Positron Processes in the Sun
Positrons play a major role in the emission of solar gamma-rays at energies from a few hundred keV to >1 GeV. Although the processes leading to positron production in the solar atmosphere are well known, the origin of the underlying energetic particles that interact with the ambient particles is...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-04-01
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| Series: | Atoms |
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| Online Access: | https://www.mdpi.com/2218-2004/8/2/14 |
| _version_ | 1797570061453492224 |
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| author | Nat Gopalswamy |
| author_facet | Nat Gopalswamy |
| author_sort | Nat Gopalswamy |
| collection | DOAJ |
| description | Positrons play a major role in the emission of solar gamma-rays at energies from a few hundred keV to >1 GeV. Although the processes leading to positron production in the solar atmosphere are well known, the origin of the underlying energetic particles that interact with the ambient particles is poorly understood. With the aim of understanding the full gamma-ray spectrum of the Sun, I review the key emission mechanisms that contribute to the observed gamma-ray spectrum, focusing on the ones involving positrons. In particular, I review the processes involved in the 0.511 MeV positron annihilation line and the positronium continuum emissions at low energies, and the pion continuum emission at high energies in solar eruptions. It is thought that particles accelerated at the flare reconnection and at the shock driven by coronal mass ejections are responsible for the observed gamma-ray features. Based on some recent developments I suggest that energetic particles from both mechanisms may contribute to the observed gamma-ray spectrum in the impulsive phase, while the shock mechanism is responsible for the extended phase. |
| first_indexed | 2024-03-10T20:19:44Z |
| format | Article |
| id | doaj.art-defe34143a3f4498bc22f4335808d78c |
| institution | Directory Open Access Journal |
| issn | 2218-2004 |
| language | English |
| last_indexed | 2024-03-10T20:19:44Z |
| publishDate | 2020-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atoms |
| spelling | doaj.art-defe34143a3f4498bc22f4335808d78c2023-11-19T22:20:07ZengMDPI AGAtoms2218-20042020-04-01821410.3390/atoms8020014Positron Processes in the SunNat Gopalswamy0Solar Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAPositrons play a major role in the emission of solar gamma-rays at energies from a few hundred keV to >1 GeV. Although the processes leading to positron production in the solar atmosphere are well known, the origin of the underlying energetic particles that interact with the ambient particles is poorly understood. With the aim of understanding the full gamma-ray spectrum of the Sun, I review the key emission mechanisms that contribute to the observed gamma-ray spectrum, focusing on the ones involving positrons. In particular, I review the processes involved in the 0.511 MeV positron annihilation line and the positronium continuum emissions at low energies, and the pion continuum emission at high energies in solar eruptions. It is thought that particles accelerated at the flare reconnection and at the shock driven by coronal mass ejections are responsible for the observed gamma-ray features. Based on some recent developments I suggest that energetic particles from both mechanisms may contribute to the observed gamma-ray spectrum in the impulsive phase, while the shock mechanism is responsible for the extended phase.https://www.mdpi.com/2218-2004/8/2/14solar flarescoronal mass ejectionsshockspositronspositroniumpositron annihilation |
| spellingShingle | Nat Gopalswamy Positron Processes in the Sun Atoms solar flares coronal mass ejections shocks positrons positronium positron annihilation |
| title | Positron Processes in the Sun |
| title_full | Positron Processes in the Sun |
| title_fullStr | Positron Processes in the Sun |
| title_full_unstemmed | Positron Processes in the Sun |
| title_short | Positron Processes in the Sun |
| title_sort | positron processes in the sun |
| topic | solar flares coronal mass ejections shocks positrons positronium positron annihilation |
| url | https://www.mdpi.com/2218-2004/8/2/14 |
| work_keys_str_mv | AT natgopalswamy positronprocessesinthesun |