The Sun’s corona is the birthplace of the solar wind, coronal mass ejections, associated shock waves and solar energetic particles which all are fundamental drivers of space weather. The key physical processes at the origin of these phenomena, i.e. the heating and acceleration of the coronal plasma and energetic particles, have not been clarified to date. By EGU 2020 Parker Solar Probe (PSP) will have completed the fourth of its 24 scheduled orbits around the Sun. The first three orbits have the same perihelia of 35.6 solar radii, while it will move as close as 27.8 solar radii to the Sun during the fourth and fifth orbits. PSP is providing a treasure trove worth of in-situ and remote sensing data. The data from the first two orbits, that become public on November 12, 2019, have already revealed phenomena never seen before. Solar Orbiter (SO) is scheduled to launch in February 2020. The in-situ instruments will become fully operational by May 2020. The remote sensing instruments will be switched on later. Combining the PSP observations with data from SO, with remote sensing observations from SDO, STEREO and Proba2, with other in-situ data, e.g., from ACE and DSCOVR, with ground-based observations and with theoretical models will be a challenging and exciting task. This session invites oral and poster contributions on all aspects of research addressed to the exploration of our near-Sun environment, with special focus on the new observations from PSP and topics related to the latest status of the SO mission.

Convener: Volker Bothmer | Co-conveners: Olga Malandraki, Nour E. Raouafi, Alexis Rouillard, Marco Velli
| Attendance Thu, 07 May, 14:00–15:45 (CEST)

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Chat time: Thursday, 7 May 2020, 14:00–15:45

Chairperson: Volker Bothmer
D2949 |
| Highlight
Yannis Zouganelis, Daniel Mueller, Chris St Cyr, Holly Gilbert, and Teresa Nieves-Chinchilla

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

How to cite: Zouganelis, Y., Mueller, D., St Cyr, C., Gilbert, H., and Nieves-Chinchilla, T.: Solar Orbiter: Europe's mission to the Sun, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22164, https://doi.org/10.5194/egusphere-egu2020-22164, 2020.

D2950 |
| Highlight
Sami K. Solanki, Johann Hirzberger, Thomas Wiegelmann, Achim Gandorfer, Joachim Woch, and José Carlos del Toro Iniesta

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

How to cite: Solanki, S. K., Hirzberger, J., Wiegelmann, T., Gandorfer, A., Woch, J., and del Toro Iniesta, J. C.: The SO/PHI instrument on Solar Orbiter and its data products , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17904, https://doi.org/10.5194/egusphere-egu2020-17904, 2020.

D2951 |
| Highlight
Milan Maksimovic, Jan Souček, Stuart D. Bale, Xavier Bonnin, Thomas Chust, Yuri Khotyaintsev, Matthieu Kretzschmar, Dirk Plettemeier, Manfred Steller, and Štěpán Štverák

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

How to cite: Maksimovic, M., Souček, J., Bale, S. D., Bonnin, X., Chust, T., Khotyaintsev, Y., Kretzschmar, M., Plettemeier, D., Steller, M., and Štverák, Š.: The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter : Capabilities, Performance and First results., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5800, https://doi.org/10.5194/egusphere-egu2020-5800, 2020.

D2952 |
Robert F. Wimmer-Schweingruber, Javier Rodriguez-Pacheco, Stephan Böttcher, Ignacio Cernuda, Nina Dresing, Wolfgang Dröge, Sandra Eldrum, Francisco Espinose Lara, Raul Gomez-Herrero, Bernd Heber, George Ho, Andreas Klassen, Alexander Kollhoff, Shrinivasrao Kulkarni, Gottfried Mann, César Martin, Glenn Mason, Daniel Pacheco, Manuel Prieto, and Sebastian Sanchez and the Robert F. Wimmer-Schweingruber

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

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

How to cite: Wimmer-Schweingruber, R. F., Rodriguez-Pacheco, J., Böttcher, S., Cernuda, I., Dresing, N., Dröge, W., Eldrum, S., Espinose Lara, F., Gomez-Herrero, R., Heber, B., Ho, G., Klassen, A., Kollhoff, A., Kulkarni, S., Mann, G., Martin, C., Mason, G., Pacheco, D., Prieto, M., and Sanchez, S. and the Robert F. Wimmer-Schweingruber: Energetic Particles in the Inner Heliosphere: Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22044, https://doi.org/10.5194/egusphere-egu2020-22044, 2020.

D2953 |
Matthieu Kretschmar, Volodya Krasnoselskikh, Jean-Yves Brochot, Guillaume Jannet, Thierry Dudok de Wit, Clara Froment, Milan Maksimovic, Thomas Chust, Olivier Le Contel, Jan Soucek, and David Pisa

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

How to cite: Kretschmar, M., Krasnoselskikh, V., Brochot, J.-Y., Jannet, G., Dudok de Wit, T., Froment, C., Maksimovic, M., Chust, T., Le Contel, O., Soucek, J., and Pisa, D.: First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19143, https://doi.org/10.5194/egusphere-egu2020-19143, 2020.

D2954 |
Natalia Zambrana Prado, Eric Buchlin, and Hardi Peter

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

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

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

How to cite: Zambrana Prado, N., Buchlin, E., and Peter, H.: Relative abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20154, https://doi.org/10.5194/egusphere-egu2020-20154, 2020.

D2955 |
Philippe Louarn, andrei fedorov, and Christopher Owen and the SWA/PAS team

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

How to cite: Louarn, P., fedorov, A., and Owen, C. and the SWA/PAS team: The Proton and Alpha Sensor (PAS) of Solar Orbiter Mission: design, operation, scientific return simulation, and first flight results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4720, https://doi.org/10.5194/egusphere-egu2020-4720, 2020.

D2956 |
| Highlight
Justin Kasper and the On behalf of the SWEAP Investigation science team

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

How to cite: Kasper, J. and the On behalf of the SWEAP Investigation science team: Plasma and magnetic field dynamics in the young solar wind, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19314, https://doi.org/10.5194/egusphere-egu2020-19314, 2020.

D2957 |
| Highlight
Russell Howard, Guillermo Stenborg, David Malaspina, Jamey Szalay, and Petr Pokorny

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

How to cite: Howard, R., Stenborg, G., Malaspina, D., Szalay, J., and Pokorny, P.: The Dust Environment in the Inner Heliosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19398, https://doi.org/10.5194/egusphere-egu2020-19398, 2020.

D2958 |
| Highlight
Nathan Schwadron and the PSP-ISʘIS Group

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

How to cite: Schwadron, N. and the PSP-ISʘIS Group: Energetic Particle Environment near the Sun from Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6063, https://doi.org/10.5194/egusphere-egu2020-6063, 2020.

D2959 |
| Highlight
Mihir Desai and the Parker Solar Probe ISOIS, FIELDS & SWEAP Team

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

How to cite: Desai, M. and the Parker Solar Probe ISOIS, FIELDS & SWEAP Team: Properties of Suprathermal-through-Energetic He Ions Associated with Stream Interaction Regions Observed over Parker Solar Probe’s First Two Orb¬¬its, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1901, https://doi.org/10.5194/egusphere-egu2020-1901, 2020.

D2960 |
Christopher Chen and the PSP FIELDS and SWEAP Teams

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

How to cite: Chen, C. and the PSP FIELDS and SWEAP Teams: The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11550, https://doi.org/10.5194/egusphere-egu2020-11550, 2020.

D2961 |
Teresa Nieves-Chinchilla, Adam Szabo, Kelly E. Korreck, Nathalia Alzate, Laura A. Balmaceda, Benoit Lavraud, Kristoff Paulson, Ayris A. Narock, Samantha Wallace, Lan K. Jian, Janet G. Luhman, Huw Morgan, Aleida Higginson, and Charles N. Arge and the PSP team

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

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

How to cite: Nieves-Chinchilla, T., Szabo, A., Korreck, K. E., Alzate, N., Balmaceda, L. A., Lavraud, B., Paulson, K., Narock, A. A., Wallace, S., Jian, L. K., Luhman, J. G., Morgan, H., Higginson, A., and Arge, C. N. and the PSP team: Analysis of the Internal structure of the Streamer Blow Out Observed by the Parker Solar Probe during the First Solar Encounter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22182, https://doi.org/10.5194/egusphere-egu2020-22182, 2020.

D2962 |
Nicolas Poirier, Athanasios Kouloumvakos, Alexis P. Rouillard, Rui Pinto, Angelos Vourlidas, Guillermo Stenborg, Emeline Valette, Russell A. Howard, Phillip Hess, Arnaud Thernisien, Nathan Rich, Léa Griton, Mikel Indurain, Nour-Edine Raouafi, Michael Lavarra, and Victor Réville

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

How to cite: Poirier, N., Kouloumvakos, A., Rouillard, A. P., Pinto, R., Vourlidas, A., Stenborg, G., Valette, E., Howard, R. A., Hess, P., Thernisien, A., Rich, N., Griton, L., Indurain, M., Raouafi, N.-E., Lavarra, M., and Réville, V.: The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11552, https://doi.org/10.5194/egusphere-egu2020-11552, 2020.

D2963 |
Tereza Durovcova and the PSP

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.

D2964 |
Malte Hörlöck, Bernd Heber, and Johannes Marquardt

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

How to cite: Hörlöck, M., Heber, B., and Marquardt, J.: GEANT 4 Simulation of the Helios E6 - Proton Contamination of Relativistic Electron Measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4911, https://doi.org/10.5194/egusphere-egu2020-4911, 2020.

