SOHO CoRoT Kepler Picard SDO GONG

Time-Distance Helioseismology with the HMI instrument


duvall thomas


NASA Goddard Space Flight Center


Local helioseismology


We expect considerable improvement of time-distance results from the HMI instrument as opposed to the earlier MDI and GONG data. The higher data rate makes possible several improvements, including faster temporal sampling (45 sec), smaller spatial pixels (0.5 arc sec), better wavelength coverage (6 samples across the line all transmitted to the ground), and year-round coverage of the full disk. The higher spatial resolution makes possible better longitude coverage of active regions and supergranulation and also better latitude coverage. Doppler, continuum, and line depth images have a strong granulation signal. Line core images show little granulation. Analyses to test the limits of these new capabilities will be presented.
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