On the power and frequency of p-modes in sunspots

Abstract

A time series of GONG Dopplergrams has been used to measure the velocity fluctuations in the sunspot and quiet photosphere simultaneously. The power spectrum analysis shows that the power of the predominant p-mode is reduced in the sunspot region by 36 to 51% as compared to the quiet photosphere. Our results also show a relative frequency shift of the power envelope of these modes of the order of 70 to 300 ?Hz.