Sheared Flow As A Stabilizing Mechanism In Astrophysical Jets

TL;DR

This paper hypothesizes that sheared helical flow can stabilize current-driven instabilities in astrophysical jets, potentially explaining their observed narrowness and magnetic collimation.

Contribution

It introduces the novel idea that sheared helical flow may stabilize instabilities in YSO jets, extending plasma stability concepts to astrophysical phenomena.

Findings

Sheared flow reduces growth rates of instabilities in magnetized plasmas.

Analytical and numerical evidence supports the stabilizing effect of sheared flow.

Potential explanation for the narrow, collimated structure of astrophysical jets.

Abstract

It has been hypothesized that the sustained narrowness observed in the asymptotic cylindrical region of bipolar outflows from Young Stellar Objects (YSO) indicates that these jets are magnetically collimated. The j cross B force observed in z-pinch plasmas is a possible explanation for these observations. However, z-pinch plasmas are subject to current driven instabilities (CDI). The interest in using z-pinches for controlled nuclear fusion has lead to an extensive theory of the stability of magnetically confined plasmas. Analytical, numerical, and experimental evidence from this field suggest that sheared flow in magnetized plasmas can reduce the growth rates of the sausage and kink instabilities. Here we propose the hypothesis that sheared helical flow can exert a similar stabilizing influence on CDI in YSO jets.