Magnetars are bursting neutron stars with ultrastrong magnetic fields. Their magnetospheric plasma is extreme in a few ways. Magnetic energy strongly dominates over the plasma rest mass, so magnetohydrodynamic (MHD) waves propagate with nearly speed of light. Dense (X-ray) radiation around the star strongly affects the plasma behavior – photons create the plasma itself, and radiative processes generate a drag on particle motions. A canonical problem of magnetar physics is how the magnetospheric plasma responds to a kHz perturbation from a star quake. Observationally, such events are associated with powerful X-ray bursts, the main form of magnetar activity. Furthermore, this activity is linked to fast radio bursts of enormous strength. Magnetospheric perturbations responsible for these phenomena can be shear Alfvén waves or compressive (fast magnetosonic) waves. Both can be modeled from first principles, using relativistic MHD and kinetic descriptions. This work investigates the plasma response to the waves, how the waves energize particles and launch relativistic explosions, and how the accompanying radiative processes can produce powerful X-ray and radio emission. Similar physics may occur in binary neutron stars, generating quasi-periodic bursting activity before the binary merges.
A Thu, study studied this question.