Parametric instabilities of large-amplitude parallel propagating Alfven waves: 2-D PIC simulation

TL;DR

This study uses 2-D PIC simulations to analyze parametric instabilities of large-amplitude parallel Alfven waves, confirming electron and ion heating mechanisms and suggesting the dominant instability is the parallel decay instability.

Contribution

It provides new insights into the generation mechanisms of longitudinal waves and evaluates the significance of electron heating in large-amplitude Alfven wave interactions.

Findings

Electrons are heated mainly by the modified two-stream instability.

Ions are heated by parallel propagating ion acoustic waves.

The parallel decay instability is likely the primary mechanism for wave generation.

Abstract

We discuss the parametric instabilities of large-amplitude parallel propagating Alfven waves using the 2-D PIC simulation code. First, we confirmed the results in the past study [Sakai et al, 2005] that the electrons are heated due to the modified two stream instability and that the ions are heated by the parallel propagating ion acoustic waves. However, although the past study argued that such parallel propagating longitudinal waves are excited by transverse modulation of parent Alfven wave, we consider these waves are more likely to be generated by the usual, parallel decay instability. Further, we performed other simulation runs with different polarization of the parent Alfven waves or the different ion thermal velocity. Numerical results suggest that the electron heating by the modified two stream instability due to the large amplitude Alfven waves is unimportant with most parameter sets.