# Observations of Magnetic Reconnection in the Transition Region of Quasi-Parallel Shocks

## TL;DR

This paper reports the first direct observations of electron-only magnetic reconnection within Earth's quasi-parallel bow shock transition layer, highlighting electron heating effects without ion involvement.

## Contribution

It provides the first observational evidence of electron-only reconnection in shock transition regions, supported by MMS data and consistent with simulation predictions.

## Key findings

- Electron jets and heating observed at current sheets
- No ion response detected during reconnection events
- Reconnection occurs on sub-ion timescales

## Abstract

Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi-parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron-only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub-ion timescales. We also discuss the impact of electron heating in shocks via reconnection.