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, https://doi.org/10.5194/egusphere-egu2020-5536, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-2069, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-17703, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-18133, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-21334, 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, https://doi.org/10.5194/egusphere-egu2020-19255, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-10225, 2020.

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 (http://www.hesperia.astro.noa.gr) 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 https://www.springer.com/de/book/9783319600505. 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, https://doi.org/10.5194/egusphere-egu2020-8298, 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, https://doi.org/10.5194/egusphere-egu2020-4293, 2020.

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 (f_s) 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 f_s 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 f_s reveals a weak positive correlation between log I₁₉₃ and log f_s , with a correlation coefficient ≈ 0.39. As a first-order approximation, the positive relationship is determined to be log I₁₉₃ = 0.62 log f_s + 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, https://doi.org/10.5194/egusphere-egu2020-1501, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-4011, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-21894, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-7374, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-13366, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-19262, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-21663, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-6043, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-2736, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-8621, 2020.

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, https://doi.org/10.5194/egusphere-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, https://doi.org/10.5194/egusphere-egu2020-11889, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-3690, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-7451, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-4009, 2020.

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 (P_dyn > 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 (M_A ~ 10) and average magnetopause standoff distance (R_MP ~ 11 R_E). 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 M_A ~ 1.0, respectively) with the arrival of the leading edge of the magnetic cloud (B_{IMF, core} ~ 20 nT) and the associated sharp IMF B_z reversal (B_z<0). The Alfvenic Mach number and IMF B_z are found to directly correlate with the Sym-H index. ICME-SH-MC compressed the magnetopause standoff distance (∂R_MP/∂t ~ -1 R_E/min), resulting in a sudden reduction in the total magnetospheric volume (∂V_MP/∂t ~ -3×10² R_E³/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 (∂V_MP/∂t ~ +1 R_E³/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, https://doi.org/10.5194/egusphere-egu2020-10717, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-11070, 2020.

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. 

References
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. https://doi.org/10.1134/S0010952517030029

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, https://doi.org/10.5194/egusphere-egu2020-4064, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-17957, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-2446, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-22164, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-17904, 2020.

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 5^th 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, https://doi.org/10.5194/egusphere-egu2020-5800, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-22044, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-19143, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-19314, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-19398, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-6063, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-22182, 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, https://doi.org/10.5194/egusphere-egu2020-2750, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-4911, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-14874, 2020.

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 ω_p and its harmonic 2ω_p. 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 ω_p and 2ω_p.

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 T_ωp at ω_p or the decay of L-waves into S-waves and T_ωp-waves. On the other hand, the electromagnetic waves radiated at 2ω_p should arise from the coalescence L + L’ --> T_2ωp 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, https://doi.org/10.5194/egusphere-egu2020-18183, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-18573, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-18888, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-21407, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-22532, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-18502, 2020.

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, https://doi.org/10.5194/egusphere-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 ω_p 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 ω_p 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, https://doi.org/10.5194/egusphere-egu2020-21572, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-7595, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-20919, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-20293, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-3981, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-6119, 2020.

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: https://link.springer.com/article/10.1007%2Fs11214-018-0550-1 

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, https://doi.org/10.5194/egusphere-egu2020-5547, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-18777, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-10815, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-2107, 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, https://doi.org/10.5194/egusphere-egu2020-63, 2020.

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, https://doi.org/10.5194/egusphere-egu2020-2187, 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, https://doi.org/10.5194/egusphere-egu2020-6167, 2020.

The recent AMS 02 measurements show that the very local interstellar spectra (VLIS) for galactic cosmic rays cannot be directly measured at the Earth below rigidities of 40-60 GV because of solar modulation. With Voyager 1and Voyager II crossing the heliopause in 2012 and 2018, in situ experimental LIS data below 100 MeV/nuc constrain computed galactic CR spectra. However, the energy spectra in between can so far only be derived by models. This gap could be narrowed by flying an instrument like the The COsmic and Solar Particle INvestigation Kiel Electron Telescope (COSPIN/KET) that measured protons and alpha-particles in the energy range from about 4 to above 2000 MeV/n and electrons in the range up to 10 GeV in distinguished energy channels. Such a telescope would consist of two parts: 1) an entrance telescope of two semiconductors comprising a silica-aerogel Cherenkov detector with a refractive index of 1.066, selecting particles with speeds v/c = b > 0.938, and 2) a calorimeter, a lead-fluoride Cherenkov detector followed by a scintillation detector measuring escaping particles.

