Poster abstract details

Spatial variations in surface acoustic power are most evident in the presence of surface magnetic fields. In addition to this, the power varies with frequency. The reason for this is not, as yet, clear. Here we show newly discovered properties of the enhanced acoustic power observed near disk center from 21 to 27 January 2002, including AR 9787. We find (i) a strong correlation of the enhanced high frequency power with horizontal magnetic-fields, (ii) the frequency of the maximum enhancement increases with magnetic field strength, and (iii) the oscillations contributing to the halos show modal ridges which are shifted to higher wavenumber at constant frequency in comparison to the ridges of waves in the quiet-Sun. These observations will help to discern the physical cause of the acoustic power variations.