MHD Shock-Clump Evolution with Self-Contained Magnetic Fields

TL;DR

This study investigates how magnetized clumps with self-contained magnetic fields interact with shock waves, revealing that magnetic field orientation and strength significantly influence clump evolution, turbulence, and observable morphology.

Contribution

It introduces the analysis of shock interactions with self-contained magnetic fields within clumps, a scenario previously less explored, and provides insights into magnetic influence on shock dynamics.

Findings

Clump evolution depends on magnetic field orientation relative to shock normal.

Magnetic pressure and tension influence post-shock behavior.

Morphology can indicate internal magnetic field topology.

Abstract

We study the interaction of strong shock waves with magnetized clumps. Previous numerical work focused on the simplified scenario in which shocked clumps are immersed in a globally uniform magnetic field that extends through both the clump and the ambient medium. Here we consider the complementary circumstance in which the field is completely self-contained within the clumps. This could arise naturally during clump formation via dynamical or thermal instabilities for example as magnetic field pinches off from the ambient medium. Using our AMR MHD code AstroBEAR, we carry out a series of simulations with magnetized clumps that have different self-contained magnetic field configurations. We find that the clump and magnetic evolution are sensitive to the fraction of magnetic field aligned with versus perpendicular to the shock normal. The relative strength of magnetic pressure and tension in the different field configurations allows us to analytically understand the different cases of post-shock evolution. We also show how turbulence and the mixing it implies depends of the initial field configuration and suggest ways in which observed shock-clump morphology may be used as a proxy for identifying internal field topologies a posteriori.