How to cite: Heber, B., Wimmer-Schweingruber, R., Köberle, M., Kühl, P., and Böttcher, S.: KET 02: An electron and ion telescope for an interstellar mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17863, https://doi.org/10.5194/egusphere-egu2020-17863, 2020.

The PKU energetic particle instrument (EPI) is designed to make measurements of the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range of 20–400 keV and ions from 20 keV–6 MeV. The output of front detectors is taken in anti-coincidence with center detectors, to achieve the low background. The magnet telescopes also employ the well-established dE/dx vs. total energy approach to determine the nuclear charge and mass of some ion species.

How to cite: Yang, L., Wang, L., Zong, Q., Yu, X., Wang, Y., Shi, W., and Wimmer-Schweingruber, R.: PKU Energetic Particle Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2043, https://doi.org/10.5194/egusphere-egu2020-2043, 2020.

The Solar Electron and Ion Telescope (SEIT), proposed by Peking University for a L1 non-spinning spacecraft mission, is designed to provide Omni-directional investigation of Solar energetic electrons and Ions with good time, energy and angular resolution. SEIT consists of multi group two dual double-ended magnet/foil particle telescopes which cleanly separate and measure electrons in the energy range from 50–400 keV and Ions from 60–7000 keV expected to be including protons, C and O. The multi group particle telescopes can cover the Omni-directional space. Each two dual double-ended magnet/foil particle telescopes set-up refers to the detector stack with view cones in two opposite directions: one side (electron side) is consisted of a 300um and a 500um Silicon detector whose distance is only 100um to chive a high performance, the 300um Silicon is on the front and covered by a 5um thin parylene foil to leave the electron spectrum essentially unchanged but stops low energy Ions, the other side (Ions side) is consisted of a 100um and a 500um Silicon detector whose distance is only 100um to chive a high performance and the front of the telescope is surrounded by a magnet to sweep away electrons but lets ions pass. The dead layer of the detector is only 100 Å and each detector is divided into five pixels to chive a high angular resolution. The time resolution is 1s. Simulation shows that the maximum counts of the 20 pixels can reach to 2452, while the minimum energy deposition of the 20 pixels is 300 keV. We now describe the design and GEANT4 simulation of SEIT.

How to cite: Yu, X., Huang, X., Wang, L., Shi, W., Wang, Y., Fu, H., and Liu, Z.: The GEANT4 simulation of PKU Solar Electron and Ions Telescope, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6657, https://doi.org/10.5194/egusphere-egu2020-6657, 2020.

The Energetic Particle Instrument (EPI), proposed by Peking University for a L1 mission, is designed to provide the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range from 20 to 400 keV and ions from 20 keV to 6 MeV.

The magnet of semi-conductor telescopes consists of four type 677H rare earth permanent magnets and a soft iron frame. Due to the high saturation polarization and high magnetic anisotropy of the Nd₂Fe₁₄B strongly magnetic matrix phase, this system can make the magnetic field strong enough to make the electrons deflected.

A frame made of iron-cobalt alloy VACOFLUX 50 will be able to combine two pairs of magnets and cause the magnetic field to decay rapidly in the far field. In this way, the two air gaps in the system can simultaneously provide a deflecting magnetic field for a pair of anti-parallel sensor systems.

How to cite: Shi, W., Yu, X., Wang, Y., Wang, L., Huang, X., and Liu, Z.: The Deflection Magnet Design for PKU Energetic Particle Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12082, https://doi.org/10.5194/egusphere-egu2020-12082, 2020.

Substorm is the global disruptive activity in Earth’s magnetotail, including phenomena such as reconnection, plasmoid, flux rope, BBFs, energetic particle injection, and aurora etc. The ground based observations are often hard to determine the time sequences of substorm activities, while the satellite in-situ observations often cannot distinguish between temporal and spatial variations, therefore the global imaging observations are very useful in substorm studies. In this study we demonstrate the physical design of a grid-based energetic neutral atom (ENA) imager that can provide high temporal, spatial and energy resolution ENA imaging of Earth’s magnetotail. The ENA imager takes advantage of spatial Fourier modulation to the ENA fluxes to construct the ENA images, which is inspired by RHESSI. The physical design including imaging process, the charged particle reflector, and the ENA species discrimination etc. are described, along with the engineering progresses.

How to cite: Wang, Y., Zong, Q., Wang, L., Chen, H., and Zou, H.: A High Temporal, Spatial and Energy Resolution Grid-based Energetic Neutral Atom (ENA) Imager: the Physical Design, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13050, https://doi.org/10.5194/egusphere-egu2020-13050, 2020.

In the study of internal charging of dielectrics inside the spacecraft, we mainly focus on the influence of conductivity of dielectrics induced by space radiation(Radiation Induced Conductivity), and regard the relative permittivity as constant. However, during the ground testing of dielectrics, we found that the relative permittivity of dielectrics decreased after being exposed to electron beams, thus affecting the electric field and the release of charge inside dielectrics. The relative permittivity can gradually returned to the initial state when the radiation stops. In the paper, we present the experiment result and try to give explanations on the mechanism behind this phenomenon.

How to cite: Song, S., chen, H., Yu, X., and Zong, Q.: The Influence of Space Radiation on the Relative Permittivity of Dielectrics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21360, https://doi.org/10.5194/egusphere-egu2020-21360, 2020.

Ring curent is an important current system in the Earth's magnetosphere. Many charged particles, especially protons and oxygen ions, move around the Earth due to due to electromagnetic drifts, which forms the ring current. During the main phase of a magnetic storm, ring current will grow stronger while it will decay slowly during recover phase. It is thought that charge exchange is the main mechanism of ring current decay [Daglis et al., 1999]. Hereby we use charge exchange theories to calculate charge exchange lifetimes of protons and oxygen ions during recover phase of many storms. Meanwhile, data of RBSP has been used for fitting in order to get real lifetimes of  protons and oxygen ions. We compared the observed lifetimes with the theory prediction and find that  a. the two are close at high L(>4) values and low energy(<55keV) for protons, b. the two are similar in a wide energy(1~600keV) range but a relatively narrow L(different at different energies) range, c. day or night make little difference on the comparison results.

How to cite: Chen, A., Yue, C., Chen, H., and Zong, Q.: Ring current decay during storm recover phase: RBSP Observation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21672, https://doi.org/10.5194/egusphere-egu2020-21672, 2020.

Solar energetic electron events (SEEs) are one of the most common particle acceleration phenomena occurring at the Sun, and their energy spectrum likely reflects the crucial information on the acceleration. Here we present a statistical survey of the energy spectrum of 160 SEEs measured by Wind/3DP with a clear velocity dispersion at energies of ~1-200 keV from January 1995 through December 2016, utilizing a general spectrum formula proposed by Liu et al. (2000). We find that among these 160 SEEs, 144 (90%) have a power-law (or power-law-like) spectrum bending down at high energies, including 108 (67.5%) double-power-law events, 24 (15%) Ellison-Ramaty-like events and 12 (7.5%) log-parabola events, while 16 (10%) have a power-law spectrum extending to high energies. The average power-law spectral index β₁ is 2.1±0.4 for double-power-law events, 1.7±0.8 for Ellison-Ramaty-like events, and 2.8±0.11 for single-power-law events. For the 108 double-power-law events, the spectral break energy E₀ ranges from 2 keV to 165 keV, with an average of 71±79 keV, while the average spectral index β₂ at energies above E₀is 4.4±2.3. E₀ shows a positive correlation with the electron peak flux at energies above ~40 keV, while β₁ has a negative correlation with the electron peak flux at energies above ~15 keV.  

How to cite: Wang, L., Liu, Z., Fu, H., and Krucker, S.: The Energy Spectrum of Solar Energetic Electron Events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1944, https://doi.org/10.5194/egusphere-egu2020-1944, 2020.

Magnetic reconnection is a primary driver of magnetic energy release and particle acceleration processes in space and astrophysical plasmas. Solar flares are a great example where observations have suggested that a large fraction of magnetic energy is converted into nonthermal particles and radiation. One of the major unsolved problems in reconnection studies is nonthermal particle acceleration. In the past decade or two, 2D kinetic simulations have been widely used and have identified several acceleration mechanisms in reconnection. Recent 3D simulations have shown that the reconnection layer naturally generates magnetic turbulence. Here we report our recent progresses in building a macroscopic model that includes these physics for explaining particle acceleration during solar flares. We show that, for sufficient large systems, high-energy particle acceleration processes can be well described as flow compression and shear. By means of 3D kinetic simulations, we found that the self-generated turbulence is essential for the formation of power-law electron energy spectrum in non-relativistic reconnection. Based on these results, we then proceed to solve an energetic particle transport equation in a compressible reconnection layer provided by high-Lundquist-number MHD simulations. Due to the compression effect, particles are accelerated to high energies and develop power-law energy distributions. The power-law index and maximum energy are both comparable to solar flare observations. This study clarifies the nature of particle acceleration in large-scale reconnection sites and initializes a framework for studying large-scale particle acceleration during solar flares.

How to cite: Li, X. and Guo, F.: Large-scale particle acceleration during magnetic reconnection in solar flares, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1959, https://doi.org/10.5194/egusphere-egu2020-1959, 2020.

Magnetic reconnection plays a central role in highly magnetized plasma, for example, in solar corona. Release of magnetic energy due to reconnection is believed to drive such transient phenomena as solar flares, eruptions, and jets. This energy release should be associated with a decrease of the coronal magnetic field. Quantitative measurements of the evolving magnetic field strength in the corona are required to find out where exactly and with what rate this decrease takes place. The only available methodology capable of providing such measurements employs microwave imaging spectroscopy of gyrosynchrotron emission from nonthermal electrons accelerated in flares. Here, we report microwave observations of a solar flare, showing spatial and temporal changes in the coronal magnetic field at the cusp region; well below the nominal reconnection X point. The field decays at a rate of ~5 Gauss per second for 2 minutes. This fast rate of decay implies a highly enhanced, turbulent magnetic diffusivity and sufficiently strong electric field to account for the particle acceleration that produces the microwave emission. Moreover, spatially resolved maps of the nonthermal and thermal electron densities derived from the same microwave spectroscopy data set allow us to detect the very acceleration site located within the cusp region. The nonthermal number density is extremely high, while the thermal one is undetectably low in this region indicative of a bulk acceleration process exactly where the magnetic field displays the fast decay. The decrease in stored magnetic energy is sufficient to power the solar flare, including the associated eruption, particle acceleration, and plasma heating. We discuss implications of these findings for understanding particle acceleration in solar flares and in a broader space plasma context.

How to cite: Fleishman, G., Gary, D., Chen, B., Yu, S., Kuroda, N., and Nita, G.: Characterization of turbulent magnetic reconnection in solar flares with microwave imaging spectroscopy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2099, https://doi.org/10.5194/egusphere-egu2020-2099, 2020.

Fluctuations of solar wind parameters can be strongly affected by the presence of sharp boundaries between different large-scale structures. Turbulence cannot develop freely across such boundaries, just as it could in the undisturbed solar wind. It can lead the growing of fluctuation level and changes in shape and properties of turbulent cascade too. The compression regions, for example  Sheath regions before magnetic clouds, and CIR regions (the compression areas between fast solar wind from coronal holes and slow solar wind  from coronal streamers), are  typical examples of such transitions.  Here we present the analysis of turbulence spectrum changes during crossings of  Sheath and CIR regions. We use unique high time resolution plasma measurements by BMSW instrument at Spektr-R spacecraft in order to consider both MHD and kinetic scales of turbulent cascade.  We analyze the base properties of  turbulence spectra: spectral power and slopes at corresponding scales, break frequency between scales, and also shape of spectra. We began by examining of the case study crossings of the transition regions and then compared statistically the spectral properties in such regions with the same ones in the undisturbed solar wind. We have shown that spectra fall nonlinearly at kinetic scales and become steeper with growing of fluctuation level in transition regions, at the same time the slope of spectra at MHD scale remains almost Kolmogorov. Withal some interesting features can be observed in the vicinity of the break between characteristic scales during crossing of transition regions. The given results reveal the lack of energy balance between MHD and kinetic scales, and can indicate the intensification of dissipation processes and the additional plasma heating in the  transition regions. The work is supported by Russian Science Foundation grant 16-12-10062.

How to cite: Riazantseva, M., Rakhmanova, L., Zastenker, G., Yermolaev, Y., Lodkina, I., Safrankova, J., Nemecek, Z., and Prech, L.: Characteristics of turbulence in transition regions near large-scale boundaries in the solar wind., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7605, https://doi.org/10.5194/egusphere-egu2020-7605, 2020.

