These changes have been suggested to be related to the overall reduction of solar activity at the aftermath of the decline of the Grand modern maximum of solar activity that prevailed during most of the 20th century. We have recently derived the longest record of coronal magnetic field intensities since 1968 using Mount Wilson Observatory and Wilcox Solar Observatory observations of the photospheric magnetic field and the PFSS model, and compared it with the heliospheric magnetic field observed at the Earth. We found that the time evolution of the coronal magnetic field during the last 50 years agrees with the heliospheric magnetic field only if the effective coronal size, the distance of the coronal source surface of the heliospheric magnetic field, is allowed to change in time. We calculated the optimum distance for each solar rotation and found that it experienced an abrupt decrease in the late 1990s. The effective volume of the solar corona shrunk to less than one half of its previous value during a short period of only a few years. This shrinking was related with a systematic change in the structure of the coronal magnetic field during the same time interval. We review these dramatic changes in the solar corona and discuss their possible connection to the changes in the different solar activity parameters and the reduction of the overall solar activity.

How to cite: Mursula, K., Virtanen, I., Koskela, J., and Tähtinen, I.: Abrupt shrinking of solar corona in late 1990s and related changes in solar magnetic structure, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20365,, 2020.

EGU2020-21894 | Displays | ST1.1

Propagation of a Solar Moving Type IV Radio Burst Using LOFAR

Hongyu Liu, Pietro Zucca, Jasmina Magdalenic, Peijin Zhang, and Kyungsuk Cho

Type IV radio burst is the long-lasting broadband continuum emission in metric wave-length. In addition to the continuum emission Type IV radio bursts may show fine structure with high brightness temperature. The physical emission responsible for both continuum and fine structures is still under debate. In this study, we present a moving type IV radio burst observed by LOFAR. We performed a detailed comparison of NRH and LOFAR imaging. Using the full stokes parameterss from the LOFAR dynamic spectra, we have also calculated the degree of circular polarisation during the propagation of the moving type IV. Finally, we combined LOFAR interferometric data with SDO-AIA and LASCO-C2 to track the evolution of this type IV and relate it with the CME.

How to cite: Liu, H., Zucca, P., Magdalenic, J., Zhang, P., and Cho, K.: Propagation of a Solar Moving Type IV Radio Burst Using LOFAR, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21894,, 2020.

EGU2020-80 | Displays | ST1.1

Source size and Position of a Type IIIb-III Pair with LOFAR

Peijin Zhang, Pietro Zucca, Sarrvesh Sridhar, and Chuanbing Wang

Solar radio bursts originate mainly from high energy electrons accelerated by solar eruptions like solar flares, jets, and coronal mass ejections (CMEs).  A sub-category of solar radio bursts with a short time duration may be used as a proxy to understand the wave generation and propagation within the corona.  Complete case studies of the source size, position, and kinematics of short-term bursts are very limited due to instrumental limitations.
LOw-Frequency-ARray (LOFAR) is an advanced radio antenna array. It is capable of a variety of processing operations including correlation for standard interferometric imaging, the tied-array beam-forming, and the real-time triggering on incoming station data-streams. With recently upgraded LOFAR, we can achieve high spatial and temporal imaging for solar radio bursts.
Here we present a detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging, the radio source of a type IIIb-III pair was imaged with the interferometric mode using the remote baselines of the (LOFAR). This study shows how the fundamental and harmonic components have a significant different source motion.  The apparent source of the fundamental emission at 26 MHz is about 4 times the speed of light, while the apparent source of the harmonic emission shows a speed of < 0.02 c.  We show that the apparent speed of the fundamental source is more affected by the scattering and refraction of the coronal medium.

How to cite: Zhang, P., Zucca, P., Sridhar, S., and Wang, C.: Source size and Position of a Type IIIb-III Pair with LOFAR, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-80,, 2020.

EGU2020-7374 | Displays | ST1.1

Interferometric Observations of the Active Regions in Radio Domain Before and After the Total Solar Eclipse on 21 August 2017

Bartosz Dabrowski, Paweł Flisek, Christian Vocks, Diana Morosan, Peijin Zhang, Pietro Zucca, Jasmina Magdalenic, Richard Fallows, Andrzej Krankowski, Gottfried Mann, Leszek Blaszkiewicz, Pawel Rudawy, Marcin Hajduk, Adam Fron, Peter Gallagher, Aoife Maria Ryan, Kacper Kotulak, and Barbara Matyjasiak

We hereby present the interferometric LOFAR observations made before and after the total solar eclipse on 21 August 2017, during which the type III radio bursts have been detected.

The LOw-Frequency ARray (LOFAR) is a large radio interferometer operating in the frequency range of 10–240 MHz, designed and constructed by ASTRON (the Netherlands Institute for Radio Astronomy). The LOFAR telescope is an array of stations distributed throughout the Netherlands and other parts of Europe. Currently the system consist of 52 LOFAR stations located in Europe. Apart from the high time and frequency resolution of the dynamic spectra, LOFAR allows also a 2D imaging of the radio sources and tracking of their positions through the solar corona.

In this work we present a preliminary analysis of the dynamic spectra of type III radio bursts with radio images.

How to cite: Dabrowski, B., Flisek, P., Vocks, C., Morosan, D., Zhang, P., Zucca, P., Magdalenic, J., Fallows, R., Krankowski, A., Mann, G., Blaszkiewicz, L., Rudawy, P., Hajduk, M., Fron, A., Gallagher, P., Ryan, A. M., Kotulak, K., and Matyjasiak, B.: Interferometric Observations of the Active Regions in Radio Domain Before and After the Total Solar Eclipse on 21 August 2017, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7374,, 2020.

EGU2020-13366 | Displays | ST1.1

Near real time plasma irregularity monitoring by FORMOSAT-7/COSMIC-2

ShihPing Chen, Charles C. Lin, Rajesh Panthalingal Krishnanunni, Richard Eastes, and Jong-Min Choi

The near real-time global plasma bubble map is constructed by utilizing the FORMOSAT-7/COSMIC-2(F7/C2) radio occultation(RO) scintillation observations in low latitudes. Several tools investigating plasma bubbles like the rate of TEC index(ROTI), Range-Time-Intensity(RTI) diagrams of the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere(JULIA), and the Global-scale Observations of the Limb and Disk(GOLD) 135.6nm airglow observations are provided validating the RO scintillations. Result shows that the F7/C2 scintillation is sensitive detecting plasma irregularities, especially for the bottom side of these bubbles, which can be used to investigating nighttime vertical plasma drifts in low latitudinal F-region. The hourly quick look of the low latitude plasma bubble occurrence and vertical ion drift around the globe is significant to the space weather monitoring.

How to cite: Chen, S., Lin, C. C., Panthalingal Krishnanunni, R., Eastes, R., and Choi, J.-M.: Near real time plasma irregularity monitoring by FORMOSAT-7/COSMIC-2, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13366,, 2020.

EGU2020-4747 | Displays | ST1.1

Bimodal distribution of the solar wind using data from ACE spacecraft.

Carlos Larrodera and Consuelo Cid

The main goal of this work is to separate the behavior of the two types of quiet solar wind at 1 AU: fast and slow.
Our approach is a bi-Gaussian distribution function, formed by the addition of two Gaussian distribution functions, where each one represents one type of wind. We check our approach by fitting the bi-Gaussian to data from ACE spacecraft. We use level 2 data measured during solar cycles 23 and 24 of different solar wind parameters, including proton speed, proton temperature, density and magnetic field. Our results show that the approach is fine and only transient events departs from the proposed function. Moreover, we can show bi modal behavior of the solar wind at 1 AU, not only for the proton speed, but also for the other analyzed parameters. We also check the solar cycle dependence of the different fitting parameters.

How to cite: Larrodera, C. and Cid, C.: Bimodal distribution of the solar wind using data from ACE spacecraft., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4747,, 2020.

EGU2020-19262 | Displays | ST1.1

Comparing the boundaries of interplanetary coronal mass ejections

Consuelo Cid, Carlos Larrodera, and Elena Saiz

The boundaries of interplanetary coronal mass ejections (ICMEs) are commonly established based on the magnetic field smoothness and/or the low temperature, when compared to normal solar wind. Based on the analysis of the ICME on 2015 January 6-7, observed by Wind and ACE spacecraft, Cid et al. (2016) proposed compositional signatures as the most precise diagnostic tool for the boundaries of ICMEs. Having as a starting point the ICMEs catalogues from Jian et al. (2006) and Richardson and Cane (2010), and the Wind spacecraft ICME catalogue on the NASA web site, we have compared the boundaries of all ICMEs observed by the ACE spacecraft attending to different signatures. This contribution shows the results of the study.

How to cite: Cid, C., Larrodera, C., and Saiz, E.: Comparing the boundaries of interplanetary coronal mass ejections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19262,, 2020.

EGU2020-21663 | Displays | ST1.1

Axial dipole moments of solar active regions in cycles 21-24

Iiro Virtanen, Ilpo Virtanen, Alexei Pevtsov, and Kalevi Mursula

The axial dipole moments of emerging active regions control the evolution of the axial dipole moment of the whole photospheric magnetic field and the strength of polar fields. Hale's and Joy's laws of polarity and tilt orientation affect the sign of the axial dipole moment of an active region, determining the normal sign for each solar cycle. If both laws are valid (or both violated), the sign of the axial moment is normal. However, for some active regions, only one of the two laws is violated, and the signs of these axial dipole moments are the opposite of normal. The opposite-sign axial dipole moments can potentially have a significant effect on the evolution of the photospheric magnetic field, including the polar fields.

We determine the axial dipole moments of active regions identified from magnetographic observations and study how the axial dipole moments of normal and opposite signs are distributed in time and latitude in solar cycles 21-24.We use active regions identified from the synoptic maps of the photospheric magnetic field measured at the National Solar Observatory (NSO) Kitt Peak (KP) observatory, the Synoptic Optical Long term Investigations of the Sun (SOLIS) vector spectromagnetograph (VSM), and the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO).

We find that, typically, some 30% of active regions have opposite-sign axial dipole moments in every cycle, often making more than 20% of the total axial dipole moment. Most opposite-signed moments are small, but occasional large moments, which can affect the evolution of polar fields on their own, are observed. Active regions with such a large opposite-sign moment may include only a moderate amount of total magnetic flux. We find that in cycles 21-23 the northern hemisphere activates first and shows emergence of magnetic flux over a wider latitude range, while the southern hemisphere activates later, and emergence is concentrated to lower latitudes. We also note that cycle 24 differs from cycles 21-23 in many ways. Cycle 24 is the only cycle where the northern butterfly wing includes more active regions than the southern wing, and where axial dipole moment of normal sign emerges on average later than opposite-signed axial dipole moment. The total axial dipole moment and even the average axial moment of active regions is smaller in cycle 24 than in previous cycles.

How to cite: Virtanen, I., Virtanen, I., Pevtsov, A., and Mursula, K.: Axial dipole moments of solar active regions in cycles 21-24, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21663,, 2020.

EGU2020-15185 | Displays | ST1.1

Stochastic Resonance could explain Recurrence of Grand Minima

Carlo Albert and Simone Ulzega

Proxies of solar activity have revealed repeated Grand Minima that occur with a certain regularity associated with the well-known Gleissberg and Süss/deVries cycles. These and other prominent cycles in the spectrum of solar activity are also seen in the spectrum of the planetary torque exerted on the solar tachocline, which has revived the hypothesis of a planetary influence on solar activity. It is not clear, however, how the extremely weak planetary forcing could influence the solar magnetic activity. Here, we suggest that stochastic resonance could explain the necessary amplification of the forcing and provide numerical evidence from stochastic time-delayed dynamo models. If the intrinsic noise of the solar dynamo allows for a frequent switching between active and quiescent stable states, tiny periodic forcings can be greatly amplified, provided the dynamo is poised close to a critical point. Such a forcing could be caused by a tidal modulation of the minimal magnetic field required for flux-tube buoyancy.

How to cite: Albert, C. and Ulzega, S.: Stochastic Resonance could explain Recurrence of Grand Minima, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15185,, 2020.

ST1.2 – Multi-spacecraft Measurements in the Inner Heliosphere on Various Scales

EGU2020-13664 | Displays | ST1.2

Radial evolution of magnetic field fluctuations in an ICME sheath

Simon Good, Matti Ala-Lahti, Erika Palmerio, Emilia Kilpua, and Adnane Osmane

The sheaths of compressed solar wind that precede interplanetary coronal mass ejections (ICMEs) commonly display large-amplitude magnetic field fluctuations. As ICMEs propagate radially from the Sun, the properties of these fluctuations may evolve significantly. We present a case study of an ICME sheath observed by a pair of radially aligned spacecraft at around 0.5 and 1 AU from the Sun. Radial changes in fluctuation amplitude, compressibility, inertial-range spectral slope, permutation entropy, Jensen-Shannon complexity, and planar structuring are characterised.  We discuss the extent to which the observed evolution in the fluctuations is similar to that of solar wind emanating from steady sources at quiet times, how the evolution may be influenced by evolving local factors such as leading-edge shock orientation, and how the perturbed heliospheric environment associated with ICME propagation may impact the evolution more generally.

How to cite: Good, S., Ala-Lahti, M., Palmerio, E., Kilpua, E., and Osmane, A.: Radial evolution of magnetic field fluctuations in an ICME sheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13664,, 2020.

EGU2020-6043 | Displays | ST1.2

Multi-spacecraft Observations of interacting CME flux ropes

Emilia Kilpua, Simon Good, Erika Palmerio, Eleanna Asvestari, Jens Pomoell, Erkka Lumme, Matti Ala-Lahti, Milla Kalliokoski, Diana Morosan, Daniel Price, Jasmina Magdalenic, Stefaan Poedts, and Yoshimi Futaana

Interactions between coronal mass ejections (CMEs) in interplanetary space are a highly important aspect for understanding their physical dynamics and evolution as well as their space weather consequences. Here we present an analysis of three CMEs that erupted from the Sun on June 12-14, 2012 using almost radially aligned spacecraft at Venus and Earth, complemented by heliospheric imaging and modelling with EUHFORIA. These multi-spacecraft observations were critical for interpreting the event correctly, in particular regarding the last two CMEs in the series (June 13 and June 14). At the orbit of Venus these CMEs were mostly separate with the June 14 CME just about to reach the previous CME. A significant interaction occurred before the CMEs reached the Earth. The shock of the June 14 CME had propagated through the June 13 CME and the two CMEs had coalesced into a single large flux rope structure before they reached the Earth. This merged flux rope had one of the largest magnetic field magnitudes observed in the near-Earth solar wind during Solar Cycle 24. We discuss also the general importance of multi-spacecraft observations and modelling using them in analyzing solar eruptions.

