Sunquakes

Sunquakes or starquakes are seismic events that occur on stars. They can be produced by solar flares and their corresponding coronal mass ejections. A starquake can also occur when the crust of a neutron star undergoes a sudden adjustment, an event that has been suggested is closely related to the giant gamma ray flares that are produced approximately once per decade from soft gamma repeaters.

Starquakes in neutron stars are thought to result from two different mechanisms. One is the huge stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior magnetic fields. A second cause is a result of spindown. As the neutron star loses angular momentum due to frame-dragging and by the bleeding off of energy due to it being a rotating magnetic dipole, the crust develops an enormous amount of stress. Once they exceed a certain amount, the shape adjusts itself to a shape closer to equilibrium, a perfect sphere. The actual change is believed to be on the order of micrometers or less, and occurs in less than a millionth of a second.

A large starquake was recorded on the ultracompact stellar corpse (magnetar) SGR 1806-20. It released gamma rays equivalent to 10³⁶ kW in intensity.

The study of sunquakes is called astroseismology.