EDP Sciences
Free Access
Volume 399, Number 1, February III 2003
Page(s) 329 - 336
Section Diffuse matter in space
DOI https://doi.org/10.1051/0004-6361:20021760
Published online 05 February 2003

A&A 399, 329-336 (2003)
DOI: 10.1051/0004-6361:20021760

On variation of the latitudinal structure of the solar convection zone

H. M. Antia1, S. M. Chitre2 and M. J. Thompson3

1  Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
2  Department of Physics, University of Mumbai, Mumbai 400098, India
3  Space and Atmospheric Physics Group, The Blackett Laboratory, Imperial College, London SW7 2BW, UK

(Received 26 September 2002 / Accepted 22 November 2002)

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 variation 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.

Key words: Sun: oscillations -- Sun: interior -- Sun: rotation -- Sun: activity -- methods: data analysis

Offprint request: H. M. Antia, antia@tifr.res.in

© ESO 2003

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