Local Frequency Shifts
The frequencies of local modes, as determined by ring diagram analysis, have been shown to increase with local magnetic activity level (Hindman et al., 2000). The 29 1664-minute 'days' of GONG+ ring diagram data were analyzed for this effect, sing the Kitt Peak synoptic magnetic data for comparison. The frequency estimates for each mode were first arranged in a synoptic chart. A linear regression was then carried out using the gross magnetic flux B as the independent variable and the frequency as the dependent variable, to obtain a zero-flux frequency estimate and a sensitivity value snld nu/dB. The figure below left shows a sample regression result. Below right, we plot the sensitivity, scaled by the normalized mode inertia, as a function of frequency, with the ridges color-coded by radial degree. The corresponding results from global modes (Howe et al. 2002) are shown as points with error bars.