D2965 |
Yuri V. Khotyaintsev, Andris Vaivads, Daniel B. Graham, Niklas J. T. Edberg, Erik P. G. Johansson, Milan Maksimovic, Stuart D. Bale, Thomas Chust, Matthieu Kretzschmar, and Jan Soucek

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

How to cite: Khotyaintsev, Y. V., Vaivads, A., Graham, D. B., Edberg, N. J. T., Johansson, E. P. G., Maksimovic, M., Bale, S. D., Chust, T., Kretzschmar, M., and Soucek, J.: Initial in-flight performance results from Solar Orbiter RPW/BIAS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14874, https://doi.org/10.5194/egusphere-egu2020-14874, 2020.

D2966 |
Gaetan Gauthier, Catherine Krafft, and Philippe Savoini

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

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

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

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

How to cite: Gauthier, G., Krafft, C., and Savoini, P.: Electromagnetic radiation from upper-hybrid wave turbulence driven by electron beams in solar plasmas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18183, https://doi.org/10.5194/egusphere-egu2020-18183, 2020.

D2967 |
Karine Issautier, Mingzhe Liu, Michel Moncuquet, Nicole Meyer-Vernet, Milan Maksimovic, Stuart Bale, and Marc Pulupa

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

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

How to cite: Issautier, K., Liu, M., Moncuquet, M., Meyer-Vernet, N., Maksimovic, M., Bale, S., and Pulupa, M.: Large-scale electron solar wind parameters of the inner heliosphere with Parker Solar Probe/FIELDS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18573, https://doi.org/10.5194/egusphere-egu2020-18573, 2020.

D2968 |
Jan Soucek, Ludek Uhlir, Radek Lan, David Pisa, Ivana Kolmasova, Ondrej Santolik, Vratislav Krupar, Oksana Kruparova, Milan Maksimovic, Matthieu Kretzschmar, Yuri Khotyaintsev, and Thomas Chust

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

How to cite: Soucek, J., Uhlir, L., Lan, R., Pisa, D., Kolmasova, I., Santolik, O., Krupar, V., Kruparova, O., Maksimovic, M., Kretzschmar, M., Khotyaintsev, Y., and Chust, T.: The RPW Time Domain Sampler (TDS) on Solar Orbiter: In-flight performance and first data , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18888, https://doi.org/10.5194/egusphere-egu2020-18888, 2020.

D2969 |
Robert Allen, George Ho, Lan Jian, David Lario, Dusan Odstrcil, Charles Arge, Sam Badman, Stuart Bale, Anthony Case, Eric Christian, Christina Cohen, Carl Henney, Matthew Hill, Shaela Jones, Justin Kasper, Kelly Korreck, David Malaspina, David McComas, Nour Raouafi, and Michael Stevens

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

How to cite: Allen, R., Ho, G., Jian, L., Lario, D., Odstrcil, D., Arge, C., Badman, S., Bale, S., Case, A., Christian, E., Cohen, C., Henney, C., Hill, M., Jones, S., Kasper, J., Korreck, K., Malaspina, D., McComas, D., Raouafi, N., and Stevens, M.: Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21075, https://doi.org/10.5194/egusphere-egu2020-21075, 2020.

D2970 |
Daniel Pacheco, Angels Aran, Raul Gomez-Herrero, Neus Agueda, David Lario, Bernd Heber, Blai Sanahuja, Nicolas Wijsen, and Robert F. Wimmer-Schweingruber

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

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

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

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

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

How to cite: Pacheco, D., Aran, A., Gomez-Herrero, R., Agueda, N., Lario, D., Heber, B., Sanahuja, B., Wijsen, N., and Wimmer-Schweingruber, R. F.: Seeing Helios electron data through the eyes of Solar Orbiter: modelling the angular response of EPD/EPT and its application to the full inversion of Helios events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21407, https://doi.org/10.5194/egusphere-egu2020-21407, 2020.

D2971 |
Niclas Mrotzek and Volker Bothmer

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


How to cite: Mrotzek, N. and Bothmer, V.: High resolution multi-viewpoint observations of CME kinematics and dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22532, https://doi.org/10.5194/egusphere-egu2020-22532, 2020.

D2972 |
Andreas Weiss, Christian Möstl, Teresa Nieves-Chinchilla, Tanja Amerstorfer, Erika Palmerio, Martin Reiss, Rachel Bailey, Jürgen Hinterreiter, Ute Amerstorfer, and Maike Bauer

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

How to cite: Weiss, A., Möstl, C., Nieves-Chinchilla, T., Amerstorfer, T., Palmerio, E., Reiss, M., Bailey, R., Hinterreiter, J., Amerstorfer, U., and Bauer, M.: Modelling coronal mass ejection flux ropes signatures using Approximate Bayesian Computation: applications to Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8398, https://doi.org/10.5194/egusphere-egu2020-8398, 2020.

