On the growth of the thermally modified non-resonant streaming instability

TL;DR

This paper investigates how ambient plasma temperature affects the growth rate and magnetic field amplification of the non-resonant streaming instability driven by cosmic rays, using analytical models and hybrid-PIC simulations.

Contribution

It provides analytical expressions for the instability's growth rate in hot plasma and explores its non-linear evolution across different temperatures.

Findings

Higher plasma temperatures reduce the instability's growth rate.

In cold plasma, about two-thirds of cosmic ray energy converts into magnetic energy.

Temperature significantly influences the saturation level of magnetic fields.

Abstract

The cosmic rays non-resonant streaming instability is believed to be the source of substantial magnetic field amplification. In this work we investigate the effects of the ambient plasma temperature on the instability and derive analytical expressions of its growth rate in the hot, demagnetized regime of interaction. To study its non-linear evolution we perform hybrid-PIC simulations for a wide range of temperatures. We find that in the cold limit about two-thirds of the cosmic rays drift kinetic energy is converted into magnetic energy. Increasing the temperature of the ambient plasma can substantially reduce the growth rate and the magnitude of the saturated magnetic field.