How to cite: Kilpua, E., Good, S., Palmerio, E., Asvestari, E., Pomoell, J., Lumme, E., Ala-Lahti, M., Kalliokoski, M., Morosan, D., Price, D., Magdalenic, J., Poedts, S., and Futaana, Y.: Multi-spacecraft Observations of interacting CME flux ropes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6043,, 2020.

EGU2020-2736 | Displays | ST1.2

(Non)-radial propagation of the solar wind flow

Zdeněk Němeček, Tereza Ďurovcová, Jana Šafránková, Jiří Šimůnek, John D. Richardson, and Jaroslav Urbář

The solar wind aberration due to non-radial velocity components and the Earth orbital motion is important for the overall magnetosphere geometry because the magnetospheric tail is aligned with the solar wind flow. This paper investigates an evolution of non-radial components of the solar wind flow along the path from the Sun to 6 AU. A comparison of observations at 1 AU and closer to or further from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Wind, ACE, Spektr-R, THEMIS B and C, Helios 1 and 2, Mars-Express, Voyager 1 and 2) shows that (i) the average values of non-radial components vary with the distance from the Sun and (ii) they differ according to solar wind streams.

How to cite: Němeček, Z., Ďurovcová, T., Šafránková, J., Šimůnek, J., Richardson, J. D., and Urbář, J.: (Non)-radial propagation of the solar wind flow , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2736,, 2020.

EGU2020-8621 | Displays | ST1.2

Multi-point observations of a reconnection outflow associated with interacting flux ropes in the solar wind

Zoltan Vörös, Emiliya Yordanova, Owen Roberts, and Yasuhito Narita

Twisted magnetic flux ropes embedded in an interplanetary coronal mass ejection (ICME) often contain oppositely oriented magnetic fields and potentially reconnecting current sheets. Reconnection outflows in the solar wind can be identified through magnetic field and plasma signatures, for example, through decreasing magnetic field magnitude, enhanced bulk velocity, temperature and (anti)correlated rotations of the magnetic field and plasma velocity. We investigate a reconnection outflow observed by ACE, WIND and Geotail spacecraft within the interaction region of two flux ropes embedded into an ICME. The SOHO spacecraft, located 15 RE upstream, 120 RE in GSE Y and 5 RE in GSE Z direction from the ACE spacecraft, does not see any plasma signatures of the reconnection outflow. At the same time the other spacecraft, also separated by more than 200 RE in X and Y GSE directions, observe strong plasma and magnetic field fluctuations at the border of the exhaust.  The fluctuations could be associated with Kelvin-Helmholtz (KH) instability at the border of the reconnection outflow with strong flow shear.  It is speculated that the KH instability driven fluctuations and dissipation is responsible for stopping the reconnection outflow which is therefore not seen by SOHO.

How to cite: Vörös, Z., Yordanova, E., Roberts, O., and Narita, Y.: Multi-point observations of a reconnection outflow associated with interacting flux ropes in the solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8621,, 2020.

EGU2020-18966 | Displays | ST1.2

Kinetic models of current sheets in the solar wind

Thomas Neukirch, Ivan Vasko, Anton Artemyev, and Oliver Allanson

Current sheets in the collisionless solar wind usually have kinetic spatial scales. In-situ measurements (e.g. by Artemis) show that these current sheets are often approximately force-free, i.e. the directions of their current density and magnetic field are aligned, despite the fact that the plasma β is found to be of the order of one. The measurements also often show systematic asymmetric spatial variations of the plasma density and temperature across the current sheets, whilst the plasma pressure is approximately uniform. We present analytical equilibrium distribution functions of self-consistent force-free collisionless current sheets which allow for asymmetric plasma density and temperature gradients.

How to cite: Neukirch, T., Vasko, I., Artemyev, A., and Allanson, O.: Kinetic models of current sheets in the solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18966,, 2020.

STEREO has provided over 10 yr of continuous monitoring of CMEs and CME-driven shock waves from the Sun to Earth-like distances, as well as multipoint measurements of SEPs in the keV to 100 MeV energy range. These observations have revealed a number of puzzling properties of SEPs. For instance, gradual and impulsive SEP events have been measured over extended ranges of longitudes by STEREO, sometimes extending over 360 degrees around the Sun. Multi-spacecraft remote-sensing observations have allowed us to perform shock wave modeling in 3D, and to derive and examine consistently critical shock parameters during their evolution. I will present a connection of the shocks/CMEs to SEP properties from multi-spacecraft in-situ measurements by alleviating projection effects, accounting for both the complexities of coronal shocks and how they are likely to connect magnetically with in-situ spacecraft. A comparison between the shock wave parameters derived from 3D modeling and observations, and SEP characteristics confirm predictions of diffusive shock acceleration, that efficient acceleration of SEPs should naturally occur at shock regions where the shock Mach number is high. I will also discuss how modeling shock waves and estimating their magnetic connectivity can be useful in future studies to determine the solar origin of particle events measured by Parker Solar Probe.

How to cite: Kouloumvakos, A. and Rouillard, A. P.: Shock wave properties in the solar corona and their associations with multi-spacecraft solar energetic particle events measured near 1AU., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11889,, 2020.

EGU2020-21246 | Displays | ST1.2

Energetic particles measurements on the lunar far-side by Lunar Lander Neutron and Dosimetry(LND) experiment

Zigong Xu, Robert F Wimmer-Schweingruber, Jingnan Guo, Jia Yu, Shenyi Zhang, Thomas Berger, Daniel Matthiae, Soenke Burmeister, Stephan Boettcher, and Bernd Heber

After Chang’E 4 successfully landed on the far side of the moon on Jan 3rd, 2019, the Lunar Lander Neutron and Dosimetry experiment has been working for 13 lunar days from January, 2019 to January, 2020, sending back the measurements of dose, linear energy transfer (LET) spectrum, neutrons, and charged particles. Here, we show observations of charged particles especially protons and Helium ions during quiet time. We also present two solar energetic particle events registered by LND in May 2019, which are also the first such measurements on the far-side surface of the moon. The temporal variations of particle fluxes on the far side of the moon detected by LND provide a new observation site in space and can be helpful to improve our understanding of particle propagation and transport in the heliosphere.


How to cite: Xu, Z., Wimmer-Schweingruber, R. F., Guo, J., Yu, J., Zhang, S., Berger, T., Matthiae, D., Burmeister, S., Boettcher, S., and Heber, B.: Energetic particles measurements on the lunar far-side by Lunar Lander Neutron and Dosimetry(LND) experiment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21246,, 2020.

EGU2020-3690 | Displays | ST1.2

Long-term properties of the solar wind and their relation to solar cycles

Anna Salohub, Jana Šafránkova, Zdeněk Němeček, Lubomír Přech, and Tereza Ďurovcová

The solar wind variations during particular solar cycles have been described in many previous studies including the solar cycle 23 that was characterized by a long, deep, and very complex solar minimum with very low values of many solar wind parameters.

Using statistical methods, we analyzed 25 years of Wind spacecraft measurements with motivation to reveal differences and similarities in magnetic field components and solar wind plasma parameters in individual solar cycles. We tracked the changes of the solar magnetic field strength, and components, solar wind speed, density, dynamic pressure, temperature, and composition). Except quiet solar wind conditions during solar minima and maxima, we also selected significant discontinuities (ICME and CIRs) and investigated their influence on profiles of average parameters. For this, we followed other quantities connected with their presence as their average front normals, regions of transitions between high and slow wind streams, special interplanetary magnetic field orientations, etc.). We discuss a behavior of investigated parameters over solar cycles as well as on shorter time scales (in the order of days and hours).

How to cite: Salohub, A., Šafránkova, J., Němeček, Z., Přech, L., and Ďurovcová, T.: Long-term properties of the solar wind and their relation to solar cycles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3690,, 2020.

EGU2020-7451 | Displays | ST1.2

Solar wind radial evolution via future multi-spacecraft in-situ observations

Štěpán Štverák, Milan Maksimovic, Petr Hellinger, and Pavel M. Trávníček

Our understanding of the solar wind evolution, its energy budget, and role of the key mechanisms providing the energy exchange between the plasma particles and electromagnetic fluctuations along the expansion, is highly limited by the single point nature of most in situ spacecraft measurements. Obviously it is difficult to observe and track the individual processes in space and time from this narrow perspective. One way to improve our knowledge of these large-scale variations is to employ multi-spacecraft observations, namely rather rare so called line-up events where one can potentially observe the true evolution of individual solar wind plasma parcels. A pioneering work in this field was done using Helios I&II missions. Here we present an analyses of using such tool for future events predicted to be available from the very recent missions Parker Solar Probe and Solar Orbiter (and optionally BepiColombo).

How to cite: Štverák, Š., Maksimovic, M., Hellinger, P., and Trávníček, P. M.: Solar wind radial evolution via future multi-spacecraft in-situ observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7451,, 2020.

EGU2020-4009 | Displays | ST1.2

Radial Evolution of Coronal Mass Ejections in the Inner Heliosphere: Catalog and Analysis

Tarik Salman, Reka Winslow, and Noé Lugaz

Our knowledge of the properties of Coronal Mass Ejections (CMEs) in the inner heliosphere is constrained by the relative lack of plasma observations between the Sun and 1 AU. In this work, we present a comprehensive catalog of 47 CMEs measured in situ measurements by two or more radially aligned spacecraft (MESSENGER, Venus Express, STEREO, and Wind/ACE). We estimate the CME impact speeds at Mercury and Venus using a drag-based model and present an average propagation profile of CMEs (speed and deceleration/acceleration) in the inner heliosphere. We find that CME deceleration continues past Mercury's orbit but most of the deceleration occurs between the Sun and Mercury. We examine the exponential decrease of the maximum magnetic field strength in the CME with heliocentric distance using two approaches: a modified statistical method and analysis from individual conjunction events. Findings from both the approaches are on average consistent with previous studies but show significant event-to-event variability. We also find the expansion of the CME sheath to be well fit by a linear function. However, we observe the average sheath duration and its increase to be fairly independent of the initial CME speed, contradicting commonly held knowledge that slower CMEs drive larger sheaths. We also present an analysis of the 3 November 2011 CME observed in a longitudinal conjunction between MESSENGER, Venus Express, and STEREO-B focusing on the expansion of the CME and its correlation with the exponential fall-off of the maximum magnetic field strength in the ejecta.

How to cite: Salman, T., Winslow, R., and Lugaz, N.: Radial Evolution of Coronal Mass Ejections in the Inner Heliosphere: Catalog and Analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4009,, 2020.

EGU2020-13474 | Displays | ST1.2

Spatial coherence of interplanetary coronal mass ejection-driven sheaths at 1 AU

Matti Ala-Lahti, Julia Ruohotie, Simon Good, Emilia Kilpua, and Noé Lugaz

We report on the longitudinal coherence of sheath regions driven by interplanetary coronal mass ejections (ICMEs). ICME sheaths are significant drivers of geomagnetic activity at the Earth, with a considerable fraction of ICME-driven storms being either entirely or primarily induced by the sheath. Similarly to Lugaz et al. (2018; doi:10.3847/2041-8213/aad9f4), we have analyzed two-point magnetic field measurements made by the ACE and Wind spacecraft in 29 ICME sheaths to estimate the coherence scale lengths, defined as the spatial scale at which correlation between measurements falls to zero, of the field magnitude and components. Scale lengths for the sheath are found to be mostly smaller than the corresponding values in the ICME driver, an expected result given that ICME sheaths are characterized by highly fluctuating, variable magnetic fields, in contrast to the often more coherent ejecta. A relatively large scale length for the magnetic field component in the GSE y-direction was found. We discuss how magnetic field line draping around the ejecta and the alignment of pre-existing magnetic structures by the preceding shock may explain the observed results. In addition, we consider the existence of longitudinally extended and possibly geoeffective magnetic field fluctuations within ICME sheaths, the full understanding of which requires further multi-spacecraft analysis.

How to cite: Ala-Lahti, M., Ruohotie, J., Good, S., Kilpua, E., and Lugaz, N.: Spatial coherence of interplanetary coronal mass ejection-driven sheaths at 1 AU, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13474,, 2020.

EGU2020-10717 | Displays | ST1.2

Geomagnetic Response to a Chain of Interplanetary Coronal Mass Ejections

Mojtaba Akhavan-Tafti, Dominique Fontaine, Olivier Le Contel, and James Slavin

The most geoeffective storms in the Space Age have been driven solely by the sheath preceding an interplanetary coronal mass ejection (ICME) or by a combination of the sheath and an ICME magnetic cloud. In the present study, the magnetospheric response to a chain of three independent and well-spaced ICMEs (Pdyn > 15 nPa and Sym-H < -50 nT) spanning one month (December 12, 2015 – January 12, 2016) is investigated using WIND, Cluster, and MMS fields and plasma measurements. The first of the three ICMEs consists of a sheath preceding an ICME (ICME-SH). The latter two ICMEs are preceded by a combination of the sheath and an ICME magnetic cloud (ICME-SH-MC).

Following the passage of the first ICMEs (ICME-SH) the interplanetary environment was made up of moderate Alfvenic Mach number (MA ~ 10) and average magnetopause standoff distance (RMP ~ 11 RE). The arrival of the ICME-SH-MC then initiated a sudden storm commencement (SSC) phase. During the SSC, the storm index (Sym-H ~ +50 nT) remained positive through the ICME shock and sheath regions. The storm index and the Alfvenic Mach number sharply declined (Sym-H~ -200 nT and MA ~ 1.0, respectively) with the arrival of the leading edge of the magnetic cloud (BIMF, core ~ 20 nT) and the associated sharp IMF Bz reversal (Bz<0). The Alfvenic Mach number and IMF Bz are found to directly correlate with the Sym-H index. ICME-SH-MC compressed the magnetopause standoff distance (∂RMP/∂t ~ -1 RE/min), resulting in a sudden reduction in the total magnetospheric volume (∂VMP/∂t ~ -3×102 RE3/min), as determined by cross-scale observations. In particular, the sharp drops in the magnetospheric volume (relative change in volume >30%) with the arrival of each of the three independent ICMEs are shown to start with the SSC and remain low through the main phase, before slowly recovering (∂VMP/∂t ~ +1 RE3/min) to the pre-ICME conditions during the recovery phase.

