TRAVEL TIME MEASUREMENTS IN SUNSPOTS

摘要

Time-distance helioseismology is a powerful tool tornprobe the conditions of small structures below the sur-rnface of the Sun. One of the successful applications ofrnthis technique was developed by Duvall using South Polerndata. Using GONG data we investigate the travel timernchanges in sunspots. To increase the signal to noise ra-rntio, we applied a phase velocity u0002lter to the time series.rnPreliminary results show that decreasing of travel timesrnin sunspot regions depends on the signal that has beenrnused to compute cross-correlations. We present travelrntime measurements using different wave packets propa-rngating to different depths of the solar interior.rnWe present a list of sunspots that we have analyzed,rnwhich have both GONG and MDI observations, to con-rntribute to the intercomparison of the various local helio-rnseismic techniques.