HR: 0830h
AN: SP11B-04    [Abstracts]
TI: GONG Travel Time Measurements of Meridional Flows for a Decade
AU: * Kholikov, S
EM: kholikov@noao.edu
AF: National Solar Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 United States
AU: Leibacher, J
EM: leib@noao.edu
AF: National Solar Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 United States
AB: We present measurements of sub-surface meridional flows derived from the difference in travel time between northward and southward propagating sound waves, and their variations during the period from May 1995 to February 2004. We show that for measurements at depths of 20 Mm or deeper, the original low spatial resolution GONG data can be used to extend our study of temporal variations of meridional flows back to the previous solar minimum. In addition to the usual approach using velocity images, we demonstrate that spherical harmonic (SH) coefficient time series for m = 0 provide an effective means for filtering for waves that are propagating directly northward or southward. Another advantage of using SH coefficient time series more generally is that phase velocity filtering can be done for any l range, without an implicit of plane-wave assumption.
DE: 2162 Solar cycle variations (7536)
DE: 7536 Solar activity cycle (2162)
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly