Letter to the Editor

Comparing simulated and observed particle energy distributions through magnetic reconnection in Earth’s magnetotail

¹ Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven Leuven, Belgium
² Royal Belgian Institute for Space Aeronomy, Solar-Terrestrial Centre of Excellence Uccle, Belgium

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 15 December 2025
Accepted: 23 January 2026

Abstract

Context. Magnetic reconnection is an explosive process that accelerates particles to high energies in Earth’s magnetosphere, offering a unique natural laboratory to study this phenomenon.

Aims. This study investigates how well data-driven fully kinetic simulations can reproduce the ion and electron energy distributions observed during a reconnection event by the Magnetospheric Multiscale (MMS) mission.

Methods. We performed fully kinetic 2D simulations initialized with plasma parameters derived from the MMS event and compared the resulting ion and electron energy distributions with observations. Key numerical and physical parameters were systematically varied to assess their influence on the resulting particle spectra.

Results. The simulations capture the overall shape and evolution of nonthermal energy distributions for both species, but generally underestimate the very high-energy tail of the electron spectrum. Variations in numerical parameters have negligible effects on the resulting spectra, while the initial upstream temperatures instead play a more pronounced role in reproducing the observed distributions.

Conclusions. We present a novel analysis of data-driven fully kinetic simulations of MR, showing that key aspects of particle acceleration can be captured, while also highlighting the limitations of 2D simulations and the need for more realistic (e.g., 3D) setups to reproduce the observed particle energization accurately.