Solar energetic particle events with extremely high 3He content observed by Solar Orbiter
We performed a survey of 3He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 3He-rich events, each showing clear 3He enhancements above the background and 3He/4He abundance ratios greater than 1 in at least one en...
| Authors: | ; ; ; ; ; |
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| Format: | Article |
| Publication date: | 2025 |
| Country: | España |
| Institution: | Universidad de Alcalá (UAH) |
| Repository: | e_Buah Biblioteca Digital Universidad de Alcalá |
| Language: | English |
| OAI Identifier: | oai:ebuah.uah.es:10017/67372 |
| Online Access: | http://hdl.handle.net/10017/67372 https://dx.doi.org/10.3847/1538-4357/adbae7 |
| Access Level: | Open access |
| Keyword: | Astronomía Física Astronomy Physics |
| Summary: | We performed a survey of 3He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 3He-rich events, each showing clear 3He enhancements above the background and 3He/4He 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 3He/4He ∼ 3.1 and Fe/O ∼ 1.3. We observe an energy dependence in the 3He/4He 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 3He content (e.g., 3He/C–Fe ratios in the range 25–62). These events show curved 3He 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 3He 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 3He/C–Fe, rising sharply with energy. We conclude that the features of these events with extremely high 3He 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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