D2973 |
Jonathan Niehof and Nathan Schwadron and the PSP/IS☉IS team

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

How to cite: Niehof, J. and Schwadron, N. and the PSP/IS☉IS team: Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11111, https://doi.org/10.5194/egusphere-egu2020-11111, 2020.

D2974 |
Maximilian Bruedern, Nina Dresing, Bernd Heber, Lars Berger, Alexander Kollhoff, and Patrick Kühl

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

How to cite: Bruedern, M., Dresing, N., Heber, B., Berger, L., Kollhoff, A., and Kühl, P.: Determination of Solar Energetic Particle anisotropies based on four-sector measurements - Study based on STEREO/SEPT in preperation of SolO/EPT, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17554, https://doi.org/10.5194/egusphere-egu2020-17554, 2020.

D2975 |
Allan Macneil, Mathew Owens, Robert Wicks, Mike Lockwood, Matthew Lang, and Sarah Bentley

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

How to cite: Macneil, A., Owens, M., Wicks, R., Lockwood, M., Lang, M., and Bentley, S.: Radial Evolution of Inverted Heliospheric Magnetic Field Between 0.3 and 1 AU, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18502, https://doi.org/10.5194/egusphere-egu2020-18502, 2020.

D2976 |
Valentina Zharkova, Qian Xia, Joel Dahlin, and Spiro Antiochos

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

How to cite: Zharkova, V., Xia, Q., Dahlin, J., and Antiochos, S.: Acceleration of particles in different parts of erupting coronal mass ejections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20181, https://doi.org/10.5194/egusphere-egu2020-20181, 2020.

D2977 |
Johannes Marquardt, Bernd Heber, Robert Elftmann, and Robert Wimmer-Schweingruber

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

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

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

How to cite: Marquardt, J., Heber, B., Elftmann, R., and Wimmer-Schweingruber, R.: Energy spectra of carbon and oxygen - Predictions from HELIOS E6 for Solar Orbiter HET , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5027, https://doi.org/10.5194/egusphere-egu2020-5027, 2020.

D2978 |
Catherine Krafft and Alexander Volokitin

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

How to cite: Krafft, C. and Volokitin, A.: Efficiency of electromagnetic emission by electrostatic turbulence in solar plasmas with density inhomogeneities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21572, https://doi.org/10.5194/egusphere-egu2020-21572, 2020.

D2979 |
Gottfried Mann, Christian Vocks, Mario Bisi, Eoin Carley, Bartosz Dabrowski, Richard Fallows, Peter Gallagher, Andrzej Krankowski, Jasmina Magdalenic, Christophe Marque, Diana Morosan, Hanna Rothkaehl, and Pietro Zucca

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

How to cite: Mann, G., Vocks, C., Bisi, M., Carley, E., Dabrowski, B., Fallows, R., Gallagher, P., Krankowski, A., Magdalenic, J., Marque, C., Morosan, D., Rothkaehl, H., and Zucca, P.: Type III Radio Bursts and Langmuir Wave Excitation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7595, https://doi.org/10.5194/egusphere-egu2020-7595, 2020.

D2980 |
George Ho, Glenn Mason, Robert Wimmer-Schweingruber, and Javier Rodríguez-Pacheco

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

How to cite: Ho, G., Mason, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Energetic and Suprathermal Particle Composition Measurements from Solar Orbiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20919, https://doi.org/10.5194/egusphere-egu2020-20919, 2020.

D2981 |
Thomas Chust, Olivier Le Contel, Matthieu Berthomier, Alessandro Retinò, Fouad Sahraoui, Alexis Jeandet, Paul Leroy, Jean-Christophe Pellion, Véronique Bouzid, Bruno Katra, Rodrigue Piberne, Yuri Khotyaintsev, Andris Vaivads, Volodya Krasnoselskikh, Matthieu Kretzschmar, Jan Souček, Ondrej Santolík, Milan Maksimovic, and Stuart D. Bale and the MMS team

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

How to cite: Chust, T., Le Contel, O., Berthomier, M., Retinò, A., Sahraoui, F., Jeandet, A., Leroy, P., Pellion, J.-C., Bouzid, V., Katra, B., Piberne, R., Khotyaintsev, Y., Vaivads, A., Krasnoselskikh, V., Kretzschmar, M., Souček, J., Santolík, O., Maksimovic, M., and Bale, S. D. and the MMS team: The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10050, https://doi.org/10.5194/egusphere-egu2020-10050, 2020.

D2982 |
Vladimir Krasnoselskikh and the PSP Magnetic Structures

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

How to cite: Krasnoselskikh, V. and the PSP Magnetic Structures: Localized magnetic field structures and their boundaries in the near-Sun solar wind from Parker Solar Probe measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20293, https://doi.org/10.5194/egusphere-egu2020-20293, 2020.