Role of magnetic arcades in explaining the puzzle of the gamma-ray emission from the solar disk
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arXiv
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| Format: | Preprint |
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2024
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| author | Puzzoni, Eleonora Fraschetti, Federico Kóta, József Giacalone, Joe |
| author_facet | Puzzoni, Eleonora Fraschetti, Federico Kóta, József Giacalone, Joe |
| contents | The interpretation of gamma-ray emission originating from the solar disk ($0.5^\circ$ in angular size) as due to the interaction of Galactic Cosmic Rays (GCRs) with the solar atmosphere has remained a central challenge in solar physics. After the seminal work by Seckel, Stanev, and Gaisser (SSG91) based on GCRs magnetic mirroring, discrepancies between models and observations persist, indicating the need for a novel approach. The present work focuses on exploring the impact of a closed magnetic field geometry in the low photosphere on the observed gamma-ray flux. We track numerically with the PLUTO code the trajectories of test-particle protons within a static $\sim 20$ Mm scale height magnetic arcade adjacent to jets. By making use of numerical vertical density profiles we inject particles at distinct chromospheric/photospheric altitudes, mimicking the migration of GCRs from neighboring flux tubes into closed arcades. Remarkably, our model reproduces a flat gamma-ray spectrum below $\sim 33$ GeV, a nearly-isotropic emission at $\sim 10$ GeV, both consistent with Fermi-LAT observations, and a near-limb emission at $\sim 1$ TeV. Our model can also reproduce the flux-drop detected by HAWC ($\sim 1$ TeV). Finally, we argue that the spectral dip observed at $\sim$ 40 GeV may result from the flux suppression at low energy due to the cross-field diffusion, which would produce a cutoff. These findings underscore the pivotal role of closed magnetic field structures in shaping the solar disk gamma-ray emission. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_16859 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Role of magnetic arcades in explaining the puzzle of the gamma-ray emission from the solar disk Puzzoni, Eleonora Fraschetti, Federico Kóta, József Giacalone, Joe High Energy Astrophysical Phenomena Solar and Stellar Astrophysics The interpretation of gamma-ray emission originating from the solar disk ($0.5^\circ$ in angular size) as due to the interaction of Galactic Cosmic Rays (GCRs) with the solar atmosphere has remained a central challenge in solar physics. After the seminal work by Seckel, Stanev, and Gaisser (SSG91) based on GCRs magnetic mirroring, discrepancies between models and observations persist, indicating the need for a novel approach. The present work focuses on exploring the impact of a closed magnetic field geometry in the low photosphere on the observed gamma-ray flux. We track numerically with the PLUTO code the trajectories of test-particle protons within a static $\sim 20$ Mm scale height magnetic arcade adjacent to jets. By making use of numerical vertical density profiles we inject particles at distinct chromospheric/photospheric altitudes, mimicking the migration of GCRs from neighboring flux tubes into closed arcades. Remarkably, our model reproduces a flat gamma-ray spectrum below $\sim 33$ GeV, a nearly-isotropic emission at $\sim 10$ GeV, both consistent with Fermi-LAT observations, and a near-limb emission at $\sim 1$ TeV. Our model can also reproduce the flux-drop detected by HAWC ($\sim 1$ TeV). Finally, we argue that the spectral dip observed at $\sim$ 40 GeV may result from the flux suppression at low energy due to the cross-field diffusion, which would produce a cutoff. These findings underscore the pivotal role of closed magnetic field structures in shaping the solar disk gamma-ray emission. |
| title | Role of magnetic arcades in explaining the puzzle of the gamma-ray emission from the solar disk |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2407.16859 |