AAS 200th meeting, Albuquerque, NM, June 2002
Session 4. Helioseismology and the Solar Interior
Display, Monday, June 3, 2002, 9:20am-6:30pm, SW Exhibit Hall

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[4.09] Calculating the GONG and GONG+ leakage matrices -- latest improvements

R. Howe, F. Hill (NSO)

In helioseismology, time series for each spherical harmonic are calculated by convolving the imaged data with spherical harmonic masks. Because we image only a part of the solar surface, each time series is contaminated by power from neighbouring spherical harmonics. This contamination can be quantified by calculating the so-called `leakage matrix'. Many data analysis techniques depend on a good estimate of this matrix. Motivated by the new GONG+ data, we have improved the calculation of the leakage matrices for both GONG+ and GONG Classic images. Specifically, we have improved the grids used for calculating the apodization; incorporated an empirical projection function; and allowed for the different pixel aspect ratios and image apodization functions of GONG+ and GONG Classic data. The effect of these improvements will be shown through several comparisons between the calculated matrices and the observed power spectra.

NSO is operated by AURA, Inc. under a co-operative agreement with NSF.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.