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Multi-spacecraft Observations of Gradual Solar Energetic Particle Events with Enhanced 3He Abundance
  • +14
  • Radoslav Bucik,
  • Glenn Mason,
  • Raúl Gómez-Herrero,
  • Maher Dayeh,
  • Mihir Desai,
  • Christina Cohen,
  • David Lario,
  • Laura Balmaceda,
  • Vratislav Krupar,
  • Mark Wiedenbeck,
  • Robert Wimmer-Schweingruber,
  • George Ho,
  • Javier Rodriguez-Pacheco,
  • Nariaki Nitta,
  • Patrick Kühl,
  • Zigong Xu,
  • Tilaye Asfaw
Radoslav Bucik
Southwest Research Institute, Southwest Research Institute

Corresponding Author:radoslav.bucik@swri.org

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Glenn Mason
Johns Hopkins University Applied Physics Laboratory, Johns Hopkins University Applied Physics Laboratory
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Raúl Gómez-Herrero
University of Alcalá, University of Alcalá
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Maher Dayeh
Southwest Research Institute, Southwest Research Institute
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Mihir Desai
Southwest Research Institute, Southwest Research Institute
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Christina Cohen
California Institute of Technology, California Institute of Technology
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David Lario
NASA Goddard Space Flight Center, NASA Goddard Space Flight Center
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Laura Balmaceda
George Mason University Fairfax, George Mason University Fairfax
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Vratislav Krupar
NASA Goddard Space Flight Center, NASA Goddard Space Flight Center
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Mark Wiedenbeck
Jet Propulsion Laboratory, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology
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Robert Wimmer-Schweingruber
University of Kiel, University of Kiel
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George Ho
Johns Hopkins University Applied Physics Laboratory, Johns Hopkins University Applied Physics Laboratory
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Javier Rodriguez-Pacheco
University of Alcalá, University of Alcalá
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Nariaki Nitta
Lockheed Martin Advanced Technology Center, Lockheed Martin Advanced Technology Center
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Patrick Kühl
University of Kiel, University of Kiel
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Zigong Xu
University of Kiel, University of Kiel
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Tilaye Asfaw
NASA JSC/Leidos, NASA JSC/Leidos
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Abstract

Flare suprathermal ions with enhanced 3He and heavy-ion abundances are an essential component of the seed population accelerated by CME-driven shocks in gradual solar energetic particle (GSEP) events. However, the mechanisms through which CME-driven shocks gain access to flare suprathermals and produce spectral and abundance variations in GSEP events remain largely unexplored. We report two recent GSEP events: one observed by Solar Orbiter on 2020 Nov 24 (the first GSEP event on Solar Orbiter) and the other by ACE on 2021 May 29 (the most intense GOES proton event in the present solar cycle). The events were preceded by impulsive SEP (ISEP) events. Abundances and energy spectra are markedly different in the examined events at < 1 MeV/nucleon. For example, in the May event, Fe/O is typical of ISEP events, a factor of 100 to 10 higher than Fe/O in the November event. 3He abundance in the November event is high, typical of ISEP events, while in the May event, it is much lower, though finite. The May event shows a hard 4He spectrum with a power-law index of −1.6, and the November event a soft spectrum with an index of −3.5. The events were associated with halo CMEs with speeds around 900 km/s. The November event was also measured by Parker Solar Probe and the May event by STEREO-A and Solar Orbiter. This paper discusses the origin of vastly different abundances and spectral shapes in terms of variable remnant population from preceding ISEP events. Furthermore, we discuss a possible direct contribution from parent flares.