Magnetar Oscillations I: strongly coupled dynamics of the crust and the core

Understand

Quasi-Periodic Oscillations (QPOs) observed during Soft Gamma Repeaters giant flares are commonly interpreted as the torsional oscillations of magnetars.

• The oscillatory motion is influenced by the strong interaction between the shear modes of the crust and Alfven-like modes in the core.
• We study the dynamics which arises through this interaction, and present several new results: (1) We show that global {\it edge modes} frequently reside near the edges of the core Alfven continuum.
• (2) We compute the magnetar's oscillatory motion for realistic axisymmetric magnetic field configurations and core density profiles, but with a simplified model of the elastic crust.