Issue |
A&A
Volume 656, December 2021
Solar Orbiter First Results (Cruise Phase)
|
|
---|---|---|
Article Number | L3 | |
Number of page(s) | 8 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202039883 | |
Published online | 14 December 2021 |
Letter to the Editor
First near-relativistic solar electron events observed by EPD onboard Solar Orbiter
1
Universidad de Alcalá, Space Research Group, 28805 Alcalá de Henares, Spain
e-mail: raul.gomezh@uah.es
2
Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
3
Now at Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
4
Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
5
George Mason University, Fairfax, VA, USA
6
Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
7
National Observatory of Athens, Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, Athens, Greece
8
Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB-IEEC), Barcelona, Spain
9
Southwest Research Institute, 6220 Culebra Rd, San Antonio, TX 78238, USA
10
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
11
Department of Space and Climate Physics, University College London, Holmbury St Mary, Dorking, RH5 6NT, UK
12
Department of Physics, George Washington University, Washington, DC 20052, USA
13
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
14
Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
15
ESA-ESAC, Madrid, Spain European Space Agency (ESA/ESAC), Villafranca del Castillo, 28692 Madrid, Spain
16
INAF Istituto di Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, 00133 Roma, Italy
17
Department of Mathematics/Centre for mathematical Plasma Astrophysics, KU Leuven, Belgium
18
Ioffe Physical-Technical Institute, St. Petersburg 194021, Russia
19
Institute for Theoretical Physics and Astrophysics, University of Würzburg, Würzburg, Germany
20
Department of Physics, Imperial College London, London SW7 2AZ, UK
21
Radboud Radio Lab, Department of Astrophysics/IMAPP-Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
22
Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague, Czech Republic
23
Institut de Recherche en Astrophysique et Planétologie, 9, Avenue du Colonel ROCHE, BP 4346, 31028 Toulouse Cedex 4, France
24
ASTRON–The Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
25
Now at German Aerospace Center (DLR), Department of Extrasolar Planets and Atmospheres, Berlin, Germany
26
Now at DSI Datensicherheit GmbH, Rodendamm 34, 28816 Stuhr, Germany
27
Now at Deutsches Elektronen-Synchrotron (DESY), Platanenallee 6, 15738 Zeuthen, Germany
28
Now at Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
29
Now at University of Colorado/LASP, Boulder, CO, USA
Received:
10
November
2020
Accepted:
4
January
2021
Context. Solar Orbiter, launched in February 2020, started its cruise phase in June 2020, in coincidence with its first perihelion at 0.51 au from the Sun. The in situ instruments onboard, including the Energetic Particle Detector (EPD), operate continuously during the cruise phase enabling the observation of solar energetic particles.
Aims. In situ measurements of the first near-relativistic solar electron events observed in July 2020 by EPD are analyzed and the solar origins and the conditions for the interplanetary transport of these particles investigated.
Methods. Electron observations from keV energies to the near-relativistic range were combined with the detection of type III radio bursts and extreme ultraviolet (EUV) observations from multiple spacecraft in order to identify the solar origin of the electron events. Electron anisotropies and timing as well as the plasma and magnetic field environment were evaluated to characterize the interplanetary transport conditions.
Results. All electron events were clearly associated with type III radio bursts. EUV jets were also found in association with all of them except one. A diversity of time profiles and pitch-angle distributions was observed. Different source locations and different magnetic connectivity and transport conditions were likely involved. The July 11 event was also detected by Wind, separated 107 degrees in longitude from Solar Orbiter. For the July 22 event, the Suprathermal Electron and Proton sensor of EPD allowed for us to not only resolve multiple electron injections at low energies, but it also provided an exceptionally high pitch-angle resolution of a very anisotropic beam. This, together with radio observations of local Langmuir waves suggest a very good magnetic connection during the July 22 event. This scenario is challenged by a high-frequency occultation of the type III radio burst and a nominally non-direct connection to the source; therefore, magnetic connectivity requires further investigation.
Key words: acceleration of particles / Sun: particle emission / Sun: activity
© ESO 2021
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