How to cite: Akhavan-Tafti, M., Fontaine, D., Le Contel, O., and Slavin, J.: Geomagnetic Response to a Chain of Interplanetary Coronal Mass Ejections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10717,, 2020.

EGU2020-11070 | Displays | ST1.2

The Effect of Variable Solar Wind Conditions on the Bow Shock Structure and its Ability to Generate Energetic Ions

Harald Kucharek, Matthew Young, Noe Lugaz, Charles Farrugia, Steven Schwartz, and Karlheinz Trattner

Turbulent fluctuations in the magnetic field and in the bulk plasma parameters of the solar wind have important effects on the propagation and evolution of energetic particles throughout the heliosphere and on the coupling of the solar wind to the Earth's magnetosphere. At the shock the solar wind kinetic energy is converted into downstream plasma heating, ion reflection and acceleration. Changes in upstream plasma conditions can result in changes in the dynamics of the shock, its structure, and the suprathermal ion population it generates. These upstream variations can be due to transients, interplanetary shocks, and other discontinuities. They can also result from nonlinear interactions, causing an intermittent energy dissipation and leading to possible currents sheet structures. A number of these events can be found in observations from STEREO (for interplanetary traveling shocks) and CLUSTER/MMS (for the Earth’s bow shock) in the magnetosheath. 

We performed 3D-hybrid simulations to study the effects of spatially confined disturbances, such as density enhancements, depletions, and current layers/sheets and studied the shock dynamics, and the energetic particle release at various distances from the bow shock. The results of these simulations are then discussed in terms of multi-spacecraft observations in the magnetosheath at various scales.  The results show that shock reformation is highly impacted by density depressions/enhancements and so is the generation of waves and suprathermal ions. Also, upstream solar wind variations can alter the shock properties considerably at the various virtual spacecraft in the simulations.

How to cite: Kucharek, H., Young, M., Lugaz, N., Farrugia, C., Schwartz, S., and Trattner, K.: The Effect of Variable Solar Wind Conditions on the Bow Shock Structure and its Ability to Generate Energetic Ions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11070,, 2020.

EGU2020-4064 | Displays | ST1.2

A critical look at studying the interplanetary drivers of the magnetospheric disturbances

Yuri Yermolaev, Irina Lodkina, Lidia Dremukhina, Michael Yermolaev, and Alexander Khokhlachev

Although the main types of solar wind (the so-called interplanetary drivers), which may contain the southward component of the interplanetary magnetic field (Bz <0) and cause disturbances in the magnetosphere, have long been known, it has only recently been discovered that different types of drivers cause a different reaction of the magnetosphere for identical field variations (Borovsky and Denton,2006, Yermolaev et al., 2013). This discovery led to a significant increase in the number of investigations studying the response of the magnetosphere-ionosphere system to various drivers. At the same time, the number of incorrect approaches in this direction of research has increased. These errors can be attributed to 4 large classes. (1) First class includes works whose authors uncritically reacted to previously published works and use incorrect results to identify types of drivers. (2) Some authors independently incorrectly identified driver types. (3) Very often, authors associate the perturbation of the magnetosphere-ionosphere system caused by a complex driver (a sequence of single drivers) with one of the drivers, ignoring the complex nature. For example, a magnetic storm is often caused by a compression region Sheath in front of an interplanetary CME (ICME), but the authors consider the ICME to be a cause of disturbance, not Sheath. (4) Finally, there is a “lost driver” of magnetospheric disturbances: some authors simply do not consider the Sheath compression region before ICME if there is no interplanetary shock (IS) before Sheath, although this type of driver, “Sheath without IS”, generates about 10% of moderate and strong geomagnetic storms (Yermolaev et al., 2017, 2020). These errors lead to numerous mistakes and incorrect conclusions.
The work is supported by the RFFI grant 19-02-00177а. 

Borovsky, J. E., and M. H. Denton (2006), Differences between CME‐driven storms and CIR‐driven storms, J. Geophys. Res., 111, A07S08, doi:10.1029/2005JA011447

Yermolaev, Y. I., N. S. Nikolaeva, I. G. Lodkina, and M. Y. Yermolaev (2012), Geoeffectiveness and efficiency of CIR, sheath, and ICME in generation of magnetic storms, J. Geophys. Res., 117, A00L07, doi:10.1029/2011JA017139

Yermolaev, Y.I., Lodkina, I.G., Nikolaeva, N.S. et al. (2017), Some problems of identifying types of large-scale solar wind and their role in the physics of the magnetosphere, Cosmic Res. 55: 178.

Yermolaev, Y.I., Lodkina, I.G., et al. (2020), Some problems of identifying types of large-scale solar wind and their role in the physics of the magnetosphere. 4. Lost driver, Cosmic Res. 59, in press


How to cite: Yermolaev, Y., Lodkina, I., Dremukhina, L., Yermolaev, M., and Khokhlachev, A.: A critical look at studying the interplanetary drivers of the magnetospheric disturbances , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4064,, 2020.

Understanding the evolution of interplanetary coronal mass ejections (ICMEs) as they propagate through the heliosphere is essential in forecasting space weather severity. Much of our knowledge of ICMEs has been gained using in-situ measurements from single spacecraft, although the increasing number of missions in the inner heliosphere has led to an increase in multi-spacecraft studies improving our understanding of the global structure of ICMEs. Whilst most such recent studies have focused on the inner heliosphere within 1 AU, Juno cruise phase data provides a new opportunity to study ICME evolution over greater distances. We present analysis of ICMEs observed in-situ both by Juno and at least one other spacecraft within 1 AU to investigate their evolution as they propagate through the heliosphere. Investigation of the sheath region and timing considerations between spacecraft allows for the general shape of the shock front to be reconstructed. Combining in-situ observations and results of flux rope fitting techniques determines the global picture of the ICME as it propagates. However, effects on in-situ observations due to radial evolution and due to the longitudinal separation between multi-spacecraft remain hard to separate. We note the importance of the interplanetary environment in which the ICME propagates and the need for caution in radial alignment studies.  

How to cite: Davies, E., Forsyth, R., and Good, S.: Using In-Situ Juno Observations to Understand the Evolution of Interplanetary Coronal Mass Ejections Within 1 AU and Beyond , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13767,, 2020.

EGU2020-17957 | Displays | ST1.2

BepiColombo and Solar Orbiter coordinated observations: scientific cases and measurements opportunities

Lina Hadid, Melinda Dosa, Madar Akos, Tommaso Alberti, Johannes Benkhoff, Zsofia Bebesi, Lea Griton, George C. Ho, Kazumasa Iwai, Miho Janvier, Anna Milillo, Yoshizumi Miyoshi, Daniel Mueller, Go Murukami, Jim M. Raines, Daikou Shiota, Andrew Walsh, Joe Zender, and Yannis Zouganelis

BepiColombo and Solar Orbiter are two spacecraft that will be both travelling in the inner heliosphere for 5 years, between the launch of Solar Orbiter (planned in February 2020) and the end of the cruise phase of BepiColombo (2018 - 2025). Both BepiColombo (ESA/JAXA) and Solar Orbiter (ESA/NASA) are carrying exceptional and complementary plasma instrumental payloads and magnetometers. Besides, the remote-sensing instruments on board of Solar Orbiter will provide invaluable information on the state of the Sun, and therefore some contextual information for BepiColombo observations. During the five years to come, BepiColombo will evolve between the Earth and the orbit of Mercury, while Solar Orbiter’s highly elliptical orbit will cover distances from 1.02 AU to 0.28 AU.  We present here the scientific cases, modelling tools, measurement opportunities and related instruments operations that have been identified in the frame of potential coordinated observations campaign between the spacecraft.

How to cite: Hadid, L., Dosa, M., Akos, M., Alberti, T., Benkhoff, J., Bebesi, Z., Griton, L., C. Ho, G., Iwai, K., Janvier, M., Milillo, A., Miyoshi, Y., Mueller, D., Murukami, G., M. Raines, J., Shiota, D., Walsh, A., Zender, J., and Zouganelis, Y.: BepiColombo and Solar Orbiter coordinated observations: scientific cases and measurements opportunities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17957,, 2020.

EGU2020-7892 | Displays | ST1.2

Forecasting the Dst index from L5 in-situ data using PREDSTORM: accuracy and applicability

Rachel Bailey, Christian Moestl, Martin Reiss, Andreas Weiss, Ute Amerstorfer, Tanja Amerstorfer, Juergen Hinterreiter, and Maike Bauer

STEREO-B and STEREO-A are both important proxies for potential solar wind monitors at the Sun-Earth L5 point. In this study, measurements from STEREO-B are used to determine how well the Dst index in particular can be predicted using data measured near the L5 point. This is useful for determining the geoeffectivity of storms resulting from high-speed solar wind streams. Observed solar wind speeds are first mapped to the near-Earth environment as if they had been measured at L1, and the Dst is predicted from the data using a solar wind-to-Dst model. We find that Dst predicted from L5 data performs better than a recurrence model assuming the solar wind conditions repeat every 27 days, although not as well as when predicted from L1 data. The newly developed approach is currently implemented in the PREDSTORM software package to provide a real-time Dst forecast using STEREO-A data.

How to cite: Bailey, R., Moestl, C., Reiss, M., Weiss, A., Amerstorfer, U., Amerstorfer, T., Hinterreiter, J., and Bauer, M.: Forecasting the Dst index from L5 in-situ data using PREDSTORM: accuracy and applicability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7892,, 2020.

EGU2020-2446 | Displays | ST1.2

Using Ghost Fronts to Predict the Arrival Time of CMEs during 13-17 June 2012

Yutian Chi, Chris Scott, Chenglong Shen, and Yuming Wang
Coronal mass ejections (CME) are large-scale eruptions of magnetized plasma and huge energy through the corona and out into interplanetary space.
A mount of CMEs observed by HI-1 cameras present two fronts that are similar in shape but separated by a few degrees in elongation. Scott et al. (2019) interpret the ghost fronts as projections of separate discrete sections of the physical boundary of the  CME. Ghost fronts could provide information about the longitudinal shape of CME in the field of view of Hi- 1, which can be used to improve the forecast of the arrival time of ICME. During 13-15 June 2012, STEREO/SECCHI recorded two successive launched Earth-directed CMEs. Both of the two CMEs show clearly two fronts in HI-1 images. We use the ghost fronts to predict the arrival time of the two CMEs and utility the in-situ measurements from VEX and Wind to verify the accuracy of the prediction of ghost fronts model. 

How to cite: Chi, Y., Scott, C., Shen, C., and Wang, Y.: Using Ghost Fronts to Predict the Arrival Time of CMEs during 13-17 June 2012, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2446,, 2020.

EGU2020-6750 | Displays | ST1.2

Observations and results from the High-Energy Particle Detector (HEPD) on-board CSES-01 satellite

Matteo Martucci and the CSES-Limadou Collaboration

The China Seismo-Electromagnetic Satellite (CSES-01) is a mission developed by

the Chinese National Space Administration (CNSA) together with the Italian Space Agency (ASI), to investigate the near-Earth electromagnetic, plasma and particle environment. In addition, it has been designed to detect a wide number of disturbances of the ionosphere/magnetosphere transition region.

One of the main instruments on-board CSES-01 is the High Energy Particle Detector (HEPD); it is an advanced detector, completely designed and built in Italy, based on a tower of 16 scintillators and a silicon tracker that provides good energy resolution and a wide angular acceptance for electrons/positrons (3–100 MeV), protons (30–200 MeV) and light nuclei up to Oxygen.

The very good capabilities in particle detection and separation make the detector extremely well suited for Space Weather purposes;  being also able to continuously monitor the magnetospheric environment with high stability in time, HEPD can detect small variations related to transient phenomena taking place on the Sun and propagating through the solar wind.
After two years of data-taking, HEPD showed impressive capabilities in measuring the various particle distributions along its orbit, starting from sub-cutoff protons/electrons, up to galactic cosmic ray particles at higher latitudes. The former class includes both stably-trapped particles in the Radiation Belts and particles bounced back from the top of the atmosphere without being able to escape the magnetic trap (re-entrant albedo). For cosmic ray particles, precise measurements of their spectra are needed to understand the acceleration and subsequent propagation of low-energy particles in the inner sector of the heliosphere and, more general, in our Galaxy.

We report precision measurements of the protons in the >30 MeV energy region and electrons in the >5 MeV energy range, performed by HEPD in a un-disturbed heliosphere during a low solar activity period (2018/2020).

How to cite: Martucci, M. and the CSES-Limadou Collaboration: Observations and results from the High-Energy Particle Detector (HEPD) on-board CSES-01 satellite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6750,, 2020.

ST1.3 – Exploring the near-Sun environment – Results from the first orbits of Parker Solar Probe and preparation for Solar Orbiter

EGU2020-22164 * | Displays | ST1.3 | Highlight

Solar Orbiter: Europe's mission to the Sun

Yannis Zouganelis, Daniel Mueller, Chris St Cyr, Holly Gilbert, and Teresa Nieves-Chinchilla

ESA’s Solar Orbiter mission is scheduled for launch in February 2020, and will focus on exploring the linkage between the Sun and the heliosphere. It is a collaborative mission with NASA that will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere, and the origin and acceleration of solar wind plasma. By approaching as close as 0.28 AU, Solar Orbiter will view the Sun with high spatial resolution and combine this with in-situ measurements of the surrounding heliosphere. Over the course of the mission, the highly elliptical orbit will get progressively more inclined to the ecliptic plane. Thanks to this new perspective, Solar Orbiter will deliver images and comprehensive data of the unexplored Sun’s polar regions and the side of the Sun not visible from Earth. This talk will provide a mission overview, highlight synergies with NASA’s Parker Solar Probe and summarise current status.

How to cite: Zouganelis, Y., Mueller, D., St Cyr, C., Gilbert, H., and Nieves-Chinchilla, T.: Solar Orbiter: Europe's mission to the Sun, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22164,, 2020.

