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PSP/IS⊙IS observations of the 29 November 2020 solar energetic particle event

Cohen, C. M. S. and Christian, E. R. and Cummings, A. C. and Davis, A. J. and Desai, M. I. and de Nolfo, G. A. and Giacalone, J. and Hill, M. E. and Joyce, C. J. and Labrador, A. W. and Leske, R. A. and Matthaeus, W. H. and McComas, D. J. and McNutt, R. L., Jr. and Mewaldt, R. A. and Mitchell, D. G. and Mitchell, J. G. and Rankin, J. S. and Roelof, E. C. and Schwadron, N. A. and Stone, E. C. and Szalay, J. R. and Wiedenbeck, M. E. and Vourlidas, A. and Bale, S. D. and Pulupa, M. and MacDowall, R. J. (2021) PSP/IS⊙IS observations of the 29 November 2020 solar energetic particle event. Astronomy and Astrophysics, 656 . Art. No. A29. ISSN 0004-6361. doi:10.1051/0004-6361/202140967.

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Aims. On 29 November 2020, at 12:34 UT, active region 12790 erupted with an M4.4 class flare and a 1700 km s⁻¹ coronal mass ejection. Parker Solar Probe (PSP) was completing its seventh orbit around the Sun and was located at 0.8 au when the Integrated Science Investigation of the Sun (IS⊙IS) measured the ensuing mid-sized solar energetic particle (SEP) event. Not only was this the first SEP event with heavy ions above 10 MeV nuc⁻¹ to be measured by IS⊙IS, it was also measured by several spacecraft positioned around the Sun, making it the first circumsolar event of solar cycle 25. Here we describe an overview of the SEP event characteristics at PSP. Methods. Fluence spectra for electrons, H, He, O, and Fe were calculated for the decay portion of the event. For the entire time period of the event, it was possible to calculate fluence spectra for electrons, O, and Fe only due to instrumental mode changes in one of the IS⊙IS telescopes, affecting H and He during the period of peak intensities. Using higher time resolution data, we also studied the onset of the event and temporal variations in the particle intensities at the shock and during the magnetic cloud passage. Results. During the decay, the ion spectra are consistent with power laws at low energies with an exponential rollover at a few MeV nuc⁻¹, while the electron spectrum is consistent with a power law of index −5.3. Based on fits to the spectra, Fe/O and He/H abundance ratios as a function of energy are calculated and found to be nominal for large SEP events at hundreds of keV/nuc, but decrease strongly with increasing energy. The full-event spectra for O and Fe have similar shapes to those of the decay, but with higher roll-over energies. The electron spectrum for the full event is harder with an index of −3.4 and there is some evidence of higher energy components near ∼2 MeV and above ∼4 MeV. Despite the spacecraft being tilted 45° with respect to the nominal orientation of the spacecraft’s long axis pointed towards the Sun, there is some anisotropy apparent in MeV protons during the onset of the event. Velocity dispersion is also evident, consistent with a solar release time of 13:15 UT and pathlength of 1.3 au. The arrival of the related magnetic cloud resulted in the suppression of SEP intensities, although a brief increase in particle intensities suggests PSP moved out of the cloud for ∼30 min. This appears to be the first medium-sized event in the rise of cycle 25 activity, with additional large events likely to occur. Additional details of the event beyond this overview can be found in several related papers.

