PSP/IS⊙IS Observation of a Solar Energetic Particle Event Associated with a Streamer Blowout Coronal Mass Ejection during Encounter 6

Creators: Getachew, T.; McComas, D. J.; Joyce, C. J.; Palmerio, E.; Christian, E. R.; Cohen, C. M. S.; Desai, M. I.; Giacalone, J.; Hill, M. E.; Matthaeus, W. H.; McNutt, R. L.; Mitchell, D. G.; Mitchell, J. G.; Rankin, J. S.; Roelof, E. C.; Schwadron, N. A.; Szalay, J. R.; Zank, G. P.; Zhao, L.-L.; Lynch, B. J.; Phan, T. D.; Bale, S. D.; Whittlesey, P. L.; Kasper, J. C.

Abstract

In this paper we examine a low-energy solar energetic particle (SEP) event observed by IS⊙IS's Energetic Particle Instrument-Low (EPI-Lo) inside 0.18 au on 2020 September 30. This small SEP event has a very interesting time profile and ion composition. Our results show that the maximum energy and peak in intensity are observed mainly along the open radial magnetic field. The event shows velocity dispersion, and strong particle anisotropies are observed throughout the event, showing that more particles are streaming outward from the Sun. We do not see a shock in the in situ plasma or magnetic field data throughout the event. Heavy ions, such as O and Fe, were detected in addition to protons and 4He, but without significant enhancements in 3He or energetic electrons. Our analysis shows that this event is associated with a slow streamer blowout coronal mass ejection (SBO-CME), and the signatures of this small CME event are consistent with those typical of larger CME events. The time–intensity profile of this event shows that the Parker Solar Probe encountered the western flank of the SBO-CME. The anisotropic and dispersive nature of this event in a shockless local plasma gives indications that these particles are most likely accelerated remotely near the Sun by a weak shock or compression wave ahead of the SBO-CME. This event may represent direct observations of the source of the low-energy SEP seed particle population.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 10; revised 2021 December 1; accepted 2021 December 3; published 2022 February 7. This work was supported as a part of the Integrated Science Investigations of the Sun on NASA's Parker Solar Probe mission, under contract No. NNN06AA01C. The IS⊙IS data and visualization tools are available to the community at https://spacephysics.princeton.edu/missions-instruments/isois; data are also available via the NASA Space Physics Data Facility (https://spdf.gsfc.nasa.gov/). 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 (contract No. NNN06AA01C). Simulation results have been provided by the Community Coordinated Modeling Center at Goddard Space Flight Center through their public Runs on Request system (http://ccmc.gsfc.nasa.gov). The WSA model was developed by C. N. Arge (currently at NASA/GSFC), and the ENLIL model was developed by D. Odstrcil (currently at GMU). We thank the STEREO team for making the SECCHI data used in this study publicly available. E.P.'s research was supported by the NASA LWS Jack Eddy Postdoctoral Fellowship Program, administered by UCAR's Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award No. NNX16AK22G. B.J.L. acknowledges NASA HGI 80NSSC21K0731, NASA LWS 80NSSC21K1325, and NSF AGS 1851945. T.G.'s work was partially supported by the NASA Heliophysics competed Internal Scientist Funding Model.

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