EGU2020-17904 | Displays | ST1.3 | Highlight

The SO/PHI instrument on Solar Orbiter and its data products

Sami K. Solanki, Johann Hirzberger, Thomas Wiegelmann, Achim Gandorfer, Joachim Woch, and José Carlos del Toro Iniesta

A central instrument of Solar Orbiter is the Polarimetric and Helioseismic Imager, SO/PHI. It is a vector magnetograph that also provides data for helioseismology. SO/PHI is composed of two telescopes, a full-disk telescope (FDT) and a high-resolution telescope (HRT). The HRT will observe at a resolution as high as 200 km on the solar surface, while the FDT will obtain the magnetic field and velocity of the full solar disc whenever it observes. SO/PHI will be the first solar spectro-polarimeter to leave the Sun-Earth line, opening up some unique perspectives, such as the first detailed view of the solar poles. This will allow not just a more precise and exact mapping of the polar magnetic field than possible so far, but will also enable us to follow the dynamics of individual magnetic features at high latitudes and to determine solar surface and sub-surface flows right up to the poles. In addition to its standard data products (vector magnetograms, continuum images and maps of the line-of-sight velocity), SO/PHI will also provide higher-level data products. These will include synoptic charts, local magnetic field extrapolations starting from HRT data and global magnetic field extrapolations (from FDT data) with potential field source-surface (PFSS) models and possibly also non-potential models such as NLFFF (non-linear force-free fields), magnetostatics and MHD. The SO/PHI data products will usefully complement the data taken by other instruments on Solar Orbiter and on Solar Probe, as well as instruments on the ground or in Earth orbit. Combining with observations by Earth-based and near-Earth telescopes will enable new types of investigations, such as stereoscopic polarimetry and stereoscopic helioseismology.

How to cite: Solanki, S. K., Hirzberger, J., Wiegelmann, T., Gandorfer, A., Woch, J., and del Toro Iniesta, J. C.: The SO/PHI instrument on Solar Orbiter and its data products , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17904,, 2020.

EGU2020-5800 | Displays | ST1.3 | Highlight

The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter : Capabilities, Performance and First results.

Milan Maksimovic, Jan Souček, Stuart D. Bale, Xavier Bonnin, Thomas Chust, Yuri Khotyaintsev, Matthieu Kretzschmar, Dirk Plettemeier, Manfred Steller, and Štěpán Štverák

We will review the instrumental capabilities of the Radio and Plasma Waves (RPW) Instrument on Solar Orbiter which at the time of writing this abstract is planned for a launch on February 5th 2020. This instrument is designed to measure in-situ magnetic and electric fields and waves from 'DC' to a few hundreds of kHz. RPW will also observe solar radio emissions up to 16 MHz. The RPW instrument is of primary importance to the Solar Orbiter mission and science requirements, since it is essential to answer three of the four mission overarching science objectives. In addition, RPW will exchange on-board data with the other in-situ instruments, in order to process algorithms for interplanetary shocks and type III Langmuir waves detections. If everything goes well after the launch, we will hopefully be able to present the first RPW data and results gathered during the commissioning.

How to cite: Maksimovic, M., Souček, J., Bale, S. D., Bonnin, X., Chust, T., Khotyaintsev, Y., Kretzschmar, M., Plettemeier, D., Steller, M., and Štverák, Š.: The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter : Capabilities, Performance and First results., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5800,, 2020.

EGU2020-22044 | Displays | ST1.3

Energetic Particles in the Inner Heliosphere: Solar Orbiter

Robert F. Wimmer-Schweingruber, Javier Rodriguez-Pacheco, Stephan Böttcher, Ignacio Cernuda, Nina Dresing, Wolfgang Dröge, Sandra Eldrum, Francisco Espinose Lara, Raul Gomez-Herrero, Bernd Heber, George Ho, Andreas Klassen, Alexander Kollhoff, Shrinivasrao Kulkarni, Gottfried Mann, César Martin, Glenn Mason, Daniel Pacheco, Manuel Prieto, and Sebastian Sanchez and the Robert F. Wimmer-Schweingruber

To be measured as energetic particles in the heliosphere ions and electrons must undergo three processes: injection, acceleration, and transport. Suprathermal seed particles have speeds well above the fast magnetosonic speed in the solar wind frame of reference and can vary from location to location and within the solar activity cycle. Acceleration sites include reconnecting current sheets in solar flares or magnetospheric boundaries, shocks in the solar corona, heliosphere and a planetary obstacles, as well as planetary magnetospheres. Once accelerated, particles are transported from the acceleration site into and throughout the heliosphere. Thus, by investigating properties of energetic particles such as their composition, energy spectra, pitch-angle distribution, etc. one can attempt to distinguish their origin or injection and acceleration site. This in turn allows us to better understand transport effects whose underlying microphysics is also a key ingredient in the acceleration of particles.

In this presentation we will present some clear examples which link energetic particles from their observing site to their source locations. These include Jupiter electrons, singly-charged He ions from CIRs, and 3He from solar flares. We will compare these examples with the measurement capabilities of the Energetic Particle Detector (EPD) on Solar Orbiter and consider implications for the key science goal of Solar Orbiter and Solar Proble Plus – How the Sun creates and controls the heliosphere.

How to cite: Wimmer-Schweingruber, R. F., Rodriguez-Pacheco, J., Böttcher, S., Cernuda, I., Dresing, N., Dröge, W., Eldrum, S., Espinose Lara, F., Gomez-Herrero, R., Heber, B., Ho, G., Klassen, A., Kollhoff, A., Kulkarni, S., Mann, G., Martin, C., Mason, G., Pacheco, D., Prieto, M., and Sanchez, S. and the Robert F. Wimmer-Schweingruber: Energetic Particles in the Inner Heliosphere: Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22044,, 2020.

EGU2020-19143 | Displays | ST1.3

First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances

Matthieu Kretschmar, Volodya Krasnoselskikh, Jean-Yves Brochot, Guillaume Jannet, Thierry Dudok de Wit, Clara Froment, Milan Maksimovic, Thomas Chust, Olivier Le Contel, Jan Soucek, and David Pisa

The Search Coil Magnetometer (SCM) onboard Solar Orbiter is part of the Radio and Plasma Waves (RPW) experiment and measures the variations of the magnetic field between 10 Hz and 50 kHz on three axes and between 1 kHz and 1MHz in one axis. The SCM is located on the boom of the spacecraft and its signal is processed by the LFR, TDS, and HFR analyzers of the RPW experiment. These measurements are essential for the characterization of waves and turbulence in the solar wind. We will describe the first observations made by the instrument with an emphasis on its performances. 

How to cite: Kretschmar, M., Krasnoselskikh, V., Brochot, J.-Y., Jannet, G., Dudok de Wit, T., Froment, C., Maksimovic, M., Chust, T., Le Contel, O., Soucek, J., and Pisa, D.: First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19143,, 2020.

EGU2020-20154 | Displays | ST1.3

Relative abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter

Natalia Zambrana Prado, Eric Buchlin, and Hardi Peter

With the launches of Parker Solar Probe and Solar Orbiter, we are closer than ever to linking solar activity on the surface and in the corona to the inner heliosphere. In this quest, relative abundance measurements will be key as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect.

Comparing in-situ and remote sensing composition data, coupled with modeling, will allow us to trace back the source of heliospheric plasma. Solar Orbiter has a unique combination of in-situ and remote sensing instruments that will hopefully allow us to make such comparisons.

High telemetry will not always be available with SPICE (SPectral Imaging of the Coronal Environment), the EUV spectrometer on board Solar Orbiter. We have therefore developed a method for measuring relative abundances that is both telemetry efficient and reliable. Unlike methods based on Differential Emission Measure (DEM) inversion, the Linear Combination Ratio (LCR) method does not require a large number of spectral lines. This new method is based on optimized linear combinations of only a few UV spectral lines. We present some abundance diagnostics applied to synthesized radiances of spectral lines observable by SPICE.

How to cite: Zambrana Prado, N., Buchlin, E., and Peter, H.: Relative abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20154,, 2020.

EGU2020-4720 | Displays | ST1.3

The Proton and Alpha Sensor (PAS) of Solar Orbiter Mission: design, operation, scientific return simulation, and first flight results

Philippe Louarn, andrei fedorov, and Christopher Owen and the SWA/PAS team

Solar Orbiter is an ESA/NASA mission that will provide an unprecedented opportunity to discover the fundamental connections between the rapidly varying solar atmosphere and the solar wind. The Solar Wind Analyzer (SWA) plasma package shall provide comprehensive in-situ measurements of the solar wind. In particular, the Proton-Alpha Sensor (PAS) will determine the properties of the dominant solar wind ion population through the measurement of the 3D distribution function, density, bulk velocity, temperature, and heat fluxes, at temporal cadences ranging form 4 s to ~0.1 s. The closest approach of Solar Orbiter to the Sun is 0.28 AU. At this distance the solar wind Vow, solar UV, and solar infrared fluxes increase by a factor 13 compared to near-Earth space. The PAS instrument will provide high cadence 3D distribution function measurements (up to 13 per second) all the way from closest approach to 1 AU. This paper give a basic information about PAS design, and describes the PAS measurement scheme adopted for varying solar wind conditions and our approach to the fast sampling of 3D distribution functions. We also provide a simulations of the expected scientific return. If possible, a first glance of PAS commissioning results will be presented.

How to cite: Louarn, P., fedorov, A., and Owen, C. and the SWA/PAS team: The Proton and Alpha Sensor (PAS) of Solar Orbiter Mission: design, operation, scientific return simulation, and first flight results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4720,, 2020.

EGU2020-19314 | Displays | ST1.3 | Highlight

Plasma and magnetic field dynamics in the young solar wind

Justin Kasper and the On behalf of the SWEAP Investigation science team

Parker Solar Probe (PSP) has completed four encounters with the Sun since launch, three with a perihelion of 35.7 solar radii and one at 27.9 solar radii in January of this year.  More than a factor of two closer to the Sun than any previous mission, observations by the spacecraft are already revealing a surprisingly dynamic and non-thermal solar wind plasma near the Sun.  An overview of initial findings related to the solar wind and coronal plasmas will be presented, including the discovery of large-amplitude velocity spikes, highly non-thermal distribution functions, and large non-radial flows of plasma near the Sun observed by the Solar Wind Electrons Alphas and Protons (SWEAP) Investigation plasma instruments and the FIELDS Investigation electromagnetic field instruments.  Once PSP dropped below a quarter of the distance from the Sun to the Earth, SWEAP began to detect a persistent and growing rotational circulation of the plasma around the Sun peaking at 40-50 km/s at perihelion as the Alfvén mach number fell to 3.  This finding may support theories for enhanced stellar angular momentum loss due to rigid coronal rotation, but the circulation is large, and angular momentum does not appear to be conserved, suggesting that torques still act on the young wind at these distances.  PSP also measured numerous intense and organized Alfvénic velocity spikes with strong propagating field reversals and large jumps in speed.  These field reversals and jets call for an overhaul in our understanding of the turbulent fluctuations that may, by energizing the solar wind, hold the key to its origin.

How to cite: Kasper, J. and the On behalf of the SWEAP Investigation science team: Plasma and magnetic field dynamics in the young solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19314,, 2020.

EGU2020-19398 | Displays | ST1.3 | Highlight

The Dust Environment in the Inner Heliosphere

Russell Howard, Guillermo Stenborg, David Malaspina, Jamey Szalay, and Petr Pokorny

The Parker Solar Probe (PSP) mission has completed 4 encounters through the solar corona significantly closer to the Sun than previous measurements. While PSP does not have a dedicated dust detector, measurements by the various instruments can provide insights into the dust environment in the inner heliosphere.  Throughout the PSP orbit, interplanetary dust is impacting the spacecraft.  Three-dimensional reconstructions of FIELDS observations show that the rate and direction of the dust impacts varies throughout the PSP orbit.  During the encounter WISPR also finds the rate of impacts changes through the encounter period, but also a decrease in the intensity of the light scattered by the dust particles.  The smooth decrease in the WISPR intensity beginning at about 0.1 AU is consistent with the production of Beta-meteroids seen by FIELDS. In this presentation, we will discuss the observations from the FIELDS and WISPR instruments and discuss initial models of the dust environment.  The authors acknowledge support from the NASA Parker Solar Probe program.

How to cite: Howard, R., Stenborg, G., Malaspina, D., Szalay, J., and Pokorny, P.: The Dust Environment in the Inner Heliosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19398,, 2020.

EGU2020-6063 * | Displays | ST1.3 | Highlight

Energetic Particle Environment near the Sun from Parker Solar Probe

Nathan Schwadron and the PSP-ISʘIS Group

NASA’s Parker Solar Probe (PSP) mission recently plunged through the inner heliosphere to perihelia at ~24 million km (~35 solar radii), much closer to the Sun than any prior human made object. Onboard PSP, the Integrated Science Investigation of the Sun (ISʘIS) instrument suite made groundbreaking measurements of solar energetic particles (SEPs). Here we discuss the near-Sun energetic particle radiation environment over PSP’s first two orbits, which reveal where and how energetic particles are energized and transported. We find a great variety of energetic particle events accelerated both locally and remotely. These include co-rotating interaction regions (CIRs), “impulsive” SEP events driven by acceleration near the Sun, and events related to Coronal Mass Ejections (CMEs). These ISʘIS observations made so close to the Sun provide critical information for investigating the near-Sun transport and energization of solar energetic particles that was difficult to resolve from prior observations. We discuss the physics of particle acceleration and transport in the context of various theories and models that have been developed over the past decades. This study marks a major milestone with humanity’s reconnaissance of the near-Sun environment and provides the first direct observations of the energetic particle radiation environment in the region just above the corona.

How to cite: Schwadron, N. and the PSP-ISʘIS Group: Energetic Particle Environment near the Sun from Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6063,, 2020.

EGU2020-1901 | Displays | ST1.3 | Highlight

Properties of Suprathermal-through-Energetic He Ions Associated with Stream Interaction Regions Observed over Parker Solar Probe’s First Two Orb¬¬its

Mihir Desai and the Parker Solar Probe ISOIS, FIELDS & SWEAP Team

The Integrated Science Investigation of the Sun (IS☉IS) suite on board NASA’s Parker Solar Probe (PSP) observed six distinct enhancements in the intensities of suprathermal-through-energetic (~0.03-3 MeV nucleon-1) He ions associated with corotating or stream interaction regions during its first two orbits. Our results from a survey of the time-histories of the He intensities, spectral slopes, and anisotropies, and the event-averaged energy spectra during these events show: 1) In the two strongest enhancements, seen at 0.35 au and 0.85 au, the higher energy ions arrive and maximize later than those at lower energies. In the event seen at 0.35 au, the He ions arrive when PSP was away from the SIR trailing edge and entered the rarefaction region in the high-speed stream; 2) The He intensities are either isotropic or show sunward anisotropies in the spacecraft frame; and 3) In all events, the energy spectra between ~0.2–1 MeV nucleon-1are power-laws of the form ∝E-2. In the two strongest events, the energy spectra are well represented by flat power-laws between ~0.03–0.4 MeV nucleon-1modulated by exponential roll-overs between ~0.4–3 MeV nucleon-1. We conclude that the SIR-associated He ions originate from sources or shocks beyond PSP’s location rather than from acceleration processes occurring atnearby portions of local compression regions. Our results also suggest that rarefaction regions that typically follow the SIRs facilitate easier particle transport throughout the inner heliosphere such that low energy ions do not undergo significant energy loss due to adiabatic deceleration, contrary to predictions of existing models.

