Magnetic loading of magnetars' flares

TL;DR

This paper shows that magnetic flux conservation governs magnetar flare dynamics, emphasizing magnetic energy redistribution over shock formation, which challenges traditional hydrodynamic models of such explosive events.

Contribution

It introduces a magnetic flux conservation framework for understanding magnetar flares, highlighting the dominance of magnetic energy stretching over shock-driven processes.

Findings

Magnetic flux conservation dominates flare dynamics.

Most energy is used to stretch magnetic fields, not do $pdV$ work.

Flares are balanced with pre-existing winds and do not produce strong shocks.

Abstract

Magnetars, the likely sources of Fast Radio Bursts (FRBs), produce both steady highly relativistic magnetized winds, and occasional ejection events. We demonstrate that the requirement of conservation of the magnetic flux dominates the overall dynamics of magnetic explosions. This is missed in conventional hydrodynamic models of the ejections as expanding shell with parametrically added magnetic field, as well as one-dimensional models of magnetic disturbances. Most of the initial free energy of an explosion is actually spent on stretching its own internal magnetic field, while doing minimal $pdV$ work against the surrounding. Magnetic explosions from magnetars come into force balance with the pre-flares wind close to the light cylinder. They are then advected quietly with the wind, or propagate as electromagnetic disturbances. No powerful shock waves are generated in the wind.