# On the role of magnetosonic solitons in perpendicular collisionless shock reformation

## TL;DR

This paper proposes that magnetosonic solitons are fundamental to the process of perpendicular collisionless shock reformation, offering a new perspective on shock dynamics and particle acceleration mechanisms.

## Contribution

It introduces the novel idea that shock reformation results from magnetosonic soliton formation, growth, and transition to super-critical shocks, supported by simulation and observational consistency.

## Key findings

- Magnetosonic solitons match observed foot structures in shocks.
- The period of soliton evolution aligns with classical reformation cycles.
- Soliton properties provide insights into shock non-stationarity and particle acceleration.

## Abstract

The nature of the magnetic structure arising from ion specular reflection in shock compression studies is examined by means of 1d particle in cell simulations. Propagation speed, field profiles and supporting currents for this magnetic structure are shown to be consistent with a magnetosonic soliton. Coincidentally, this structure and its evolution are typical of foot structures observed in perpendicular shock reformation. To reconcile these two observations, we propose, for the first time, that shock reformation can be explained as the result of the formation, growth and subsequent transition to a super-critical shock of a magnetosonic soliton. This argument is further supported by the remarkable agreement found between the period of the soliton evolution cycle and classical reformation results. This new result suggests that the unique properties of solitons can be used to shed new light on the long-standing issue of shock non-stationarity and its role on particle acceleration.