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P. Brekke (European Space Agency), N. Brynildsen, P. Maltby, T. Fredvik, O. Kjeldseth-Moe (Inst. Theor. Astrophysics, Univ. Oslo)
Sunspot oscillations in the transition region and corona are observed simultaneously with CDS on SOHO and TRACE. Results obtained from investigations of ten sunspots in 2001 and 2002 are presented. We find that the oscillation amplitude above the umbra increases with increasing temperature, reaches a maximum for lines emitted close to 200 000 K, and decreases for higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal loops. The observed power spectra show one dominating peak, near 6 mHz, and not several, equally spaced resonances as predicted by theories based on the idea of a chromospheric resonator. We conclude that the observations are compatible with upwardly propagating acoustic waves.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.