Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter
We performed a survey of ^3 He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 ^3 He-rich events, each showing clear ^3 He enhancements above the background and ^3 He/ ^4 He abundance ratios greater than 1 in at l...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adbae7 |
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| author | A. Kouloumvakos G. M. Mason G. C. Ho R. C. Allen J. Rodriguez-Pacheco R. F. Wimmer-Schweingruber |
| author_facet | A. Kouloumvakos G. M. Mason G. C. Ho R. C. Allen J. Rodriguez-Pacheco R. F. Wimmer-Schweingruber |
| author_sort | A. Kouloumvakos |
| collection | DOAJ |
| description | We performed a survey of ^3 He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 ^3 He-rich events, each showing clear ^3 He enhancements above the background and ^3 He/ ^4 He abundance ratios greater than 1 in at least one energy channel in the range from 193.2 keV nucleon ^−1 to 8.74 MeV nucleon ^−1 . The analysis of the events’ abundance ratios shows characteristics of impulsive solar energetic particle events with ^3 He/ ^4 He ∼ 3.1 and Fe/O ∼ 1.3. We observe an energy dependence in the ^3 He/ ^4 He ratio, which increases with energy, while the Fe/O ratios are almost constant with energy. We also found that six events in our list have extremely high ^3 He content (e.g., ^3 He/C–Fe ratios in the range 25–62). These events show curved ^3 He and heavy nuclei spectra that roll over at higher energies and flatten toward low energy. Their spectral forms can be reasonably fit with simple exponentials with a ^3 He rollover energy in the range of a few hundred keV per nucleon and a C–Fe rollover energy ∼2–3 times lower. The differences in spectral rollover energy lead to a strong energy dependence of the ratio ^3 He/C–Fe, rising sharply with energy. We conclude that the features of these events with extremely high ^3 He content have a reasonable likelihood of depicting the initial acceleration process, which is driven by magnetic reconnection in flaring loops near the solar surface. |
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| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-2fc0ed2c8c744339a0b4e839211edb742025-08-20T01:54:12ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198316710.3847/1538-4357/adbae7Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar OrbiterA. Kouloumvakos0https://orcid.org/0000-0001-6589-4509G. M. Mason1https://orcid.org/0000-0003-2169-9618G. C. Ho2https://orcid.org/0000-0003-1093-2066R. C. Allen3https://orcid.org/0000-0003-2079-5683J. Rodriguez-Pacheco4https://orcid.org/0000-0002-4240-1115R. F. Wimmer-Schweingruber5https://orcid.org/0000-0002-7388-173XThe Johns Hopkins University Applied Physics Laboratory , 11101 Johns Hopkins Road, Laurel, MD 20723, USAThe Johns Hopkins University Applied Physics Laboratory , 11101 Johns Hopkins Road, Laurel, MD 20723, USASouthwest Research Institute , 6220 Culebra Road, San Antonio, TX 78238, USASouthwest Research Institute , 6220 Culebra Road, San Antonio, TX 78238, USAUniversidad de Alcalá , Space Research Group, 28805 Alcalá de Henares, SpainInstitute of Experimental and Applied Physics, Christian-ALbrechts-University Kiel , 24118 Kiel, GermanyWe performed a survey of ^3 He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 ^3 He-rich events, each showing clear ^3 He enhancements above the background and ^3 He/ ^4 He abundance ratios greater than 1 in at least one energy channel in the range from 193.2 keV nucleon ^−1 to 8.74 MeV nucleon ^−1 . The analysis of the events’ abundance ratios shows characteristics of impulsive solar energetic particle events with ^3 He/ ^4 He ∼ 3.1 and Fe/O ∼ 1.3. We observe an energy dependence in the ^3 He/ ^4 He ratio, which increases with energy, while the Fe/O ratios are almost constant with energy. We also found that six events in our list have extremely high ^3 He content (e.g., ^3 He/C–Fe ratios in the range 25–62). These events show curved ^3 He and heavy nuclei spectra that roll over at higher energies and flatten toward low energy. Their spectral forms can be reasonably fit with simple exponentials with a ^3 He rollover energy in the range of a few hundred keV per nucleon and a C–Fe rollover energy ∼2–3 times lower. The differences in spectral rollover energy lead to a strong energy dependence of the ratio ^3 He/C–Fe, rising sharply with energy. We conclude that the features of these events with extremely high ^3 He content have a reasonable likelihood of depicting the initial acceleration process, which is driven by magnetic reconnection in flaring loops near the solar surface.https://doi.org/10.3847/1538-4357/adbae7Solar physicsSolar particle emissionSolar abundances |
| spellingShingle | A. Kouloumvakos G. M. Mason G. C. Ho R. C. Allen J. Rodriguez-Pacheco R. F. Wimmer-Schweingruber Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter The Astrophysical Journal Solar physics Solar particle emission Solar abundances |
| title | Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter |
| title_full | Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter |
| title_fullStr | Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter |
| title_full_unstemmed | Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter |
| title_short | Solar Energetic Particle Events with Extremely High 3He Content Observed by Solar Orbiter |
| title_sort | solar energetic particle events with extremely high 3he content observed by solar orbiter |
| topic | Solar physics Solar particle emission Solar abundances |
| url | https://doi.org/10.3847/1538-4357/adbae7 |
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