Physics
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmsh54a..02p&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #SH54A-02
Physics
7522 Helioseismology
Scientific paper
Studying of propagation, conversion, and scattering of MHD waves in the Sun is very important for developing robust local helioseismology techniques and diagnostics of subsurface magnetic fields. We use 3D numerical simulations to study propagation of MHD waves from wave sources of different types (vertical force and pressure) in presence of uniform and non-uniform inclined magnetic field, and for an equilibrium sunspot model. Numerical simulations show that presence of the background magnetic field significantly alters properties of the surface gravity f-modes, but has substantially smaller effect on p-modes. When the wave source is located in a strong field region it generates Alfven waves. The Alfven waves do not appear if the wave source is located in the region without magnetic field, and waves propagate from that region into the region with magnetic field without significant transformation. The wave travel times obtained from cross covariance of the p-mode line-of-sight velocities at the observation point and the source point show variation of about 1 min along the wave front. Due to asymmetry, average of travel times along the wave front is not zero and show variations of about a few seconds. Comparison of the simulations with the time-distance helioseismology results from SOHO/MDI shows that the observed variations of acoustic travel times obtained from the Doppler velocity measurements are not caused by the inclined magnetic field effects contrary to previous suggestions.
Kosovichev Aleksandr G.
Parchevsky Konstantin V.
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