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Published January 1, 2022 | Accepted Version + Published
Journal Article Open

Variable Ion Compositions of Solar Energetic Particle Events in the Inner Heliosphere: A Field Line Braiding Model with Compound Injections

Abstract

We propose a model for interpreting highly variable ion composition ratios in solar energetic particle (SEP) events recently observed by the Parker Solar Probe (PSP) at 0.3–0.45 au. We use numerical simulations to calculate SEP propagation in a turbulent interplanetary magnetic field with a Kolmogorov power spectrum from large scales down to the gyration scale of energetic particles. We show that when the source regions of different species are offset by a distance comparable to the size of the source regions, the observed energetic particle composition He/H can be strongly variable over more than two orders of magnitude, even if the source ratio is at the nominal value. Assuming a ³He/⁴He source ratio of 10% in impulsive ³He-rich events and the same spatial offset of the source regions, the ³He/⁴He ratio at observation sites also vary considerably. The variability of the ion composition ratios depends on the radial distance, which can be tested by observations made at different radial locations. We discuss the implications of these results on the variability of ion composition of impulsive events and on further PSP and Solar Orbiter observations close to the Sun.

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 July 25; revised 2021 October 9; accepted 2021 October 20; published 2022 January 6. We acknowledge the constructive comments from the reviewer of this paper, which significantly helped improve the clarity of the paper. We thank members of SolFER collaboration for helpful feedback. SolFER is a multi-institutional collaboration for understanding the release of magnetic field energy and associated particle acceleration in flares in the solar corona. F.G., C.M.S.C., M.W., and Q.Z. acknowledge SolFER DRIVE center program with grant number 80NSSC20K0627 and 80HQTR20T0040. F.G. and L.Z. acknowledge support from NASA PSP GI Program 80HQTR21T0117. F.G. and J.G. acknowledge support in part from NASA LWS Program grant 80HQTR21T0005. L.Z. is supported in part by NASA SOLSTICE DRIVE Science Center grant 80NSSC20K0600 and NASA LWS grant 80NSSC21K0417. The work by X.L. and F.G. is funded in part by NASA grant 80NSSC21K1313 and 80HQTR21T0087. The work of C.M.S.C., J.G., R.A.L., M.E.W., and M.D. was supported in part by NASA's Parker Solar Probe Mission under contract NNN06AA01C. J.G. also acknowledges NASA under grant 80NSSC20K1283, and NSF/AGS under grant1931252. Q.Z. also acknowledges support from NASA grant 80HQTR21T0103. F.G. is also supported by DOE through the LDRD program at LANL and office of Fusion Energy Sciences.

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Published - Guo_2022_ApJ_924_22.pdf

Accepted Version - 2110.10880.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023