Acceleration of Thermal Protons By Generic Phenomenological Mechanisms

Abstract

We investigate heating and acceleration of protons from a thermal gas with a generic diffusion and acceleration model, and subject to Coulomb scattering and energy loss, as was carried out in Petrosian & East (2008) for electrons. As protons gain energy their loss to electrons becomes important. Thus, we need to solve the coupled proton-electron kinetic equation. We numerically solve the coupled Fokker-Plank equations and computes the time evolution of the spectra of both particles. We show that this can lead to a quasi-thermal component plus a high energy nonthermal tail. We determine the evolution of nonthermal tail and the quasi-thermal component. The results may be used to explore the possibility of inverse bremsstrahlung radiation as a source of hard X-ray emissions from hot sources such as solar flares, accretion disk coronas and the intracluster medium of galaxy clusters. We find that emergence of nonthermal protons is accompanied by excessive heating of the entire plasma, unless the turbulence needed for scattering and acceleration is steeper than Kolmogorov and the acceleration parameters, the duration of the acceleration, and/or the initial distributions are significantly fine-tuned. These results severely constraint the feasibility of nonthermal inverse bremsstrahlung process producing hard X-ray emissions. However the nonthermal tail may be the seed particles for further re-acceleration to relativistic energies, say by a shock. In the Appendix we present some tests of the integrity of the algorithm used and present a new formula for the energy loss rate due to inelastic proton-proton interactions.

21 pages, 9 figures, accepted for publication in ApJ

References in corpus (8)

• Particle acceleration mechanisms
• Nonthermal phenomena in clusters of galaxies
• Nonthermal radiation mechanisms
• A NuSTAR observation of the center of the Coma Cluster
• Soft X-ray and extreme ultraviolet excess emission from clusters of galaxies
• Injection of $\kappa$-like Suprathermal Particles into Diffusive Shock Acceleration
• Evidence of thermonuclear flame spreading on neutron stars from burst rise oscillations
• Clusters of galaxies: beyond the thermal view

Cited by in corpus (4)

• Relativistic protons in the Coma galaxy cluster: first gamma-ray constraints ever on turbulent reacceleration
• Particle Acceleration in Solar Flares and Associated CME Shocks
• The Relation Between Escape and Scattering Times of Energetic Particles in a Turbulent Magnetized Plasma: Application to Solar Flares
• Particle Reacceleration by Turbulence and Radio Constraints on Multi-Messenger High-Energy Emission from the Coma Cluster