Energy Deposition by Cosmic Rays in the Molecular Cloud Using GEANT4 Code and Voyager I Data

Author(s)

Pazianotto, Mauricio Tizziani ^[1] ; Pilling, Sergio ^[2] ; Molina, Jose Manuel Quesada ^[3] ; Federico, Claudio Antonio ^[4]

Affiliation

^[1] Inst Tecnol Aeronaut, Sao Jose Dos Campos - Brazil

^[2] Univ Vale Paraiba, Sao Jose Dos Campos - Brazil

^[3] Univ Seville, Seville - Spain

^[4] Inst Adv Studies, Sao Jose Dos Campos - Brazil

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 911, n. 2 APR 2021.
• Web of Science Citations: 0

Abstract

Molecular clouds (MCs) are exposed to Galactic and extragalactic cosmic rays (CR) that trigger several physical and physicochemical changes, including gas and grain heating and molecular destruction and formation. Here we present a theoretical model describing the energy delivered by CRs, composed of protons, alphas, and electrons taken from Voyager I measurements, into a typical MC with 5400 M (composed mainly of H with a density law of r (-1.2)) and size around 1 x 10(6) au. The calculation was performed employing the Monte Carlo toolkit GEANT4 to obtain the energy deposition per mass from several types of secondary particles (considering nuclear and hadron physics). The results indicate that incoming protons contribute to most of the energy delivered in the MC in all regions (maximum similar to 230 MeV g(-1) s(-1) at outer regions of the cloud). Secondary electrons are the second most important component for energy deposition in almost all layers of the MC and can deliver an energy rate of similar to 130 MeV g(-1) s(-1) in the outer region of the MC. Other cascade particles have their major energy delivery in the central and denser core of the MC. From a temperature model (considering CR data from Voyager I), we observed (i) a small bump in temperature at the distance of 3 x 10(3)-2 x 10(4) au from the center, (ii) a rapid temperature decrease (roughly 7 K) between the outer layer and the second most outer layer, and (iii) that, at a distance of 5 x 10(4) au (Av > 10), the gas temperature of the MC is below 15 K. (AU)

• FAPESP's process: 19/13577-0 - Computational platform for simulation of cosmic radiation in the aeronautical environment
• Grantee: Maurício Tizziani Pazianotto
• Support Opportunities: Regular Research Grants