Interstellar Turbulent Magnetic Field Generation by Plasma Instabilities

TL;DR

This paper estimates the maximum magnetic field strength generated by plasma instabilities in the interstellar medium, showing micro Gauss fields can be produced under typical conditions and analyzing the effects of plasma parameters and ambient magnetic fields.

Contribution

It provides a detailed parameter study of plasma instabilities, identifying conditions for dominant instability modes and effects of ambient magnetic fields on magnetic field generation.

Findings

Micro Gauss magnetic fields can be generated by plasma instabilities.

The dominant instability depends on streaming velocity and plasma temperature.

Ambient magnetic fields suppress filamentation instability but not two-stream or Weibel instability.

Abstract

The maximum magnetic field strength generated by Weibel-type plasma instabilities is estimated for typical conditions in the interstellar medium. The relevant kinetic dispersion relations are evaluated by conducting a parameter study both for Maxwellian and for suprathermal particle distributions showing that micro Gauss magnetic fields can be generated. It is shown that, depending on the streaming velocity and the plasma temperatures, either the longitudinal or a transverse instability will be dominant. In the presence of an ambient magnetic field, the filamentation instability is typically suppressed while the two-stream and the classic Weibel instability are retained.