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Evidence for Energetic Neutral Hydrogen Emission from Solar Particle Events

Mason, G. M. and Greenspan, M. E. and Kanekal, S. G. and Leske, R. A. and Looper, M. D. and Mazur, J. E. and Mewaldt, R. A. (2021) Evidence for Energetic Neutral Hydrogen Emission from Solar Particle Events. Astrophysical Journal, 923 (2). Art. No. 195. ISSN 0004-637X. doi:10.3847/1538-4357/ac2fa2.

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We report the probable detection of energetic neutral hydrogen atoms (ENAs) at >0.8 MeV in several large solar energetic particle events observed between 1997 and 2004. The low Earth orbiting SAMPEX satellite detected transient increases of quasi-trapped equatorial protons beginning typically ∼3 hr after the X-ray flare and lasting for up to several hours. Since the magnetic cutoff rigidity is >10 GV at the magnetic latitude where the particles were observed, we interpret the signal as due to ENAs that penetrate Earth’s magnetic field and charge exchange in the upper atmosphere, whereupon the charged particles may become trapped. One event outside our survey period (2006 December 5) had previously reported solar flare ENAs, the only example of this phenomenon of which we are aware. Although the statistics are limited, the events we report suggest that the ENAs are produced as the flare-associated coronal mass wjection moves through the corona, as concluded previously for the 2006 December 5 event. The finding of ENAs emitted in conjunction with large solar flares opens a new avenue to understanding these events.

Item Type:Article
Related URLs:
URLURL TypeDescription
Mason, G. M.0000-0003-2169-9618
Kanekal, S. G.0000-0001-8157-4281
Leske, R. A.0000-0002-0156-2414
Looper, M. D.0000-0001-8223-1598
Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 2021. 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 August 30; revised 2021 October 11; accepted 2021 October 12; published 2021 December 22. We thank NOAA for the solar and geophysical data and indices used in this paper; and the SOHO Large Angle Spectrometric Coronagraph (LASCO) CME catalog used for CME speeds and the start time of event 4. We thank the referee for helpful suggestions. This work has been supported by NASA grant NNG06GB88G for the SAMPEX data center.
Funding AgencyGrant Number
Subject Keywords:Solar energetic particles; Solar flares; Solar magnetic fields
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Solar energetic particles (1491); Solar flares (1496); Solar magnetic fields (1503)
Record Number:CaltechAUTHORS:20220110-139475200
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Official Citation:G. M. Mason et al 2021 ApJ 923 195
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112811
Deposited By: Tony Diaz
Deposited On:10 Jan 2022 22:56
Last Modified:10 Jan 2022 22:56

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