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Electron Heating by Kinetic Alfvén Waves in Coronal Loop Turbulence

Abstract:

A test-particle model describing the energization of electrons in a turbulent plasma is presented. Parameters are chosen to represent turbulence in a magnetic structure of the solar corona. A fluctuating electric field component parallel to the background magnetic field, with properties similar to those of Kinetic Alfvén Waves, is assumed to be present at scales of the order of the proton Larmor radius. Electrons are stochastically accelerated by multiple interactions with such fluctuations, reaching energies of the order of 10 2 eV within tens to hundreds of seconds, depending on the turbulence amplitude. For values of the large-scale plasma velocity fluctuation of the order of tens of kilometers per second, the power absorbed by electrons per surface unit is of the order of that typically necessary to heat the corona. The power that electrons absorb from fluctuations is proportional to the third power of the large-scale velocity amplitude, and is comparable with the power associated with the turbulent cascade. Therefore, this mechanism can be considered as an equivalent kinetic dissipation for turbulence, and it can play a relevant role in the heating of electrons in the corona.