On Variation of the Latitudinal Structure of the Solar Convection Zone

Abstract

The latitudinal sound-speed structure of the Sun's convection zone gives insight into the physical processes occurring there, specifically the cellular convection and possibly the presence of magnetic fields. Using helioseismic data from the GONG network and MDI instrument on SOHO, we map the latitudinal acoustic structure of the convection zone from 1995 to 2002. The temporally averaged structure confirms previous findings of an excess in sound speed at the $10^{-4}$ level at 60 degrees latitude. There also appear to be some variations with time, with the peak in sound-speed asphericity at 60 degrees growing towards the maximum of solar activity according to the MDI data. However, we present some evidence that such variation may be associated with instrumental variation between the epochs before and after SOHO was temporarily lost in 1998. Nonetheless, some genuine temporal variation may be present, and we discuss the possible physical causes of that.

9 pages, to appear in Astron. Astrophys

References in corpus (3)

• The subsurface radial gradient of solar angular velocity from MDI f-mode observations
• Temporal variations of solar rotation rate at high latitudes
• Solar-cycle variation of the sound-speed asphericity from GONG and MDI data 1995-2000

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• On the magnetic field required for driving the observed angular-velocity variations in the solar convection zone