On the transmission of turbulent structures across the Earth's Bow Shock

TL;DR

This study combines spacecraft data and simulations to investigate how turbulent magnetic structures are transmitted across Earth's bow shock, revealing increased magnetic helicity downstream due to compression effects.

Contribution

It provides new insights into the transmission of turbulence across collisionless shocks using combined observational and simulation approaches.

Findings

Magnetic helicity increases downstream of the shock.

Turbulent structures are compressed at the shock front.

Simulation results confirm observational findings.

Abstract

Collisionless shocks and plasma turbulence are crucial ingredients for a broad range of astrophysical systems. The shock-turbulence interaction, and in particular the transmission of fully developed turbulence across the quasi-perpendicular Earth's bow shock, is here addressed using a combination of spacecraft observations and local numerical simulations. An alignment between the Wind (upstream) and MMS (downstream) spacecraft is used to study the transmission of turbulent structures across the shock, revealing an increase of their magnetic helicity content in its downstream. Local kinetic simulations, in which the dynamics of turbulent structures is followed through their transmission across a perpendicular shock, confirm this scenario, revealing that the observed magnetic helicity increase is associated with the compression of turbulent structures at the shock front.