# Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

## TL;DR

This paper explores how strong magnetic guide fields enable electron cyclotron maser instability (ECMI) during magnetic reconnection, leading to electromagnetic emissions relevant for space and astrophysical phenomena.

## Contribution

It introduces a mechanism for ECMI in strong guide fields during reconnection, highlighting asymmetries and potential applications in space physics and astrophysics.

## Key findings

- ECMI can be excited in strong guide field reconnection.
- Asymmetries in electron populations facilitate ECMI.
- Potential applications include auroral kilometric radiation and solar radio emissions.

## Abstract

Reconnection in strong current-aligned magnetic guide fields allows for the excitation of the electron-cyclotron-maser instability and emission of electromagnetic radiationfrom the electron exhaust at the {\sf X} point. The electrons in the guide field remain magnetized, with reconnection barely affected. The guide field is responsible for the asymmetric properties of the {\sf X} point and exhaust. Asymmetry in the electron population results in conditions favorable for ECMI. Fundamental mission beneath the guide field cyclotron is similar to electron hole emission discussed elsewhere. It can be treated in the proper exhaust frame, and maps the local magnetic field when moving together with the exhaust along the guide field. Many applications of this mechanism can be imagined. We propose an outline of the mechanism and discuss some of its advantages and prospects. Among potential applications are AKR in auroral physics, various types of solar radio emissions during flares, planetary emissions and several astrophysical scenarios involving the presence of strong fields and field-aligned currents. Escape of radiation from {\sf X} is no problem. However, observation from remote requires traversing the stop-band of X modes and implies source displacements to weaker fields.