How to cite: Desai, M. and the Parker Solar Probe ISOIS, FIELDS & SWEAP Team: Properties of Suprathermal-through-Energetic He Ions Associated with Stream Interaction Regions Observed over Parker Solar Probe’s First Two Orb¬¬its, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1901,, 2020.

EGU2020-11550 | Displays | ST1.3

The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere

Christopher Chen and the PSP FIELDS and SWEAP Teams

The first two orbits of the Parker Solar Probe (PSP) spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 Rs). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include: increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of -3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfvenic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfven speed. The energy flux in this turbulence at 0.17 au was found to be ~10% of that in the bulk solar wind kinetic energy, becoming ~40% when extrapolated to the Alfven point, and both the fraction and rate of increase of this flux towards the Sun is consistent with turbulence-driven models in which the solar wind is powered by this flux.

How to cite: Chen, C. and the PSP FIELDS and SWEAP Teams: The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11550,, 2020.

EGU2020-22182 | Displays | ST1.3

Analysis of the Internal structure of the Streamer Blow Out Observed by the Parker Solar Probe during the First Solar Encounter

Teresa Nieves-Chinchilla, Adam Szabo, Kelly E. Korreck, Nathalia Alzate, Laura A. Balmaceda, Benoit Lavraud, Kristoff Paulson, Ayris A. Narock, Samantha Wallace, Lan K. Jian, Janet G. Luhman, Huw Morgan, Aleida Higginson, and Charles N. Arge and the PSP team

We present an analysis of the internal structure of a coronal mass ejection (CME) detected by in situ instruments onboard the Parker Solar Probe (PSP) spacecraft during its first solar encounter. On 2018 November 11 at 23:53 UT, the FIELDS magnetometer measured an increase in strength of the magnetic field as well as a coherent change in the field direction. The SWEAP instrument simultaneously detected the low proton temperature and signatures of bi-directionality in the electron pitch angle distribution (PAD). These signatures are indicative of a CME embedded in the slow solar wind. In conjunction with PSP was the STEREO A spacecraft, which enabled the remote observation of a streamer blow-out by the SECCHI suite of instruments. The source at the Sun of the slow and well-structured flux-rope was identified in an overlying streamer.

Our detailed inspection of the internal transient structure magnetic properties suggests high complexity in deviations from an ideal flux rope 3D topology. Reconstructions of the magnetic field conguration reveal a highly distorted structure consistent with the highly elongated `bubble' observed remotely. A double-ring substructure observed in the SECCHI-COR2 eld of view (FOV) is suggestive of a double internal flux rope. Furthermore, we describe a scenario in which mixed topology of a closed flux rope is combined with the magnetically open structure, which helps explain the flux dropout observed in the measurements of the electron PAD. Our justication for this is the plethora of structures observed by the EUV imager (SECCHI-EUVI) in the hours preceding the streamer blowout evacuation. Finally, taking advantage of the unique observations from PSP, we explore the first stages of the effects of coupling with the solar wind and the evolutionary processes in the magnetic structure. We found evidence of bifurcated current sheets in the structure boundaries suggestive of magnetic reconnection. Our analysis of the internal force imbalance indicates that internal Lorentz forces continue to dominate the evolution of the structure in the COR2 FOV and serves as the main driver of the internal flux rope distortion as detected in situ at PSP solar distance.

How to cite: Nieves-Chinchilla, T., Szabo, A., Korreck, K. E., Alzate, N., Balmaceda, L. A., Lavraud, B., Paulson, K., Narock, A. A., Wallace, S., Jian, L. K., Luhman, J. G., Morgan, H., Higginson, A., and Arge, C. N. and the PSP team: Analysis of the Internal structure of the Streamer Blow Out Observed by the Parker Solar Probe during the First Solar Encounter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22182,, 2020.

EGU2020-11552 | Displays | ST1.3

The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe

Nicolas Poirier, Athanasios Kouloumvakos, Alexis P. Rouillard, Rui Pinto, Angelos Vourlidas, Guillermo Stenborg, Emeline Valette, Russell A. Howard, Phillip Hess, Arnaud Thernisien, Nathan Rich, Léa Griton, Mikel Indurain, Nour-Edine Raouafi, Michael Lavarra, and Victor Réville

The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 Rsun when Parker Solar Probe (PSP) was located inside 0.25 AU during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 AU. To analyze and interpret WISPR observations which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using full WISPR dataset from the first encounter. From the exploitation of this map and also from sequential WISPR images we show the presence of multiple sub-structures inside streamers and pseudo-streamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3-D magneto-hydrodynamic (MHD) models and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion towards the individual coronal structures we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 AU. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189.

How to cite: Poirier, N., Kouloumvakos, A., Rouillard, A. P., Pinto, R., Vourlidas, A., Stenborg, G., Valette, E., Howard, R. A., Hess, P., Thernisien, A., Rich, N., Griton, L., Indurain, M., Raouafi, N.-E., Lavarra, M., and Réville, V.: The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11552,, 2020.

The relative helium abundance (AHe) and alpha-proton relative drift often serve as one of the solar wind source identifiers. However, observations at 1 AU suggest that these relative properties may be affected by the interaction of different solar wind streams. Since the influence of stream interaction is reduced near the Sun, a comparison of observations at 1 AU and close to the Sun could help to reveal the processes which lead to AHe variations. In-situ measurements near the Sun are provided by the SWEAP instrument onboard Parker Solar Probe. It consists of electrostatic analyzers (SPANs) and the Faraday cup (SPC). SPAN-Ai measures the 3-D ion distribution from the shadowed region behind the spacecraft thermal shield and is equipped with a mass-to-charge detection. SPC is directed to the Sun and provides fast measurements of the ion reduced distribution function (RDF) as a function of energy/charge. We develop a new data analysis technique for computations of the proton and helium parameters from the RDFs measured by SPC and compare it with SPAN observations. Then, we combine the PSP measurements with observations at 1 AU and focus on variations of the helium properties. Finally, we discuss the connection between AHe variations and changes of the solar wind source region.

How to cite: Durovcova, T. and the PSP: Comparison of properties of the solar wind helium component close to the Sun and at 1 AU, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2750,, 2020.

EGU2020-4911 | Displays | ST1.3

GEANT 4 Simulation of the Helios E6 - Proton Contamination of Relativistic Electron Measurements

Malte Hörlöck, Bernd Heber, and Johannes Marquardt

The Helios mission consisted of two almost identical spacecraft in highly elliptic orbits launched in 1974 (Helios A) and 1976 (Helios B). Until Parker Solar Probes first perihelion, Helios B was the first spacecraft to reach a distance of 0.29 AU to the Sun. One of its instruments is the Experiment 6 (E6) which was designed and built at the Christian-Albrechts-University Kiel in order to measure ions (protons up to iron) in the energy range of 1.3 MeV/nucleon up to several GeV/nucleon and electrons in the energy range from 0.3 to about 8 MeV. The instrument relies on the dE/dx-E and on the dE/dx-Cherenkov method for stopping and penetrating particles, respectively. Electrons are separated from ions by the signal in the first 100 µm thick solid state detector. Any particle that does not trigger this detector is identified as an electron. Since the solid state detectors are not working perfectly, a significant part of protons is identified as electrons. Here, we present a new method to correct the electron measurements for the cross talk based on detailed instrument simulations.

How to cite: Hörlöck, M., Heber, B., and Marquardt, J.: GEANT 4 Simulation of the Helios E6 - Proton Contamination of Relativistic Electron Measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4911,, 2020.

EGU2020-14874 | Displays | ST1.3

Initial in-flight performance results from Solar Orbiter RPW/BIAS

Yuri V. Khotyaintsev, Andris Vaivads, Daniel B. Graham, Niklas J. T. Edberg, Erik P. G. Johansson, Milan Maksimovic, Stuart D. Bale, Thomas Chust, Matthieu Kretzschmar, and Jan Soucek

The BIAS subsystem is a part of the Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission. It allows sending bias current to each of the three RPW antennas. By setting the appropriate bias current the antenna potential can be shifted closer to the local plasma potential. This allows us to measure the floating potential of the spacecraft, as well as the electric field in the DC/LF frequency range with higher accuracy and lower noise level. Here we present the very initial results on RPW/BIAS in-flight performance based on the operations during the instrument commissioning.

How to cite: Khotyaintsev, Y. V., Vaivads, A., Graham, D. B., Edberg, N. J. T., Johansson, E. P. G., Maksimovic, M., Bale, S. D., Chust, T., Kretzschmar, M., and Soucek, J.: Initial in-flight performance results from Solar Orbiter RPW/BIAS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14874,, 2020.

EGU2020-18183 | Displays | ST1.3

Electromagnetic radiation from upper-hybrid wave turbulence driven by electron beams in solar plasmas

Gaetan Gauthier, Catherine Krafft, and Philippe Savoini

Solar radio bursts of Type III are believed to result from a sequence of physical processes ultimately leading to electromagnetic wave emissions near the electron plasma frequency ωp and its harmonic 2ωp. The radiation bursts are due to energetic electron beams accelerated during solar flares. When propagating in the solar corona and the interplanetary wind, these fluxes excite Langmuir and upper-hybrid wave turbulence, which can be further transformed into electromagnetic radiation near the frequencies ωp and 2ωp.

It is believed that, in a homogeneous plasma, Langmuir turbulence evolves due to three-wave interaction processes, such as the fusion of Langmuir waves L with sound waves S leading to the formation of electromagnetic waves Tωp at ωp or the decay of L-waves into S-waves and Tωp-waves. On the other hand, the electromagnetic waves radiated at 2ωp should arise from the coalescence L + L’ --> Tp of Langmuir waves L generated by the beam with Langmuir waves L’ coming from the electrostatic decay L --> L’ +  S.

Large-scale 2D3V Particle-In-Cell simulations have been performed with the fully kinetic code Smilei [Derouillat et al., 2018], using parameters typical of Type III solar radio busts. The excitation of upper-hybrid wave turbulence by energetic electron beams propagating in magnetized plasmas leads ultimately to electromagnetic emissions near the fundamental and the harmonic plasma frequencies.

Derouillat et al. , Comput. Phys. Commun., 222, 351, 2017.

How to cite: Gauthier, G., Krafft, C., and Savoini, P.: Electromagnetic radiation from upper-hybrid wave turbulence driven by electron beams in solar plasmas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18183,, 2020.

EGU2020-18573 | Displays | ST1.3

Large-scale electron solar wind parameters of the inner heliosphere with Parker Solar Probe/FIELDS

Karine Issautier, Mingzhe Liu, Michel Moncuquet, Nicole Meyer-Vernet, Milan Maksimovic, Stuart Bale, and Marc Pulupa

We present in situ properties of electron density and temperature in the inner heliosphere obtained during the three first solar encounters at 35 solar radii of the Parker Solar Probe mission. These preliminary results, recently shown by Moncuquet et al., ApJS, 2020, are obtained from the analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the radio RFS/FIELDS instrument along the trajectories extending between 0.5 and 0.17 UA from the Sun, revealing different states of the emerging solar wind, five months apart. The temperature of the weakly collisional core population varies radially with a power law index of about -0.8, much slower than adiabatic, whereas the temperature of the supra-thermal population exhibits a much flatter radial variation, as expected from its nearly collisionless state. These measured temperatures are close to extrapolations towards the Sun of Helios measurements.

We also present a statistical study from these in situ electron solar wind parameters, deduced by QTN spectroscopy, and compare the data to other onboard measurements. In addition, we focus on the large-scale solar wind properties. In particular, from the invariance of the energy flux, a direct relation between the solar wind speed and its density can be deduced, as we have already obtained based on Wind continuous in situ measurements (Le Chat et al., Solar Phys., 2012). We study this anti-correlation during the three first solar encounters of PSP.

How to cite: Issautier, K., Liu, M., Moncuquet, M., Meyer-Vernet, N., Maksimovic, M., Bale, S., and Pulupa, M.: Large-scale electron solar wind parameters of the inner heliosphere with Parker Solar Probe/FIELDS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18573,, 2020.

EGU2020-18888 | Displays | ST1.3

The RPW Time Domain Sampler (TDS) on Solar Orbiter: In-flight performance and first data

Jan Soucek, Ludek Uhlir, Radek Lan, David Pisa, Ivana Kolmasova, Ondrej Santolik, Vratislav Krupar, Oksana Kruparova, Milan Maksimovic, Matthieu Kretzschmar, Yuri Khotyaintsev, and Thomas Chust

The Radio and Plasma Wave instrument (RPW) for Solar Orbiter includes a Time Domain Sampler sub-unit (TDS) designed to capture electromagnetic waveform measurements of high-frequency plasma waves and antenna voltage spikes associated with dust impacts. TDS will digitize three components of the electric field and one magnetic component at 524 kHz sampling rate and scan the obtained signal for plasma waves and dust impact signatures. The main science target of TDS are Langmuir waves observed in the solar wind in association with Type II and Type III solar bursts, interplanetary shocks, magnetic holes, and other phenomena. In this poster, we present the scientific data products provided by the TDS instrument and discuss the first data obtained during the commissioning phase. The first data will be used to evaluate the actual performance of the RPW TDS instrument.

How to cite: Soucek, J., Uhlir, L., Lan, R., Pisa, D., Kolmasova, I., Santolik, O., Krupar, V., Kruparova, O., Maksimovic, M., Kretzschmar, M., Khotyaintsev, Y., and Chust, T.: The RPW Time Domain Sampler (TDS) on Solar Orbiter: In-flight performance and first data , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18888,, 2020.

