HR: 0830h
AN: SP11B-02    [Abstracts]
TI: Effect of phase speed filters on time-distance correlations of acoustic waves on the Sun.
AU: * Nigam, R
EM: rakesh@quake.stanford.edu
AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, 445 Via Palou, Stanford, CA 94305 United States
AU: Rajaguru, P
EM: rajaguru@stanford.edu
AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, 445 Via Palou, Stanford, CA 94305 United States
AU: Kosovichev, A G
EM: sasha@quake.stanford.edu
AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, 445 Via Palou, Stanford, CA 94305 United States
AB: Use of phase-speed filters in time-distance helioseismic measurements is crucial to obtain spatially resolved information about localised sub-surface structures. These filters have to be chosen such that the travel times of the waves that are filtered in are themselves not affected by the filtering process. Here we derive analytically the cross-correlation signal that results from phase-speed filtered signals, assuming plane wave conditions. The resulting wavelet explicitly depends on the parameters of the filters, such as the phase-speed and its dispersion, in contrast to the currently used Gabor wavelet, and hence accounts for any filter induced changes in travel times. Alternatively, this new wavelet allows the determination of optimum parameters for the filters.
DE: 7522 Helioseismology
DE: 7524 Magnetic fields
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly