How well do the oscillation frequencies track the activity ?
S. C. Tripathy, John. W. Leibacher
National Solar Observatory, 950 N Cherry Avenue, Tucson 85719, USA
Variations of solar oscillation frequencies with the solar cycle at
both low and intermediate degrees are now well established. This is
manifested by an increase in frequencies of the modes from minimum to
maximum of the activity cycle. It is also known that the shifts are
strongly correlatd with different activity indices on time scales of 72
and 108 days for MDI and GONG data respectively. However, earlier
results from cycle 22 indicated that the frequencies change over
shorter periods of weeks to months. It is therefore interesting to
analyse mode frequencies and other mode parameters from time series of
shorter duration. Here, we present results from an analysis where the
frequencies are computed from 36 and 108 days long time series; the
time series being shifted by three days over a period of about 5
months. The frequencies calculated from the 36 day long time series are
much better correlated with the activity indices.