EGU2020-21075 | Displays | ST1.3

Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe

Robert Allen, George Ho, Lan Jian, David Lario, Dusan Odstrcil, Charles Arge, Sam Badman, Stuart Bale, Anthony Case, Eric Christian, Christina Cohen, Carl Henney, Matthew Hill, Shaela Jones, Justin Kasper, Kelly Korreck, David Malaspina, David McComas, Nour Raouafi, and Michael Stevens

The first four orbits of Parker Solar Probe (PSP) consists of many observations of stream interaction regions (SIRs), which form when fast solar wind streams overtake slower solar wind. While it is known that SIRs accelerate ions in the heliosphere and can trigger geomagnetic storms, the temporal and radial evolution of SIRs is still an active topic of research. During the first four orbits of PSP, SIRs were observed by PSP at small heliospheric distances, as well as at 1 au by the Advanced Composition Explorer (ACE), Wind, and Solar Terrestrial Relations Observatory (STEREO) missions. These SIRs are observed not only at different heliospheric distances, but also at different points in the temporal development of the stream interface. Through analyzing the various SIRs together, insight can be gained in regards to the spatial and temporal evolution of SIR characteristics, as well as to the mechanisms of particle acceleration and transport along the SIR interface. The general characteristics of SIRs observed by PSP during the first four orbits are presented, and an in-depth comparison of a few of the SIR events is conducted to further analyze the evolution of SIR streams in the inner heliosphere. These observations show examples of a fast solar wind stream steepening into an SIR, with evidence of locally accelerated particles via compressive mechanisms at the interface distinguishable from observations of particles likely accelerated at shocks formed at larger heliospheric distances.

How to cite: Allen, R., Ho, G., Jian, L., Lario, D., Odstrcil, D., Arge, C., Badman, S., Bale, S., Case, A., Christian, E., Cohen, C., Henney, C., Hill, M., Jones, S., Kasper, J., Korreck, K., Malaspina, D., McComas, D., Raouafi, N., and Stevens, M.: Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21075,, 2020.

EGU2020-21407 | Displays | ST1.3

Seeing Helios electron data through the eyes of Solar Orbiter: modelling the angular response of EPD/EPT and its application to the full inversion of Helios events

Daniel Pacheco, Angels Aran, Raul Gomez-Herrero, Neus Agueda, David Lario, Bernd Heber, Blai Sanahuja, Nicolas Wijsen, and Robert F. Wimmer-Schweingruber

The pitch-angle distribution of electron intensities is an essential piece of information in order to understand the transport processes undergone by the particles in their journey from their acceleration sites to the spacecraft and, to infer properties of the particle sources such as their intensity and duration.

In a previous work, we modelled fifteen solar relativistic electron events observed at different heliocentric radial distances by the Helios spacecraft (Pacheco et al. 2019). We used a Monte-Carlo transport model and an inversion procedure to fit the in-situ observations, and inferred both the electron mean free path in the interplanetary space and the injection histories of the electrons at two solar radii from the Sun. We applied a full inversion procedure, that is, we considered both the angular and the energetic responses of the Helios/E6 particle experiment in the modelling of the electron events.

By using the same methodology as previously employed for ACE/EPAM, STEREO/SEPT and Helios/E6 instruments, we have modelled the angular response of the Electron Proton Telescope (EPT) of the Energetic Particle Detector (EPD) on board Solar Orbiter. Here, we present the study of the modelled angular response and its application to several of the solar energetic particle (SEP) events previously modelled as if Solar Orbiter were located at the Helios position. We compare the pitch-angle distributions measured by Solar Orbiter and Helios at different phases of the intensity-time profile of the SEP events, that is, near the particle onset, peak and on the decay of the event, and for different interplanetary magnetic field orientations provided by the Helios measurements.

We found that despite Helios were spinning spacecraft which gathered electron information from eight angular sectors, the four Solar Orbiter/EPD/EPT fields of view will often offer similar angular coverage. We also found that, under specific circumstances, EPT can obtain better pitch angle distribution information than Helios, specifically when the interplanetary magnetic field points away from the ecliptic.

We expect, then, that Solar Orbiter will provide us with numerous and valuable observations that will permit us to untangle the transport effects that electrons, protons and ions suffer in their journey through interplanetary space.

How to cite: Pacheco, D., Aran, A., Gomez-Herrero, R., Agueda, N., Lario, D., Heber, B., Sanahuja, B., Wijsen, N., and Wimmer-Schweingruber, R. F.: Seeing Helios electron data through the eyes of Solar Orbiter: modelling the angular response of EPD/EPT and its application to the full inversion of Helios events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21407,, 2020.

EGU2020-22532 | Displays | ST1.3

High resolution multi-viewpoint observations of CME kinematics and dynamics

Niclas Mrotzek and Volker Bothmer

Coronal mass ejections (CMEs) are impulsive outbursts of coronal plasma bound in magnetic structures. Their initiation and evolution into the heliosphere covers several orders of magnitude of temporal and spatial scales that can be observed with space-borne extreme ultraviolet imagers, coronagraphs and heliospheric imagers. In this work we present a systematic investigation of the early dynamics of CMEs including their kinematics, orientation and geometrical evolution. For this purpose, a dedicated set of 21 Earth-directed CMEs between July 2011 and November 2012 was selected and analyzed. The CME parametrization is obtained by applying a 3D modelling method, the Graduated Cylindrical Shell (GCS) model, to simultaneous multi-viewpoint observations taken with the SECCHI instrument suite onboard the twin STEREO spacecraft and with the LASCO coronagraphs onboard the SOHO satellite. By using these instruments, the CME dynamics including the kinematics and geometry, are covered in high detail over a wide spatial range. For the majority of events it started in the field of view of EUVI below 2 solar radii and extended into the field of view of HI1 up to 100 solar radii. The results reveal interactions of the CMEs with the ambient solar wind. CME deflections of up to 31° in longitude and 18° in latitude were measured within the first 30 solar radii. Furthermore, evidence of CME oscillations with periods between 29 and 93 minutes were found. The analysis provides important implications for more reliable space weather forecasts and further analysis through the new observations from Parker Solar Probe and Solar Orbiter.


How to cite: Mrotzek, N. and Bothmer, V.: High resolution multi-viewpoint observations of CME kinematics and dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22532,, 2020.

EGU2020-8398 | Displays | ST1.3

Modelling coronal mass ejection flux ropes signatures using Approximate Bayesian Computation: applications to Parker Solar Probe

Andreas Weiss, Christian Möstl, Teresa Nieves-Chinchilla, Tanja Amerstorfer, Erika Palmerio, Martin Reiss, Rachel Bailey, Jürgen Hinterreiter, Ute Amerstorfer, and Maike Bauer

We present an updated three-dimensional coronal rope ejection (3DCORE) model and an associated pipeline that is capable of producing extremely large ensembles of synthetic in-situ magnetic field measurements from simulated coronal mass ejection flux ropes. The model assumes an empirically motivated torus-like flux rope structure that expands self-similarly and contains an embedded analytical magnetic field. Using an Approximate Bayesian computation (ABC) algorithm we validate the model by showing that it is capable of qualitatively reproducing measured flux rope signatures. The ABC algorithm also gives us uncertainty estimates in the form of probability distributions for all model parameters. We show the first results for applying our model and algorithms to coronal mass ejections observed in situ by Parker Solar Probe, specifically the event on 2018 November 12 at 0.26AU, where we attempt to reproduce the measured magnetic field signatures and furthermore reconstruct the global flux rope geometry.

How to cite: Weiss, A., Möstl, C., Nieves-Chinchilla, T., Amerstorfer, T., Palmerio, E., Reiss, M., Bailey, R., Hinterreiter, J., Amerstorfer, U., and Bauer, M.: Modelling coronal mass ejection flux ropes signatures using Approximate Bayesian Computation: applications to Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8398,, 2020.

EGU2020-11111 | Displays | ST1.3

Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe

Jonathan Niehof and Nathan Schwadron and the PSP/IS☉IS team

A series of solar energetic particle (SEP) events were observed at Parker Solar Probe (PSP) by the Integrated Science Investigation of the Sun (IS☉IS) during the period from April 18, 2019 through April 24, 2019. The PSP spacecraft was located near 0.48 au from the Sun on Parker spiral field lines that projected out to 1 au within ∼25° of near Earth spacecraft. These SEP events, though small compared to historically large SEP events, were amongst the largest observed thus far in the PSP mission and provide critical information about the space environment inside 1 au during SEP events. During this period the Sun released multiple coronal mass ejections (CMEs). One of these CMEs observed was initiated on April 20, 2019 at 01:25 UTC, and the interplanetary CME (ICME) propagated out and passed over the PSP spacecraft. Observations by the Electromagnetic Fields Investigation (FIELDS) show that the magnetic field structure was mostly radial throughout the passage of the compression region and the plasma that followed, indicating that PSP did not directly observe a flux rope internal to the ICME, consistent with the location of PSP on the flank of the ICME. Analysis using relativistic electrons observed near Earth by the Electron, Proton and Alpha Monitor (EPAM) on the Advanced Composition Explorer (ACE) demonstrates the presence of flare-accelerated seed populations during the events observed. The energy spectrum of the IS☉IS observed seed population below 1 MeV is consistent with the superposition of acceleration processes near the limit of plasma stability. IS☉IS observations reveal the compression and acceleration of seed populations during the passage of the ICME, which is likely a key part of the pre-acceleration process that occurs close to the Sun and pre-conditions the energetic particle acceleration process.

How to cite: Niehof, J. and Schwadron, N. and the PSP/IS☉IS team: Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11111,, 2020.

EGU2020-17554 | Displays | ST1.3

Determination of Solar Energetic Particle anisotropies based on four-sector measurements - Study based on STEREO/SEPT in preperation of SolO/EPT

Maximilian Bruedern, Nina Dresing, Bernd Heber, Lars Berger, Alexander Kollhoff, and Patrick Kühl

With the launch of Solar Orbiter (SolO) Solar Energetic Particles (SEPs) can be observed at a radial distance of 0.284 to 0.9 AU and an inclination out of the ecliptic up to 34 degree. The properties of SEP observations carry information about their source at the Sun as well as their transport through the interplanetary medium. Their energy is mostly determined close to the Sun. As SEPs propagate outward along the Interplanetary Magnetic Field (IMF) the pitch-angle with respect to the local field is systematically focused due to the radially decreasing IMF. However, stochastic changes are induced by scattering at fluctuations of the IMF. Often the first order anisotropy of SEPs is calculated to disentangle imprints of source and transport. Strong anisotropies indicate periods of weak pitch-angle scattering. Although many modeling and observational studies are based on the anisotropy, its uncertainty is often neglected which could result in inaccurate conclusions. Therefore, we propose a new method based on a bootstrap approach where we consider (1) directional instrument responses, (2) the variation of the magnetic field, and (3) the stochastic nature of detection. Here, we present our procedure and final results for different SEP events using measured data of the IMF and particle fluxes by the Solar Electron and Proton Telescope (SEPT) on board of each STEREO spacecraft. The SEPT provides four viewing directions with a view cone of 0.66 sr each on a three axis stabilized spacecraft. In contrast the Electron and Proton Telescope (EPT) on board SolO also consists of four viewing directions but each telescope has a much smaller view cone of 0.21 sr. Due to the very similar instrument setup we can apply our method both to the SEPT and EPT.

How to cite: Bruedern, M., Dresing, N., Heber, B., Berger, L., Kollhoff, A., and Kühl, P.: Determination of Solar Energetic Particle anisotropies based on four-sector measurements - Study based on STEREO/SEPT in preperation of SolO/EPT, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17554,, 2020.

EGU2020-18502 | Displays | ST1.3

Radial Evolution of Inverted Heliospheric Magnetic Field Between 0.3 and 1 AU

Allan Macneil, Mathew Owens, Robert Wicks, Mike Lockwood, Matthew Lang, and Sarah Bentley

Local inversions, or ‘switchbacks’, in the heliospheric magnetic field (HMF) have recently been identified as prominent features in the inner heliosphere through observations by Parker Solar Probe. These inversions coincide with spikes in radial velocity, and have been interpreted as possibly being the result of jets originating in the corona. While magnetic inversions with similar properties to these jets have also been observed by Helios around its perihelion of ~0.3 AU, inversions with a range of properties and scales have long been studied at distances of 1 AU and beyond. The processes which form the inversions seen outside of 0.3 AU, and whether they are a result of solar wind formation in the solar corona or the transport of solar wind through the heliosphere, are not clear. We present a statistical study on the occurrence of inverted heliospheric magnetic field using Helios 1 observations spanning heliocentric distances 0.3—1 AU. The evolution of inversion occurrence allows us to identify probable locations in the heliosphere where inversions may be produced. Based on these results, we make suggestions as to which processes are most likely responsible for inverted HMF observed between 0.3 and 1 AU.

How to cite: Macneil, A., Owens, M., Wicks, R., Lockwood, M., Lang, M., and Bentley, S.: Radial Evolution of Inverted Heliospheric Magnetic Field Between 0.3 and 1 AU, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18502,, 2020.

EGU2020-20181 | Displays | ST1.3

Acceleration of particles in different parts of erupting coronal mass ejections

Valentina Zharkova, Qian Xia, Joel Dahlin, and Spiro Antiochos

We examine particle energisation in CMEs generated via the breakout mechanism and explore both 2D and 3D MHD configurations. In the breakout scenario, reconnection at a breakout current sheet (CS) initiates the flux rope eruption by destabilizing the quasi-static force balance. Reconnection at the flare CS triggers the fast acceleration of the CME, which forms flare loops below and triggers particle acceleration in flares. We present test-particle studies that focus on two selected times during the impulsive and decay phases of the eruption and obtain particle energy gains and spatial distributions. We find that particles accelerated more efficiently in the flare CS than in the breakout CS even in the presence of large magnetic islands. The maximum particle energy gain is estimated from the energization terms based on the guiding-center approximation. Particles are first accelerated in the CSs (with or without magnetic islands) where Fermi-type acceleration dominates. Accelerated particles escape to the interplanetary space along open field lines rather than trapped in flux ropes, precipitate into the chromosphere along the flare loops, or become trapped in the flare loop top due to the magnetic mirror structure. Some trapped particles are re-accelerated, either via re-injection to the flare CS or through a local betatron-type acceleration associated with compression of the magnetic field. The energy gains of particles result in relatively hard energy spectra during the impulsive phase. During the gradual phase, the relaxation of the shear in magnetic field reduces the guiding magnetic field in the flare CS, which leads to a decrease in particle energization efficiency.

How to cite: Zharkova, V., Xia, Q., Dahlin, J., and Antiochos, S.: Acceleration of particles in different parts of erupting coronal mass ejections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20181,, 2020.

