A strategy for fitting partially blended ridges in GONG solar p-mode spectra

Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, UK

Send offprint request to: M.J. Thompson

Received: 1 October 1997
Accepted: 18 March 1998

Abstract

Observations of solar oscillations by the Global Oscillation Network Group (GONG) using a network of telescopes deployed around the Earth eliminate temporal aliases from the oscillation power spectra to a very substantial extent, making the measurement of oscillation mode parameters much cleaner than with single-site observations. However, the problem of spatial aliasing, which arises from the fact that we see only one side of the Sun, still causes some problems. We discuss some of the issues affecting the estimation of medium-l solar acoustic mode parameters from the data obtained by the GONG network, and in particular the contamination by spatial leakage. We determine the areas in the plane in which such leakage is a problem, and finally we describe a method for improving the mode frequency estimation in such regions, thus extending the range of modes for which useful frequency estimates can be obtained.