Temperature in solar sources of 3He-rich solar energetic particles and relation to ion abundances

Bučík, R., Mulay, S. M. , Mason, G. M., Nitta, N. V., Desai, M. I. and Dayeh, M. A. (2021) Temperature in solar sources of 3He-rich solar energetic particles and relation to ion abundances. Astrophysical Journal, 908(2), 243. (doi: 10.3847/1538-4357/abd62d)

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3He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass (Q/M) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of 3He-rich SEPs. This study examines the relation between the suprathermal ( < 0.2 MeV/nuc) abundances of the He-Fe ions measured on the Advanced Composition Explorer and temperature in the solar sources for 24 3He-rich SEP events in the period 2010-2015. The differential emission measure technique is applied to derive the temperature of the source regions from the extreme ultraviolet imaging observations on the Solar Dynamics Observatory. The obtained temperature distribution peaks at 2.0-2.5 MK that is surprisingly consistent with earlier findings based on in-situ elemental abundance or charge state measurements. We have found a significant anti-correlation between 3He/4He ratio and solar source temperature with a coefficient -0.6. It is most likely caused by non-charge-stripping processes, as both isotopes would be fully ionized in the inferred temperature range. This study shows that the elemental ratios 4He/O, N/O, Ne/O, Si/O, S/O, Ca/O, Fe/O generally behave with temperature as expected from abundance enhancement calculations at ionization equilibrium. The C and Mg, the two species with small changes in the Q/M ratio in the obtained temperature range, show no such behavior with temperature and could be influenced by similar processes as for the 3He/4He ratio.

Item Type:Articles
Additional Information:Work at SwRI was supported by NASA grants 80NSSC19K0079 and 80NSSC20K1255, and at JHU/APL by NASA grant NNX17AC05G/125225. This study benefits from discussions within the International Space Science Institute (ISSI) Team ID 425 ‘Origins of 3He-rich SEPs’. CHIANTI is a collaborative project involving George Mason University, the University of Michigan (USA), University of Cambridge (UK), and NASA Goddard Space Flight Center (USA).
Glasgow Author(s) Enlighten ID:Mulay, Dr Sargam
Authors: Bučík, R., Mulay, S. M., Mason, G. M., Nitta, N. V., Desai, M. I., and Dayeh, M. A.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN (Online):1538-4357
Copyright Holders:Copyright © 2021 The American Astronomical Society
First Published:First published in Astrophysical Journal 908(2):243
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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