So far, the problem of a short-term forecast of geomagnetic storms can be considered as solved. Meanwhile, mid-term prognoses of geomagnetic storms with an advance time from 3 hours to 3 days are still unsuccessful (see  https://www.swpc.noaa.gov/sites/default/files/images/u30/Max%20Kp%20and%20GPRA.pdf).

 This fact suggests a necessity of looking for specific processes in the solar wind preceding geomagnetic storms. Knowing that magnetic cavities filled with magnetic islands and current sheets are formed in front of high-speed streams of any type (Khabarova et al., 2015, 2016, 2018; Adhikari et al., 2019), we have performed an analysis of the corresponding ULF variations in the solar wind density observed at the Earth's orbit from hours to days before the arrival of a geoeffective stream or flow. The fact of the occurrence of ULF-precursors of geomagnetic storms was noticed a long time ago (Khabarova 2007; Khabarova & Yermolaev, 2007) and related prognostic methods were recently developed (Kogai et al. 2019), while the problem of automatization of the prognosis remained unsolved.

 A new geomagnetic storm forecast method, which employs a Recurrent Neural Network (RNN) for an automatic pattern search, is proposed. An ability of self-teaching and extracting deeply hidden non-linear patterns is the main advantage of Deep Neural Networks (DNNs) with multiple layers over traditional Machine Learning methods. We show a success of the RNN method, using either the unprocessed solar wind density data or Wavelet analysis coefficients as the input parameter for a DNN to perform an automatic mid-term prognosis of geomagnetic storms.  

Adhikari, L., et al. 2019, The Role of Magnetic Reconnection–associated Processes in Local Particle Acceleration in the Solar Wind, ApJ, 873, 1, 72, https://doi.org/10.3847/1538-4357/ab05c6
Kogai T.G. et al., Pre-storm ULF variations in the solar wind density and interplanetary magnetic field as key parameters to build a mid-term prognosis of geomagnetic storms. “GRINGAUZ 100: PLASMA IN THE SOLAR SYSTEM”, IKI RAS, Moscow, June 13–15, 2018, 140-143, ISBN 978-5-00015-043-6. https://www.researchgate.net/publication/327781146_Pre-storm_ULF_variations_in_the_solar_wind_density_and_interplanetary_magnetic_field_as_key_parameters_to_build_a_mid-term_prognosis_of_geomagnetic_storms
 Khabarova O. V., et al. 2018,  Re-acceleration of energetic particles in large-scale heliospheric magnetic cavities, Proceedings of the IAU, 76-82, https://doi.org/10.1017/S1743921318000285 
Khabarova O.V., et al. Small-scale magnetic islands in the solar wind and their role in particle acceleration. II. Particle energization inside magnetically confined cavities. 2016, ApJ, 827, 122, http://iopscience.iop.org/article/10.3847/0004-637X/827/2/122
Khabarova O., et al. Small-scale magnetic islands in the solar wind and their role in particle acceleration. 1. Dynamics of magnetic islands near the heliospheric current sheet. 2015, ApJ, 808, 181, https://doi.org/10.1088/0004-637X/808/2/181

Khabarova O.V., Current Problems of Magnetic Storm Prediction and Possible Ways of Their Solving. Sun&Geosphere,  http://sg.shao.az/v2n1/SG_v2_No1_2007-pp-33-38.pdf , 2(1), 33-38, 2007

Khabarova O.V. & Yu.I.Yermolaev, Solar wind parameters' behavior before and after magnetic storms, JASTP, 70, 2-4, 2008, 384-390, http://dx.doi.org/10.1016/j.jastp.2007.08.024

How to cite: Fridman, M.: Neural network applications in geomagnetic storm prognosis based on the pre-storm occurrence of magnetic islands in the solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1848, https://doi.org/10.5194/egusphere-egu2020-1848, 2020.

High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth’s orbit.

Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and  (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids. 

We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.

How to cite: Sagitov, T. and Kislov, R.: Formation of current sheets and plasmoids within corotating/stream interaction regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2102, https://doi.org/10.5194/egusphere-egu2020-2102, 2020.

A new form of the proton force balance equation for the plasma consisting of collisionless protons and magnetized electrons is obtained. In the equation, the electric field is expressed through the magnetic field and the divergence of electron pressure tensor. The latter is reqiured for the correct determination of boundary conditions in models of current sheets to control the force balance in the models of that type. From this, a general form of the force balance equation in a one-dimensional current sheet is obtained, and effects of electron pressure anisotropy are considered. We reproduce realistic stationary configurations of current sheets using novel methods of numerical simulations and the Vlasov equation solving. 

How to cite: Mingalev, O. and Mingalev, I.: Force balance in current sheets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2210, https://doi.org/10.5194/egusphere-egu2020-2210, 2020.

Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energize particles up to several MeV/nuc. Stream-stream interactions as well as the heliospheric current sheet – stream interactions lead to formation of large magnetic cavities, bordered by strong current sheets (CSs), which in turn produce secondary CSs and dynamical small-scale magnetic islands (SMIs) of ~0.01AU or less owing to magnetic reconnection. It has been shown that particle acceleration or re-acceleration occurs via stochastic magnetic reconnection in dynamical SMIs confined inside magnetic cavities observed at 1 AU. The study links the occurrence of CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV-MeV/nuc energies at ~5.3 AU. We analyze selected samples of different plasmas observed by Ulysses during a widely discussed event, which was characterized by a series of high-speed streams of various origins that interacted beyond the Earth’s orbit in January 2005. The interactions formed complex conglomerates of merged interplanetary coronal mass ejections, stream/corotating interaction regions and magnetic cavities. We study properties of turbulence and associated structures of various scales. We confirm the importance of intermittent turbulence and magnetic reconnection in modulating solar energetic particle flux and even local particle acceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondary stochastic particle acceleration, which changes the observed energetic particle flux time-intensity profiles and increases the final energy level to which energetic particles can be accelerated in the solar wind.

How to cite: Malandraki, O., Khabarova, O., Bruno, R., Zank, G., and Li and the ISSI-405 team, G.: Current sheets, magnetic islands and associated particle acceleration in the solar wind as observed by Ulysses near the ecliptic plane, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3730, https://doi.org/10.5194/egusphere-egu2020-3730, 2020.

Jets and mass ejections are ubiquitous features of the Sun’s corona. These explosive dynamics are all believed to be driven by magnetic reconnection at two types of current sheets that form in the solar atmosphere: those that form at magnetic null points and separatrix surfaces, and those, such as the heliospheric current sheet, that form as a result of a large expansion of a bipolar magnetic field. In our breakout model, both types of current sheets are essential for the explosive release of magnetic energy. We report on the first direct observations of reconnection and island formation in a null-point current sheet associated with a large coronal jet. The topology and velocities of the islands are in excellent agreement with our numerical simulations of coronal jets. We discuss the implications of the observations and our models for understanding the energetic particles produced by these events and their release into interplanetary space, as well as the implications for observations by Solar Orbiter and the Parker Solar Probe.

This work was supported by the NASA Living With a Star Program.

How to cite: Antiochos, S., Kumar, P., Jarpen, J., and Dahlin, J.: Observations and Simulations of Reconnecting Current Sheets in the Solar Corona, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5597, https://doi.org/10.5194/egusphere-egu2020-5597, 2020.

In this study we use theoretical concepts and computational-diagnostic tools of Tsallis non-extensive statistical theory (Tsallis q-triplet: qsen, qrel, qstat), complemented by other known tools of nonlinear dynamics such as Correlation Dimension and surrogate data, Hurst exponent, Flatness coefficient, and p-modeling of multifractality, in order to describe and understand Small-scale Magnetic Islands (SMIs) structures observed in Solar Wind (SW) with a typical size of ~0.01–0.001 AU at 1 AU. Specifically, we analyze ~0.5 MeV energetic ion time-intensity and magnetic field profiles observed by the STEREO A spacecraft during a rare, widely discussed event. Our analysis clearly reveals the non-extensive character of SW space plasmas during the periods of SMIs events, as well as significant physical complex phenomena in accordance with nonlinear dynamics and complexity theory. As our analysis also shows, a non-equilibrium phase transition parallel with self-organization processes, including the reduction of dimensionality and development of long-range correlations in connection with anomalous discussion and fractional acceleration processes can be observed during SMIs events.

How to cite: Pavlos, E., Malandraki, O., Khabarova, O., Karakatsanis, L. P., Pavlos, G. P., and Livadiotis, G.: Non-Extensive Statistical Analysis of Energetic Particle Flux Enhancements Caused by the Interplanetary Coronal Mass Ejection-Heliospheric Current Sheet Interaction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8461, https://doi.org/10.5194/egusphere-egu2020-8461, 2020.

The boundaries between large-scale solar wind streams are often accompanied by sharp changes in helium abundance.  Wherein the high value of relative helium abundance is known as a sign of some large-scale solar wind structures ( for example magnetic clouds). Unlike the steady slow solar wind where the helium abundance is rather stable and equals ~5%, in magnetic clouds its value can grow significantly up to 20% and more, and at the same time helium component becomes more variable.  In this paper we analyze the small-scale variations of solar wind plasma parameters, including the helium abundance variations in different large-scale solar wind streams, especially in magnetic clouds and Sheath regions before them. We use rather long intervals of simultaneous measurements at Spektr-R (spectrometer BMSW) and Wind (spectrometer 3DP) spacecrafts.  We choose the intervals with rather high correlation  level of plasma parameters as a whole to be sure that we are deal with the same plasma stream.  The intervals associated with different large scale-solar wind structures are selected by using of our catalog ftp://ftp.iki.rssi.ru/pub/omni/catalog/. For selected intervals we examine cross-correlation function for Spektr-R and Wind measurements  to reveal the local spatial inhomogeneities by helium abundance which can be observed only at one of spacecrafts, and we determine properties of ones. Such inhomogeneities can be generate by turbulence, which is typically getting more intense in the considered disturbed intervals in the solar wind. The work is supported by Russian Science Foundation grant 16-12-10062.

How to cite: Khokhlachev, A., Riazantseva, M., Rakhmanova, L., Yermolaev, Y., Lodkina, I., and Zastenker, G.: Small-scale variations of helium abundance in different large-scale solar wind structures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9348, https://doi.org/10.5194/egusphere-egu2020-9348, 2020.

In the standard model of solar flares, a large-scale reconnection current sheet (RCS) is postulated as the central engine for powering the flare energy release and accelerating particles. However, where and how the energy release and particle acceleration occur remain unclear due to the lack of measurements for the magnetic properties of the RCS. Here we report the first measurement of spatially-resolved magnetic field and flare-accelerated relativistic electrons along a large-scale RCS in a solar flare. The measured magnetic field profile shows a local maximum where the reconnecting field lines of opposite polarities closely approach each other, known as the reconnection X point. The measurements also reveal a local minimum near the bottom of the RCS above the flare loop-top, referred to as a "magnetic bottle". This spatial structure agrees with theoretical predictions and numerical modeling results. A strong reconnection electric field of over 4000 V/m is inferred near the X point. This location, however, shows a local depletion of microwave-emitting relativistic electrons. In contrast, the relativistic electrons concentrate at or near the magnetic bottle structure, where more than 99% of them reside at each instant. Our observations suggest crucial new input to the current picture of high energy electron acceleration.

How to cite: Fleishman, G., Chen, B., Dale, G., and Nita et al., G.: Mapping magnetic field and relativistic electrons along a solar flare current sheet, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19937, https://doi.org/10.5194/egusphere-egu2020-19937, 2020.

We propose a general fitting formula of energy spectrum of suprathermal particles, J=AE^-β1[1+(E/E₀)^α]^(β1-β2)/α, where J is the particle flux (or intensity), E is the particle energy, A is the amplitude coefficient, E₀ represents the spectral break energy, α (>0) describes the sharpness of energy spectral break around E₀, and the power-law index β₁ (β₂) gives the spectral shape before (after) the break.  When α tends to infinity (zero), this spectral formula becomes a classical double-power-law (logarithmic-parabola) spectrum. When both β₂ and E₀ tend to infinity, this formula can be simplified to an Ellison-Ramaty-like equation. Under some other specific parameter conditions, this formula can be transformed to a Kappa or Maxwellian function. Considering  the uncertainties both in particle intensity and energy, we fit this general formula well to the representative energy spectra of various suprathermal particle phenomena including solar energetic particles (electrons, protons,  ³He and heavier ions), shocked particles, anomalous cosmic rays, hard X-rays, solar wind suprathermal particles, etc. Therefore, this general spectrum fitting formula would help us to comparatively examine the energy spectrum of different suprathermal particle phenomena and understand their origin, acceleration and transportation.