# In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection

## TL;DR

This paper presents in situ spacecraft observations revealing that the electron diffusion region during magnetopause reconnection is structured and inhomogeneous, challenging the assumption of a uniform EDR.

## Contribution

The study provides the first direct multi-point measurements showing the inhomogeneous structure of the EDR during magnetopause reconnection.

## Key findings

- Evidence of inhomogeneous current densities within the EDR
- Energy conversion is patchy over electron inertial lengths
- Observations align with recent kinetic simulations

## Abstract

The Electron Diffusion Region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric MultiScale (MMS) novel spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multi-point measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations.