Activity‐related Changes in Local Solar Acoustic Mode Parameters from Michelson Doppler Imager and Global Oscillations Network Group

Abstract

We use the ring-diagram technique of local helioseismology to study the amplitude and line width of high-degree solar acoustic modes from 474 days of data from the Michelson Doppler Imager Dynamics program, covering the period 1996-2002. The 2002 data are compared with contemporaneous data from the Global Oscillations Network Group network. The results, once instrumental effects have been removed, show a strong dependence of the amplitude and lifetime of the modes on the local magnetic flux, with the amplitude and lifetime decreasing in the 5 minute band and a reversed trend at high frequencies. We relate these findings to results from global modes and from other approaches for analyzing high-degree local oscillations.