EGU2020-5027 | Displays | ST1.3

Energy spectra of carbon and oxygen - Predictions from HELIOS E6 for Solar Orbiter HET

Johannes Marquardt, Bernd Heber, Robert Elftmann, and Robert Wimmer-Schweingruber

Anomalous cosmic rays (ACRs) are well-suited to probe the transport conditions of energetic particles in the innermost heliosphere. We revisit the HELIOS Experiment 6 (E6) data in view of the upcoming Solar Orbiter Energetic Particle Detector (EPD) suite that will perform measurements during a comparable solar minimum within the same distance.

Adapting the HELIOS energy ranges for oxygen and carbon to the ones given by the High Energy Telescope (HET) allows us to determine predictions for the upcoming measurements but also to put constraints on particle transport models that provide new insight into the boundary conditions close to the Sun.

We present here the adapted energy spectra of galactic cosmic ray (GCR) carbon and oxygen, as well as of ACR oxygen during solar quiet time periods between 1975 to 1977. Due to the higher energy threshold of HET in comparison to E6 gradients of about 20% at 15 MeV/nucleon are expected. The largest ACR gradient measured by E6 was obtained to be about 75% between 9 and 13 MeV/nucleon and 0.4 AU and 1 AU.

How to cite: Marquardt, J., Heber, B., Elftmann, R., and Wimmer-Schweingruber, R.: Energy spectra of carbon and oxygen - Predictions from HELIOS E6 for Solar Orbiter HET , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5027,, 2020.

A new method to calculate semi-analytically the radiation efficiency of electromagnetic waves emitted at specific frequencies by electrostatic wave turbulence in solar plasmas with random density fluctuations is presented. It is applied to the case of electromagnetic emissions radiated at the fundamental plasma frequency ωp by beam-driven Langmuir wave turbulence during Type III solar bursts. It is supposed that the main radiation mechanism is the linear conversion of electrostatic to electromagnetic waves on the background plasma density fluctuations, at constant frequency. Due to the presence of such inhomogeneities, the rates of electromagnetic radiation are modified compared to the case of uniform plasmas. Results show that the radiation efficiency of Langmuir wave turbulence into electromagnetic emissions at ωp is nearly constant asymptotically, the electromagnetic energy density growing linearly with time, and is proportional to the average level of density fluctuations. Comparisons with another analytical method developed by the authors and with space observations are satisfactory.

How to cite: Krafft, C. and Volokitin, A.: Efficiency of electromagnetic emission by electrostatic turbulence in solar plasmas with density inhomogeneities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21572,, 2020.

EGU2020-7595 | Displays | ST1.3

Type III Radio Bursts and Langmuir Wave Excitation

Gottfried Mann, Christian Vocks, Mario Bisi, Eoin Carley, Bartosz Dabrowski, Richard Fallows, Peter Gallagher, Andrzej Krankowski, Jasmina Magdalenic, Christophe Marque, Diana Morosan, Hanna Rothkaehl, and Pietro Zucca

Type III radio bursts are a common phenomenon the Sun’s nonthermal radio radiation. They appear as stripes of enhanced radio emission with a rapid drift from high to low frequencies in dynamic radio spectra. They are considered as the radio signatures of beams of energetic electrons travelling along magnetic field lines from the solar corona into the interplanetary space. With the ground based radio interferometer LOFAR and the instrument FIELDS onboard NASA’s “Parker Solar Probe” (PSP) , type III radio bursts can be observed simultaneously from high (10-240 MHz) to low frequencies (0.01-20 MHz) with LOFAR and PSP’s FIELDs, respectively. That allows to track these electron beams from the corona up to the interplanetary space. Assuming that a population of energetic electrons is initially injected, the velocity distribution function of these electrons evolves into a beam like one. Such distribution function leads to the excitation of Langmuir waves which convert into radio waves finally observed as type II radio bursts. Numerical calculations of the electron-beam-plasma interaction reveal that the Langmuir waves are excited by different parts of the energetic electrons at different distances in the corona and interplanetary space. This result is compared with special type III radio bursts observed with LOFAR and PSP’s FIELDS.

How to cite: Mann, G., Vocks, C., Bisi, M., Carley, E., Dabrowski, B., Fallows, R., Gallagher, P., Krankowski, A., Magdalenic, J., Marque, C., Morosan, D., Rothkaehl, H., and Zucca, P.: Type III Radio Bursts and Langmuir Wave Excitation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7595,, 2020.

EGU2020-20919 | Displays | ST1.3

Energetic and Suprathermal Particle Composition Measurements from Solar Orbiter

George Ho, Glenn Mason, Robert Wimmer-Schweingruber, and Javier Rodríguez-Pacheco

Particles that have energies of a few times the solar wind plasma energy up to 100s of keV/q are called suprathermal particles. Recent studies have revealed that these particles play a significant role as seed particles for further acceleration to higher energies.  This may occur either close to the Sun in solar energetic particle (SEP) events, but also locally at 1 AU in energetic storm particle events, or even outside 1 AU as ions accelerated in Corotating Interaction Regions. The constituents of this suprathermal ion reservoir are therefore expected to vary in time and space. The composition and spectra of these ions provide us the telltale of their origin and acceleration mechanism.  It is therefore important to make high time resolution measurements of the composition and spectra of this particle population in the inner heliosphere to better characterize its origins and role as a seed population in particle acceleration processes. Because of the vastly different mass-per-charge ratios of the various possible origins of suprathermal ions, we expect to see distinct difference and radial dependencies in their abundances in low-energy accelerated particles in the inner heliosphere.  Here we describe the measurements that we will be making on Solar Orbiter that will make significant contributions to the understanding of the particle population in this largely unexplored energy range.

How to cite: Ho, G., Mason, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Energetic and Suprathermal Particle Composition Measurements from Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20919,, 2020.

EGU2020-10050 | Displays | ST1.3

The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion

Thomas Chust, Olivier Le Contel, Matthieu Berthomier, Alessandro Retinò, Fouad Sahraoui, Alexis Jeandet, Paul Leroy, Jean-Christophe Pellion, Véronique Bouzid, Bruno Katra, Rodrigue Piberne, Yuri Khotyaintsev, Andris Vaivads, Volodya Krasnoselskikh, Matthieu Kretzschmar, Jan Souček, Ondrej Santolík, Milan Maksimovic, and Stuart D. Bale and the MMS team

Solar Orbiter (SO) is an ESA/NASA mission for exploring the Sun-Heliosphere connection which has been launched in February 2020. The Low Frequency Receiver (LFR) is one of the main subsystems of the Radio and Plasma Wave (RPW) experiment on SO. It is designed for characterizing the low frequency (~0.1Hz–10kHz) electromagnetic fields & waves which develop, propagate, interact, and dissipate in the solar wind plasma. In correlation with particle observations it will help to understand the heating and acceleration processes at work during its expansion. We will present the first LFR data gathered during the Near Earth Commissioning Phase, and will compare them with MMS data recorded in similar solar wind condition.

How to cite: Chust, T., Le Contel, O., Berthomier, M., Retinò, A., Sahraoui, F., Jeandet, A., Leroy, P., Pellion, J.-C., Bouzid, V., Katra, B., Piberne, R., Khotyaintsev, Y., Vaivads, A., Krasnoselskikh, V., Kretzschmar, M., Souček, J., Santolík, O., Maksimovic, M., and Bale, S. D. and the MMS team: The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10050,, 2020.

EGU2020-20293 | Displays | ST1.3

Localized magnetic field structures and their boundaries in the near-Sun solar wind from Parker Solar Probe measurements

Vladimir Krasnoselskikh and the PSP Magnetic Structures

One of the most striking discoveries made by Parker Solar Probe during its first three encounters with the Sun is the presence of a multitude of relatively small-scale structures that stand out as sudden deflections of the magnetic. They were named “switchbacks” since some of them show up the full reversal of the radial component of the magnetic field and return to “regular” solar wind conditions. We carried out an analysis of three typical switchback structures having slightly different characteristics: I. Alfv´enic structures, where the variations of the magnetic field components take place conserving the magnitude of the magnetic field constant; II. Compressional, where the magnetic field magnitude varies together with changes of the components of the magnetic field; III. Structures manifesting full reversal of the magnetic field, they may be presumably similar to Alfv´enic, but they are some extremal class of “switchback structures”. We analyzed the properties of the magnetic field of these structures and the characteristics of their boundaries. Our observations and analysis lead to the conclusion that the structures represent localized magnetic field tubes moving with respect to surrounding plasma. The very important characteristic of these tubes consists of the existence of a relatively narrow boundary layer on the surface of the tube that accommodates flowing currents. These currents supposedly closed on the surface of the structure, and typically they have comparable azimuthal and the tube axes aligned components. These currents are supported by the presence of the effective electric field ensured by quite strong gradients of the density, and ion plasma pressure. The ion beta is typically larger than one inside the structure, and less than one outside. Another important feature is an electromagnetic wave accommodated on the surface of the structure. Its role consists in assistance to particles in carrying currents, to electrons parallel to magnetic field, and perpendicular to field to ions.

How to cite: Krasnoselskikh, V. and the PSP Magnetic Structures: Localized magnetic field structures and their boundaries in the near-Sun solar wind from Parker Solar Probe measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20293,, 2020.

ST1.6 – Exploration of the Heliosphere and the Interstellar Medium with IMAP and Interstellar Probe

EGU2020-3981 | Displays | ST1.6 | Highlight

Interstellar Heliosphere Probes (IHPs)

Qiugang Zong

Supersonic solar wind streams away from the Sun in all directions, interaction with the local interstellar medium to form a giant plasma bubble, which is coined by A. J. Dessler as “heliosphere”. Voyager 1& 2 spacecraft have recently encountered the heliospheric boundaries of this plasma bubble, e.g. the termination shock, heliosheath and heliopause.

To explore further on the dynamics on the heliospheric boundaries, even the hydrogen wall, and the local interstellar medium,  an Interstellar Heliosphere Probes (IHPs)mission have been proposed to Chinese national space agency (two spacecraft, one towards the nose of the heliopause, one opposite). The plan is that the spacecraft is to reach 100AU when it is 100th anniversary of the PR China (2049). Thus, IHP will allow us to discover, explore, and understand fundamental astrophysical processes in the largest plasma laboratory-- the heliosphere.

How to cite: Zong, Q.: Interstellar Heliosphere Probes (IHPs), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3981,, 2020.

EGU2020-6119 | Displays | ST1.6 | Highlight

Interstellar Probe: The Next Step

Ralph McNutt, Mike Gruntman, Stamatios Krimigis, Edmond Roelof, Pontus Brandt, Kathleen Mandt, Steven Vernon, Michael Paul, and Robert Stough

An “Interstellar Probe” to the nearby interstellar medium has been discussed in the scientific community for almost 60 years. The key concept has always been to depart from the Sun outward “as fast as possible.” Scientific goals have principally focused on heliospheric topics throughout multiple studies, with potential “bonus science” in both astrophysics and planetary science. The passages of Voyagers 1 and 2 into that medium have only raised multiple new questions, rather than “solving” the outstanding question of the interaction of the solar wind with the nearby interstellar medium. In particular, solar activity apparently continues to have an effect on nearby interstellar space, magnetic field changes in crossing from the heliosheath into the local medium are only in magnitude and not direction, and the three-dimensional structure of the energetic neutral atom (ENA) “ribbon” remains unknown. The power levels on the Voyagers continue to decrease toward the operational floor which is likely to be reached within the next five years, limiting the extent of our exploration, and ending heliophysics deep-space measurements beyond the asteroid belt for the indefinite future. The salient question for a dedicated mission is “What can the Interstellar Probe do that no other mission can do?” The answer requires an in-depth look at current capabilities for such a mission, e.g., solar system escape speed, data downlink bandwidth, and mission lifetime with science topics, technological readiness of mission and instrument concepts, and realistic mission costs. To provide technical input to the upcoming Solar and Space Physics Decadal Survey, NASA has contracted with the Johns Hopkins University Applied Physics Laboratory (APL) to execute a “First Pragmatic Interstellar Probe Mission Study.” The effort focuses on near-term engineering readiness (ready for launch by 2030) but also includes input regarding compelling science and associated required measurements and instrumentation, assuming that such a mission would commence during the next Decadal time period. This is not a Science Definition Team (SDT) exercise, but rather an assessment of possibilities. In that spirit, we continue to seek input from across the international space science community regarding potential science goals, measurements, instruments, and their implementation readiness in order to help inform the engineering team in support of a concept mission. We provide a status report on this ongoing effort.

How to cite: McNutt, R., Gruntman, M., Krimigis, S., Roelof, E., Brandt, P., Mandt, K., Vernon, S., Paul, M., and Stough, R.: Interstellar Probe: The Next Step, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6119,, 2020.

 We describe the very local interstellar medium (VLISM)
immediately outside of the outer heliosphere. The VLISM consists 
of four partially ionized clouds - the Local Interstellar Cloud (LIC), 
G cloud, Blue cloud, and Aql cloud that are in contact with the outer 
heliosphere, and ionized gas produced by extreme-UV radiation 
primarily from the star Epsilon CMa. We construct the 
three-dimensional shape of the LIC based on interstellar line 
absorption along 62 sightlines and show that in the direction of 
Epsilon CMa, Beta CMa, and Sirius B the neutral hydrogen column 
density from the center of the LIC looking outward is a minimum. 
We call this region the ``hydrogen hole''. In this direction, the 
presence of Blue cloud absorption and the absence of LIC absorption 
can be simply explained by the Blue cloud lying just outside of the 
heliosphere. We propose that the outer edge of the Blue cloud is a 
Str\"omgren shell driven toward the heliosphere by high pressures in 
the H II region. The outer edges of other clouds facing Epsilon CMa 
are likely also Stromgren shells. Unlike previous models, the LIC
surrounds less than half of the heliosphere.

We find that the vectors of neutral and ionized helium flowing
through the heliosphere are inconsistent with the mean LIC flow 
vector and describe several possible explanations. The ionization
of nearby intercloud gas is consistent with photo-ionization by 
Epsilon CMa and hot white dwarfs without requiring additional 
sources of ionization or million degree plasma. In the upwind 
direction, the heliosphere is passing through an environment of 
several LISM clouds, which may explain the recent influx of 
interstellar grains containing 60Fe from supernova ejecta measured 
in Antarctica snow. The Sun will leave the outer partof the LIC 
in less than 1900 years, perhaps this year, to either enter the 
partially ionized G cloud or a highly ionized intercloud layer. 
The heliosphere will change in either scenario. An instrumented 
deep space probe sending back in situ plasma and magnetic field 
measurements from 500-1,000 AU is needed to understand the 
heliosphere environment rather than integrated data along the 
sightlines to stars.  

