Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields

Abstract

Cosmic rays can interact with the solar atmosphere and produce a slew of secondary messengers, making the Sun a bright gamma-ray source in the sky. Detailed observations with Fermi-LAT have shown that these interactions must be strongly affected by solar magnetic fields in order to produce the wide range of observational features, such as high flux and hard spectrum. However, the detailed mechanisms behind these features are still a mystery. In this work, we tackle this problem by performing particle interaction simulations in the solar atmosphere in the presence of coronal magnetic fields modelled using the potential field source surface (PFSS) model. We find that the low-energy (~GeV) gamma-ray production is significantly enhanced by the coronal magnetic fields, but the enhancement decreases rapidly with energy. The enhancement is directly correlated with the production of gamma rays with large deviation angles relative to the input cosmic-ray direction. We conclude that coronal magnetic fields are essential for correctly modeling solar disk gamma rays below 10GeV, but above that the effect of coronal magnetic fields diminishes. Other magnetic field structures are needed to explain the high-energy disk emission.

References in corpus (8)

• Global maps of the magnetic field in the solar corona
• Fermi-LAT Observations of Two Gamma-Ray Emission Components from the Quiescent Sun
• Gamma-ray emission from the solar halo and disk: a study with EGRET data
• Dark matter in the solar system II: WIMP annihilation rates in the Sun
• Search for dark matter signatures in the gamma-ray emission towards the Sun with the Fermi Large Area Telescope
• A search for dark matter cosmic-ray electrons and positrons from the Sun with the Fermi Large Area Telescope
• High energy neutrinos from the Sun
• Evaluation of the Interplanetary Magnetic Field Strength Using the Cosmic-Ray Shadow of the Sun

Cited by in corpus (1)

• A study of super-luminous stars with the Fermi Large Area Telescope