A note on the experiment parameters for the non-resonant streaming instability: competition between left and right circularly polarized modes

TL;DR

This paper explores the parameters influencing the non-resonant streaming instability, focusing on polarization competition, to better understand magnetic turbulence relevant for cosmic-ray acceleration, through theoretical analysis and PIC simulations.

Contribution

It investigates the polarization effects and saturation mechanisms of the non-resonant streaming instability using theoretical analysis and PIC simulations, tailored for laboratory experiments.

Findings

Right-handed mode growth rate may be smaller than left-handed mode

Left-handed resonant mode can be ignored due to longer wavelength

PIC simulations support the occurrence of non-resonant streaming instability

Abstract

A non-resonant streaming instability driven by cosmic-ray currents, also called Bell's instability, is proposed as a candidate for providing the required magnetic turbulence of efficient diffusive shock accelerations. To demonstrate the saturation level and mechanism of the non-resonant streaming instability in a laboratory environment, we attempt to develop an experiment at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). As an electron beam is used to replace the proton beam to carry the cosmic-ray current in our experiment, the polarization of the non-resonant streaming instability will be modified from the left-handed (LH) mode to the right-handed (RH) mode. The theoretical instability analysis shows that the growth rate of this RH non-resonant mode may be smaller than it of the LH resonant mode. However the LH resonant mode can be ignored in our experiment while the expected wavelength is longer than the used plasma cell. The results of PIC simulations will also support this contention and the occurrence of non-resonant streaming instability in our experiment.