Magnetic field amplification by collisionless shocks in partially ionized plasmas

TL;DR

This study uses hybrid simulations to analyze collisionless shocks in partially ionized plasmas, revealing large fluctuations and complex downstream atom velocity distributions, indicating potential for diffusive shock acceleration in such environments.

Contribution

It provides the first detailed simulation-based analysis of shock structures and particle distributions in partially ionized plasmas, highlighting the feasibility of shock acceleration mechanisms.

Findings

Large density and magnetic field fluctuations in upstream and downstream regions.

Downstream hydrogen atoms exhibit three velocity components.

Shock structures support the operation of diffusive shock acceleration.

Abstract

In this paper, we study shock structures of collisionless shocks in partially ionized plasmas by means of two-dimensional hybrid simulations, where the shock is a perpendicular shock with shock velocity Vsh ~ 40 Va ~ 1333 km/s and the upstream ionization fraction is 0.5. We find that large density fluctuations and large magnetic fields fluctuations are generated both in the upstream and downstream regions. In addition, we find that the velocity distribution of downstream hydrogen atoms has three components. Observed shock structures suggest that diffusive shock acceleration can operate at perpendicular shocks propagating into partially ionized plasmas in real three-dimensional systems.