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Astron. Astrophys. 326, 1235-1240

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Research Note

Solar rotation inversions and the relationship between a-coefficients and mode splittings

F.P. Pijpers

Theoretical Astrophysics Center, Institute for Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark

Received 3 March 1997 / Accepted 26 May 1997


From the observing campaigns of a number of helioseismic telescope networks such as the Global Oscillation Network Group (GONG) and also from the Solar Heliospheric Observatory satellite (SoHO), helioseismologists now have data on in excess of 20000 oscillation frequencies FORMULA of the modes known collectively as the 5 minute oscillations. Depending on the order and degree of the modes these data are available either as individual frequencies of modes with known radial order n, spherical harmonic degree l, and order m, or as so-called `a-coefficients' which are obtained by fitting polynomials to ridges of power in the FORMULA diagram. Although there is a one-to-one relationship between these two types of data, the conversion between them is not straightforward which complicates comparison of helioseismic inference between the two types of data. Their relationship with each other and with the solar rotation rate is clarified in this paper.

Key words: Sun: rotation - helioseismology

Send offprint requests to: F.P. Pijpers

© European Southern Observatory (ESO) 1997

Online publication: October 1, 1997
Last change: April 8, 1998