Spontaneous Magnetic Fluctuations of Kappa Electron Distributions

Abstract:

In situ measurement of particle distributions in space plasmas usually exhibit a variety of non-equilibrium features in the form of temperature anisotropy, suprathermal tails, and field-aligned beams, among others. The departure from thermal equilibrium provides a source for spontaneous emissions of electromagnetic fluctuations, such as whistler-cyclotron fluctuations at the electron scales. Analysis of these fluctuations provides relevant information about the plasma state and its macroscopic properties. By comparing 1.5D PIC simulations of a finite temperature magnetized electron-proton plasma loaded with Maxwellian and generalized kappa velocity distributions, we found new insights of the wave-particle interaction behavior, suggesting a strong dependence between the shape of the velocity distribution function and the spontaneous magnetic fluctuations wave spectrum. This feature may be used as a proxy to identify the nature of electron populations in space plasmas at locations where direct measurements of particle fluxes are not available.

Acknowledgement: these results were obtained in the framework of the projects SCHL 201/35-1 (DFG-German Research Foundation), GOA/2015-014 (KU Leuven), G0A2316N (FWO- Vlaanderen), C~90347 (ESA Prodex 9), and Fondecyt No. 1191351 (ANID, Chile). P.S.M is grateful for the support of KU Leuven BOF Network Fellowship NF/19/001.