Issue |
A&A
Volume 656, December 2021
Solar Orbiter First Results (Cruise Phase)
|
|
---|---|---|
Article Number | A20 | |
Number of page(s) | 16 | |
Section | The Sun and the Heliosphere | |
DOI | https://doi.org/10.1051/0004-6361/202140937 | |
Published online | 14 December 2021 |
The first widespread solar energetic particle event observed by Solar Orbiter on 2020 November 29
1
Institut für Experimentelle und Angewandte Physik, Christian Albrechts-Universität zu Kiel, Kiel, Germany
e-mail: kollhoff@physik.uni-kiel.de
2
IRAP, Université Toulouse III – Paul Sabatier, CNRS, CNES, Toulouse, France
3
NASA Goddard Space Flight Center, Heliophysics Science Division, Greenbelt, MD 20771, USA
4
Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
5
Universidad de Alcalá, Alcalá de Henares, Spain
6
National Observatory of Athens, IAASARS, Metaxa and Vas. Pavlou str., Pedeli, 15236 Athens, Greece
7
Department of Astronomy, University of Maryland, College Park, MD 20742, USA
8
NASA/HQ, 300 Hidden Figures Way SW, Washington, DC 20546, USA
9
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
10
California Institute of Technology, Pasadena, CA, USA
11
University of Central Lancashire, Lancashire, UK
12
Institute for Space Astrophysics and Planetology, INAF, Roma, Italy
13
University of Helsinki, Helsinki, Finland
14
Dep. Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Barcelona, Spain
15
Southwest Research Institute, San Antonio, TX 78238, USA
16
Centre for mathematical Plasma-Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
17
European Space Astronomy Center, Villanueva de la Cañada, 28692 Madrid, Spain
18
Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
19
Department of Physics and Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
20
Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County, Baltimore, MD, USA
21
Department of Physics, Imperial College London, London SW7 2AZ, UK
22
Swedish Institute of Space Physics (IRF), Uppsala 75121, Sweden
23
Radboud Radio Lab, Department of Astrophysics, Radboud University, Nijmegen, The Netherlands
24
Space and Plasma Physics, Department of Physics and Astronomy, Uppsala University, Uppsala 75120, Sweden
Received:
30
March
2021
Accepted:
24
May
2021
Context. On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (≲1 AU) heliosphere. Relativistic electrons as well as protons with energies > 50 MeV were observed by Solar Orbiter (SolO), Parker Solar Probe, the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts.
Aims. We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event.
Methods. Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium.
Results. We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1 AU. The particle onset delays observed at the different spacecraft are larger as the flare–footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved.
Key words: Sun: particle emission / Sun: heliosphere / Sun: coronal mass ejections (CMEs) / Sun: flares / interplanetary medium
© A. Kollhoff et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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