SHORT-TERM CHANGES IN SOLAR OSCILLATION FREQUENCIES AND SOLAR-ACTIVITY

We show that the frequencies of solar p-mode oscillations change significantly over periods as short as 1 month. These changes correlate significantly with variations in the strength of surface solar activity as measured by the average, over the Sun's visible surface, of the magnitude of the line-of-sight magnetic field component from magnetograms. The frequency and mean magnetic variations are found to obey a linear relationship. We find that the mean frequency shift at any time depends on the history of solar activity over an interval of, at most, several months prior to the measurement and conclude that the dominant mechanism of the frequency shift is correlated with surface magnetic activity.