paper

Relativistic Magnetohydrodynamic Simulations of Giant Magnetar Bursts

arXiv:2602.17755 · doi:10.3847/2041-8213/ae8997

Abstract

Gradual crustal deformation can generate strongly twisted magnetic fields around magnetars, potentially triggering giant flares with total energies exceeding . 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 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.

arXiv commentApJL accepted version

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