FLUKA Simulations of Pion Decay Gamma-Radiation from Energetic Flare Ions

Author(s)

MacKinnon, Alexander ^[1] ; Szpigel, Sergio ^[2] ; Gimenez de Castro, Guillermo ^{[2, 3]} ; Tuneu, Jordi ^[2]

Affiliation

^[1] Univ Glasgow, Sch Phys & Astron, Glasgow G12 8QQ, Lanark - Scotland

^[2] Univ Presbiteriana Mackenzie, Ctr Radio Astron & Astrofis Mackenzie, Sao Paulo - Brazil

^[3] UBA CONICET, Inst Astron & Fis Espacio, Buenos Aires, DF - Argentina

• Document type: Journal article
• Source: SOLAR PHYSICS; v. 295, n. 12 DEC 8 2020.
• Web of Science Citations: 0

Abstract

Gamma-ray continuum at > 10 MeV photon energy yields information on greater than or similar to 0.2-0.3 GeV/nucleon ions at the Sun. We use the general-purpose Monte Carlo code FLUktuierenden KAskade (FLUKA) to model the transport of ions injected into thick and thin target sources, the nuclear processes that give rise to pions and other secondaries and the escape of the resulting photons from the atmosphere. We give examples of photon spectra calculated with a range of different assumptions about the primary ion velocity distribution and the source region. We show that FLUKA gives results for pion decay photon emissivity in agreement with previous treatments. Through the directionality of secondary products, as well as Compton scattering and pair production of photons prior to escaping the Sun, the predicted spectrum depends significantly on the viewing angle. Details of the photon spectrum in the approximate to 100 MeV range may constrain the angular distribution of primary ions and the depths at which they interact. We display a set of thick-target spectra produced making various assumptions about the incident ion energy and angular distribution and the viewing angle. If ions are very strongly beamed downward, or ion energies do not extend much above 1 GeV/nucleon, the photon spectrum is highly insensitive to details of the ion distribution. Under the simplest assumptions, flares observed near disc centre should not display significant radiation above 1 GeV photon energy. We give an example application to Fermi Large Area Telescope data from the flare of 12 June 2010. (AU)

• FAPESP's process: 17/13282-5 - Modelling of nuclear processes in solar flares using Monte Carlo simulation packages
• Grantee: Sérgio Szpigel
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/18386-7 - Integrated modelling of radio and X-ray emission during solar flares
• Grantee: Carlos Guillermo Giménez de Castro
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/24155-3 - Solar flare diagnostic in an unprecedented frequency range from microwaves to THz frequencies: challenges for interpretation (flat)
• Grantee: Carlos Guillermo Giménez de Castro
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/23428-4 - Monte Carlo simulations of nuclear processes during solar flares in magneto-active plasmas
• Grantee: Jordi Tuneu Serra
• Support Opportunities: Scholarships in Brazil - Doctorate