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Gamma-Ray Emissions from Cosmic-Ray Interactions in Solar Magnetic Flux Tubes

Presentation #402.01 in the session Particle Interactions Throughout the Heliosphere.

Published onSep 18, 2023
Gamma-Ray Emissions from Cosmic-Ray Interactions in Solar Magnetic Flux Tubes

The Sun emits gamma rays ranging from several hundred MeV to 1 TeV through hadronic cosmic ray interactions with the solar atmosphere. A critical factor influencing this phenomenon is the reflection of cosmic rays by solar magnetic fields in the photosphere and the upper convection zone. In this talk, I will present a simplified solar magnetic flux tube structure that combines network elements and granular sheets, which serve as sites for gamma-ray emissions from hadronic cosmic-ray showers. Our findings reveal a gamma-ray spectrum, including the spectral index and overall magnitude, that aligns well with Fermi-LAT data at 1-200 GeV and HAWC at 1 TeV. I will demonstrate that the low-energy (less than 10 GeV) gamma rays are primarily produced in the network elements and high-energy (greater than 10 GeV) gamma rays in the granule sheets. Notably, I will show that the considerably softer gamma-ray spectrum at 1 TeV reported by HAWC results from the limited effectiveness of capturing and reflecting the highest energy (approximately 10 TeV) cosmic rays by finite-sized granular sheets. Lastly, I propose that solar gamma-ray observations offer a novel means to probe small-scale magnetic fields in the quiet Sun.

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