How to cite: Linsky, J.: What lies immediately outside of the heliosphere in the very local interstellar medium (VLISM): morphology of the Local Interstellar Cloud, its hydrogen hole, Stromgren Shells, and 60Fe accretion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1410,, 2020.

EGU2020-5547 * | Displays | ST1.6 | Highlight

Overview of the Instellar Mapping and Acceleration Probe (IMAP) Mission

David McComas

This talk provides an overview of the Interstellar Mapping and Acceleration Probe (IMAP) mission and what we hope and expect to learn from it. IMAP is currently in Phase B and is slated to launch in the fall of 2024. IMAP simultaneously investigates two of the most important, and intimately coupled, research areas in Heliophysics today: 1) the acceleration of energetic particles and 2) the interaction of the solar wind with the local interstellar medium. IMAP’s ten instruments provide a complete set of observations to simultaneously examine the particle injection and acceleration processes at 1 AU while remotely dissecting the global heliospheric interaction and its response to particle populations generated through these processes. For more information about IMAP, see: McComas, D.J., et al., Interstellar mapping and acceleration Probe (IMAP): A New NASA Mission, Space Science Review, 214:116, doi:10.1007/s11214-018-0550-1, 2018.

Open Access: 

How to cite: McComas, D.: Overview of the Instellar Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5547,, 2020.

EGU2020-18777 | Displays | ST1.6

Heliospheric Energetic Neutral Atoms: Numerical Modelling and Comparison with IBEX-Hi data

Igor Baliukin, Vladislav Izmodenov, and Dmitry Alexashov

The Interstellar Boundary Explorer (IBEX) spacecraft has been measuring fluxes of the Energetic Neutral Atoms (ENAs) using the IBEX-Hi (0.3 – 6 keV) instrument since 2008. We have developed the numerical model to calculate ENA hydrogen fluxes employing reconstruction of the trajectories of the atoms (backward in time) from 1 au, where they are observed by IBEX, to the point of their origin in the inner heliosheath, i.e. the region of the perturbed solar wind between the termination shock and the heliopause, where the plasma is strongly heated (T ~ 106 K). Along the trajectory of the atom, differential fluxes of the newly originated ENAs with a given speed are integrated, and losses due to ionization processes (charge exchange with protons and photoionization) are also taken into account.

The key factor in the simulation is a detailed consideration of the supra-thermal component of pickup ions (PUIs) that originate in the region of the supersonic solar wind and picked by the heliospheric magnetic field since this component is «parental» to the ENA. We take into account the supra-thermal component by solving the kinetic equation under the assumption that PUI distribution function is isotropic everywhere in the heliosphere. This method compares favorably with other existing approaches since it is based on fundamental physical laws.

We have calculated model maps of the ENA fluxes based on the previously developed kinetic-MHD models of the SW/LISM interaction (Izmodenov & Alexashov, 2015, 2020), and performed the comparison with IBEX-Hi data. The IBEX-Hi data is one of the few sources of knowledge about the structure of the heliospheric boundary, imposing significant limitations on the parameters of the model of the heliosphere. As a result of the comparison, we concluded that 1) ENA fluxes from the region of the inner heliosheath are extremely sensitive to the form of PUI distribution function; 2) the model of the heliosphere Izmodenov & Alexashov (2020) that differs from the model Izmodenov & Alexashov (2015) in configuration of the interstellar magnetic field reproduces the IBEX-Hi data better; 3) despite a relatively good agreement, there are some qualitative differences between the model calculations and IBEX-Hi data in some energy channels of IBEX-Hi. The reasons for these differences are discussed.

How to cite: Baliukin, I., Izmodenov, V., and Alexashov, D.: Heliospheric Energetic Neutral Atoms: Numerical Modelling and Comparison with IBEX-Hi data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18777,, 2020.

EGU2020-10815 | Displays | ST1.6

Scattering of Interstellar Neutral Atoms in the Outer Heliosheath

Pawel Swaczyna, David J. McComas, Eric J. Zirnstein, and Jacob Heerikhuisen

Interstellar neutral (ISN) atoms from the very local interstellar medium (VLISM) penetrate the heliosphere and are observed by detectors located near 1 au, e.g., on the Interstellar Boundary Explorer (IBEX), and in the future on the Interstellar Mapping and Acceleration Probe (IMAP). Interpretation of these observations provides insight into the physical conditions in the VLISM but requires modeling of the processes that change distributions of ISN atoms inside the heliosphere and beyond. Here, we focus on the consequences of collisional scattering in the outer heliosheath (OHS), beyond the heliopause. Charge exchange collisions create secondary atoms from the OHS ions, which have a different flow speed and temperature than pristine ISN atoms, especially close to the heliopause. It is widely assumed that these collisions do not change directions of interacting particle velocities. We show that this assumption is not justified for the typical collisions speed in the OHS, and therefore the distribution functions of secondary atoms are different than those calculated without this momentum exchange.  This angular scattering in charge exchange collisions results in secondary atom production terms that show elongated distributions aligned with the relative bulk speed of the parent populations, as well as higher temperatures (up to ~3000 K) and shifted bulk speeds (up to ~2 km s-1). Distributions of ISN atoms are also affected by elastic collisions that similarly show significant scattering for collision energies typical in the OHS. Eventually, these scattering processes modify distributions of ISN atom observed in the heliosphere directly and as pickup ions. These effects may help explain systematical discrepancies between the IBEX data and current models.

How to cite: Swaczyna, P., McComas, D. J., Zirnstein, E. J., and Heerikhuisen, J.: Scattering of Interstellar Neutral Atoms in the Outer Heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10815,, 2020.

EGU2020-2107 | Displays | ST1.6

Mirror instability driven by pickup ions in the outer heliosheath

Amenehsadat Mousavianzehaie, Kaijun Liu, and Kyungguk Min

Kinetic linear instability analysis and hybrid simulations are carried out to examine the role of mirror instability in scattering the pickup ions in the outer heliosheath. The dynamics of these pickup ions is essential to
the understanding of the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer
(IBEX). While most previous studies have focused on the ion cyclotron instability driven by the pickup ions,
recent work based on a simple ring velocity distribution of the pickup ions suggested that the mirror mode can
also be unstable and contribute to the scattering of the pickup ions. The present study performs linear analysis
as well as hybrid simulations for a more realistic, multi-component pickup ion velocity distribution given by the
global modeling of neutral atoms in the heliosphere. The linear theory results indicate unstable mirror modes
with considerable growth rates. The corresponding hybrid simulations further confirm that the mirror modes can
grow and aid the pitch-angle broadening of the pickup ions. So the role of mirror mode should not be ignored in
the stability study of the outer heliosheath pickup ions.

How to cite: Mousavianzehaie, A., Liu, K., and Min, K.: Mirror instability driven by pickup ions in the outer heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2107,, 2020.

Interaction between the solar wind and the local interstellar environment has been studied using several observation techniques, including in-situ sampling of the plasma, magnetic field,  energetic ions by the Voyager spacecraft; remote-sensing observations of energetic neutral atoms (IBEX, Cassini); and the primary and secondary populations of interstellar neutral gas (IBEX-Lo). Understanding the processes at the heliospheric boundary and of the conditions outside the heliosphere is typically  done by fitting parameters used in models of this interaction to various observables, including the Voyager crossing distances of the termination shock and the heliopause, the size of the IBEX ribbon and its center directions, the sky distribution of the Lyman-alpha helioglow, and the flux of interstellar gas at 1 au from direct-sampling observations. Typically, it is expected that all or most of these observables are successfully reproduced. Even though the interaction of interstellar neutral gas with the solar wind and solar EUV output is sometimes taken into account, the global heliosphere is usually simulated as a stationary structure, with the solar wind flux, density, and magnetic field variation ignored. However, solar wind is a dynamic phenomenon, which results in variations in the plasma flow both inside and outside the heliopause and in variations of the distance to the heliopause. Based on in-situ solar wind observations, dynamic pressure of the solar wind may change by a factor of 2, which may result in a heliopause distance change by 50%, counting from the lowest-pressure conditions.

Interstellar neutral atoms reaching detectors at 1 au or contributing to the helioglow observed from 1 au need very different times to travel from the interaction  region , typically located at ~1.75 of the heliopause distance to 1 au. While the primary ISN atoms take 3—4 solar cycles to travel from this region to 1 au, with a physical time spread (not an uncertainty!) of about one solar cycle, the atoms from secondary population take as much as 15 solar cycles, with a large spread of 7 solar cycles. This implies that ISN He atoms sampled by IBEX-Lo, as well as those observed as the helioglow, originate from two different and disparate epochs. While it may be expected that the interstellar conditions at a time scale of 200 years are little variable, solar wind is definitely varying, with secular changes superimposed on the solar cycle variation.

Direct-sampling observations provide information on the plasma flow in the OHS inside ~60° around the inflow direction, with well-defined regions of the OHS contributing atoms to individual pixels observed by IBEX and IMAP at different orbits. However, the information obtained is heavily averaged over time, and the epoch  imprinted on these population is very different to the epochs characteristic for in-situ observations from the Voyagers (by 50 to 170 years!)  and remote-sensing observations of the much faster-running energetic neutral atoms.

How to cite: Bzowski, M., Kubiak, M., and Heerikhuisen, J.: What epoch and space region at the heliospheric boundaries are probing IBEX and IMAP observations of interstellar neutral gas populations?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9610,, 2020.

In this presentation solar wind electrons and protons are studied which, after their passage over the solar wind termination shock, are convected downstream into the heliosheath. Due to the electric nature of this shock, downstream electrons appear highly energized with non-equilibrium,  kappa-like  distributions . When looking upon the moments of these downstream electrons and protons, it turns out as a surprise that the pressure of the electrons, compared to the protons, is larger by a factor of 2. Then it is taken into account that the pressure of kappa-distributed particles contains contributions from particles with super-luminal velocities which need to be removed from the pressure values . Even when these reductions are carried out, it is manifest that the heliosheath pressures of electrons and protons are of equal orders of magnitudes. In conclusion it is found that there is no pressure deficit in the heliosheath with respect to the ambient interstellar medium.

How to cite: Fahr, H.-J.: The pressure-relevance of suprathermal solar wind electrons for the heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-63,, 2020.

EGU2020-2187 | Displays | ST1.6

Temporal measurements of the interstellar helium focusing cone by the Magnetospheric Multiscale Mission(MMS)

Roman Gomez, Stephen Fuselier, James Burch, Joey Mukherjee, Carrie Gonzalez, Karlheinz Trattner, Michael Starkey, and Robert Strangeway

The Sun and its associated heliosphere travels through the local interstellar medium (LISM) at 26 km/s.  This results in a flow of neutral particles constantly entering the heliosphere at the same velocity.  Neutral atoms with trajectories close to the Sun, which survive its ionizing radiation environment, become gravitationally attracted to it resulting in a focusing cone, a region of enhanced neutral density, downwind of the Sun.  The increased neutral density in these regions leads to a higher density of pickup ions created by charge-exchange of the neutrals.  In near-Earth orbit, the Magnetospheric Multiscale spacecraft (4 in all) have orbital apogees on the dayside during Earth’s annual encounter with the helium focusing cone (from mid-November to mid-December).  Since launching in March of 2015, regular acquisitions with the Hot Plasma Composition Analyzers (HPCAs) have been conducted, with acquisitions from 2017 through 2019 occurring with a 29 RE apogee, ensuring long intervals in the pristine Solar Wind.   We provide measurements of the focusing cone during the declining phase of the previous solar cycle. These measurements are used to investigate the effect of solar radiation on the focusing cone.

How to cite: Gomez, R., Fuselier, S., Burch, J., Mukherjee, J., Gonzalez, C., Trattner, K., Starkey, M., and Strangeway, R.: Temporal measurements of the interstellar helium focusing cone by the Magnetospheric Multiscale Mission(MMS), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2187,, 2020.

EGU2020-18647 | Displays | ST1.6

Low energetic Interstellar hydrogen atoms in the heliosphere: Decade of IBEX observations

Olga Katushkina, Vladislav Izmodenov, and André Galli

This work is devoted to the analysis of the interstellar hydrogen fluxes measured by IBEX spacecraft from 2009 to 2018. To calculate the fluxes we use our 3D time-dependent kinetic model of the hydrogen distribution in the heliosphere that takes into account non-maxwellian behavior of the velocity distribution function of hydrogen atoms due to charge exchange with protons at the heliospheric boundary. The temporal variations of the hydrogen fluxes during the entire solar cycle are considered and analyzed by comparison of the IBEX-Lo data and the model results. During solar maximum the measured fluxes are too low, therefore we choose several years 2009-2011 and 2017-2018 when the signal-to-noise ratio is appropriate. A parametric search is performed to determine the influence of different model parameters on the full sky maps of the fluxes. It is found that solar radiation pressure is the most crucial parameter for the position of the maximum fluxes, while the heliolatitudinal variations of the charge exchange ionization rate influence the shape of the maps during solar minimum conditions. The quantitative differences between the data and the model results are demonstrated, and several possible reasons for them are discussed.

How to cite: Katushkina, O., Izmodenov, V., and Galli, A.: Low energetic Interstellar hydrogen atoms in the heliosphere: Decade of IBEX observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18647,, 2020.

Solar wind and EUV flux are dominant ionization factors for the interstellar gas inside the heliosphere. They vary in time with the solar cycle and with heliographic latitude. The modulation of the solar ionizing factors affects the fluxes of interstellar neutral (ISN) gas and energetic neutral atoms (ENAs) on their way from heliospheric boundaries to IBEX in the Earth’s vicinity. IBEX has been measuring ISN gas of hydrogen, helium, neon, and oxygen, as well as hydrogen ENAs since the beginning of the solar cycle 24. Most of the ISN gas species observed by IBEX-Lo are prone to variations in time of the in-ecliptic ionization rates. In case of H ENAs, variations of the out-of-ecliptic solar wind are significant for data interpretation.

We present a model of ionization rates based on available observations of the solar wind and the solar EUV flux. We follow methodology discussed by Sokół et al. 2019 (ApJ 872:57), however with data selection revised according to recent data releases. We focus on ionization rates for various species in and out of the ecliptic during the decade of IBEX observations. We discuss similarities and differences in the dominant ionization processes, the latitudinal modulation, and the evolution in time.

How to cite: Sokol, J. M.: Observation-based Ionization Rates during the Decade of IBEX Observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6167,, 2020.