Item Type:Article
Related URLs:
URLURL TypeDescription Information ItemSTEREO/SECCHI data ItemIS⊙IS data and visualization tools ItemNASA Space Physics Data Facility ItemGOES X-ray data
Cohen, C. M. S.0000-0002-0978-8127
Christian, E. R.0000-0003-2134-3937
Cummings, A. C.0000-0002-3840-7696
Davis, A. J.0000-0002-9922-8915
Desai, M. I.0000-0002-7318-6008
de Nolfo, G. A.0000-0002-3677-074X
Giacalone, J.0000-0002-0850-4233
Hill, M. E.0000-0002-5674-4936
Joyce, C. J.0000-0002-3841-5020
Labrador, A. W.0000-0001-9178-5349
Leske, R. A.0000-0002-0156-2414
Matthaeus, W. H.0000-0001-7224-6024
McComas, D. J.0000-0001-6160-1158
McNutt, R. L., Jr.0000-0002-4722-9166
Mewaldt, R. A.0000-0003-2178-9111
Mitchell, D. G.0000-0003-1960-2119
Mitchell, J. G.0000-0003-4501-5452
Rankin, J. S.0000-0002-8111-1444
Roelof, E. C.0000-0002-2270-0652
Schwadron, N. A.0000-0002-3737-9283
Stone, E. C.0000-0002-2010-5462
Szalay, J. R.0000-0003-2685-9801
Wiedenbeck, M. E.0000-0002-2825-3128
Vourlidas, A.0000-0002-8164-5948
Bale, S. D.0000-0002-1989-3596
Pulupa, M.0000-0002-1573-7457
MacDowall, R. J.0000-0003-3112-4201
Additional Information:© ESO 2021. Solar Orbiter First Results (Cruise Phase). Received: 31 March 2021 Accepted: 23 August 2021. This work was supported by NASA’s Parker Solar Probe Mission, contract NNN06AA01C. Parker Solar Probe was designed, built, and is now operated by the Johns Hopkins Applied Physics Laboratory as part of NASA’s Living with a Star (LWS) program. Support from the LWS management and technical team has played a critical role in the success of the Parker Solar Probe mission. We thank all the scientists and engineers who have worked hard to make PSP a successful mission. In particular, we thank B. Kecman, W. R. Cook and J. Burnham, without whom the EPI-Hi instrument would not be possible. C. M. S. Cohen thanks T. Nieves-Chinchilla and A. Szabo for their helpful discussions regarding the shock and ICME observations, and N. Dresing for useful ones on electron ESP events. S. D. Bale acknowledges support of the Leverhulme Trust Visiting Professorship program. A. Vourlidas acknowledges support from NASA grants 80NSSC19K1261 and 80NSSC19K0069. The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) was produced by an international consortium of the Naval Research Laboratory (USA), Lockheed Martin Solar and Astrophysics Lab. (USA), NASA Goddard Space Flight Center (USA), Rutherford Appleton Laboratory (UK), University of Birmingham (UK), Max Planck Institute for Solar System Research (Germany), Centre Spatiale de Liège (Belgium), Institut d’Optique Theorique et Appliquée (France), and Institut d’Astrophysique Spatiale (France). STEREO/SECCHI data are available for download at This paper uses data from the CACTus CME catalog, generated and maintained by the SIDC at the Royal Observatory of Belgium. The IS⊙IS data and visualization tools are available to the community at; data are also available via the NASA Space Physics Data Facility ( The GOES X-ray data are available from the National Centers for Environmental Information (
Group:Astronomy Department, Space Radiation Laboratory
Funding AgencyGrant Number
Leverhulme TrustUNSPECIFIED
Subject Keywords:Sun: particle emission / Sun: activity / solar-terrestrial relations
Record Number:CaltechAUTHORS:20211214-82701000
Persistent URL:
Official Citation:PSP/IS⊙IS observations of the 29 November 2020 solar energetic particle event C. M. S. Cohen, E. R. Christian, A. C. Cummings, A. J. Davis, M. I. Desai, G. A. de Nolfo, J. Giacalone, M. E. Hill, C. J. Joyce, A. W. Labrador, R. A. Leske, W. H. Matthaeus, D. J. McComas, R. L. McNutt, R. A. Mewaldt, D. G. Mitchell, J. G. Mitchell, J. S. Rankin, E. C. Roelof, N. A. Schwadron, E. C. Stone, J. R. Szalay, M. E. Wiedenbeck, A. Vourlidas, S. D. Bale, M. Pulupa and R. J. MacDowall A&A, 656 (2021) A29 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112438
Deposited By: George Porter
Deposited On:15 Dec 2021 17:55
Last Modified:01 Feb 2022 22:54

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