# Self-similar structure of ultra-relativistic magnetized termination shocks and the role of reconnection in long-lasting GRB ouflows

## TL;DR

This paper analyzes the structure of ultra-relativistic magnetized shocks in gamma-ray burst (GRB) outflows, highlighting the role of magnetic reconnection in particle acceleration and emission processes.

## Contribution

It introduces a detailed model of the double-shock structure with a focus on magnetic reconnection at the contact discontinuity in GRB flows.

## Key findings

- Magnetic field amplification creates a narrow magnetosheath at the contact discontinuity.
- Magnetic reconnection in the post-reverse shock region can accelerate particles responsible for X-ray and GeV emissions.
- The contact discontinuity acts as an Alfven tangential discontinuity with non-analytic properties.

## Abstract

We consider the double-shock structure of ultra-relativistic flows produced by the interaction of magnetized wind with magnetized external medium. The contact discontinuity (CD) is a special point in the flow - density, kinetic pressure and magnetic field experience a jump or are non-analytic on the CD. To connect dynamically the outside region (the forward shock flow) with the inside region (the reverse shock flow) requires resolving flow singularities at the contact discontinuity. On the CD the pressure is communicated exclusively by the magnetic field on both sides - the CD becomes an Alfven tangential discontinuity. Thus, the dynamic amplification of the magnetic field leads to a formation of a narrow magnetosheath. We discussed a possibility that particles emitting early $X$-ray afterglows, as well as Fermi GeV photons, are accelerated via magnetic reconnection processes in the post-reverse shock region, and in the magnetosheath in particular.