In time-distance helioseismology, wave travel times are measured from the cross-correlation between Doppler velocities recorded at any two locations on the solar surface. However, one of the main uncertainties associated with such measurements is how to interpret observations made in regions of strong magnetic field. Isolating the effects of the magnetic field from thermal or soundspeed perturb...

A partial decrease of the convective energy by the magnetic field of a sunspot causes the temperature of the magnetized plasma to decrease and this leads to a magneto-hydrostatic equilibrium. Thus, we expect a strong relation between magnetic field strength of a sunspot and its temperature/brightness. Here, we investigate this relation in the umbra of the large sunspot in NOAA10930 using spectr...

By inter-comparing exhaustively the results of wavelet analysis of the sunspot cycles and apparently associated oscillations in the time series of the zonal winds over the tropics, we found convincing evidences of the frequency shift of the oscillations, especially in the lower troposphere. The frequency of the oscillations forced by sunspot cycle decreased considerably in the lower troposphere...