Oscillations of sunspot magnetic fields
Solanki, S. K.; Scherrer, P. H.; Stenflo, J. O.; Tarbell, T.; Rueedi, I.
Switzerland, United States
Abstract
We report on velocity and magnetic field oscillations observed in sunspots using the MDI instrument onboard SOHO. In addition to the well-known velocity oscillations, the data clearly show highly localised oscillations of the magnetogram signal in different parts of the sunspots. We show that only oscillations of the magnetic field vector can produce the observed magnetogram oscillations, and that the observed phase relations suggest an origin in terms of magnetoacoustic gravity waves.