SOHO CoRoT Kepler Picard SDO GONG

The Influence of Tracking Rate on Helioseismic Flow Inferences


Haber Deborah


JILA, University of Colorado


Local helioseismology
Auteur(s) supplémentaire(s)Swati Routh, Bradley W. Hindman, Richard S. Bogar, Juri Toomre
Institution(s) supplémentaire(s)Stanford University


Solar rotation supplies a huge background signal to the helioseismic study of convective motions
and interactions of strong magnetic fields with subsurface flows. The presence of differential
rotation also complicates one's choice of reference frames and how individual regions are
identified. The Helioseismic and Magnetic Imager pipeline will track the tiles used in ring
analysis at the solid-body Carrington rate in order to simplify the labeling and identification
of tracked regions. Such a system permits the easy retrieval and construction of tracked
velocity cubes of varying temporal durations which keep the same latitudinal and longitudinal
designations. Tracked data cubes from the Michelson Doppler Imager, on the other hand,
were most often tracked at the differential Snodgrass rate appropriate to the central
latitude of the tracked tile. This choice was made in order to remove as much of the
rotational flow signature as possible.

Here we intercompare the flow determinations that result from the two tracking schemes.
Thousands of tiles, each spanning 5 degrees in heliographic angle, are tracked separately at
each rate and processed with standard ring-analysis procedures to obtain mean flow speed
estimates for a broad range of p modes. The two sets of flows are compared to ascertain if
systematic differences are observed. We examine the mean difference between the two sets as a
function of position on the solar disk as well as mode frequency and wavenu
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