Relativistic Magnetohydrodynamic Simulations of Giant Magnetar Bursts

TL;DR

This paper presents the first relativistic magnetohydrodynamic simulations of magnetar eruptions, revealing how magnetic reconnection powers giant flares, ejects hot plasma, and potentially links to fast radio bursts.

Contribution

It introduces a novel simulation framework capturing the dynamics of magnetar eruptions, reconnection, and plasma ejection, providing insights into flare energetics and associated phenomena.

Findings

Reconnection-driven plasma heating and ejection of relativistically hot plasma.

Formation of a confined hot fireball explaining flare tails.

Ejection of a giant plasmoid carrying up to 9% of magnetic energy.

Abstract

Gradual crustal deformation can generate strongly twisted magnetic fields around magnetars, potentially triggering giant flares with total energies exceeding $10^{44}\,\mathrm{erg}$. In this Letter, we present the first relativistic magnetohydrodynamic simulation of a surface shear-driven magnetar eruption, capturing reconnection-driven plasma heating, the ejection of relativistically hot plasma, and the formation of a hot fireball confined within the inner magnetosphere. We find that magnetic reconnection in the equatorial current sheet launches a hot trailing outflow capable of powering the initial spike observed in giant flares, while simultaneously leaving behind a thermally stratified fireball with sufficient thermal energy to produce the pulsating, decaying tail. Together, these features provide a self-consistent physical framework for understanding the observed energetics of magnetar giant flares. The eruption also expels a magnetically dominated giant plasmoid carrying up to $\sim 9\%$ of the magnetosphere's total magnetic energy. Furthermore, our simulation demonstrates how the plasmoid drives the formation of a blast wave -- an important ingredient in models linking magnetar eruptions to fast radio bursts.