Volume 525, January 2011
|Number of page(s)||5|
|Published online||30 November 2010|
Height distribution of the power of 3-min oscillations over sunspots
Institute of Solar-Terrestrial Physics,
Lermontov st., 126a, PO Box 291,
2 Physics Department, University of Warwick, Coventry CV4 7AL, UK
Accepted: 28 September 2010
Context. The height structure of 3-min oscillations over sunspots is studied in the context of the recently discovered effect of height inversion: over the umbra, the spatial location of the maximum of chromospheric 3-min oscillation power corresponds to the relative decrease in the power of photospheric oscillations.
Aims. We investigate whether the height inversion of the power of 3-min oscillations is a common feature of the spatial structure of the oscillations for the majority of sunspots.
Methods. Spectrogram sequences of Hα 6563 Å and Fe i 6569 Å over sunspots, acquired with very high cadency (about 2 s or better) are obtained. The distribution of the oscillation power of the line-of-sight velocity signal is studied by using methods of wavelet frequency filtration and Fourier analysis.
Results. The effect of the height inversion is found in 9 of 11 analyzed active regions. The interpretation of this effect is possibly connected to both the decrease in the level of photosphere in sunspot umbrae and the magnetic field topology.
Key words: sunspots / Sun: oscillations / Sun: chromosphere / Sun: photosphere
© ESO, 2010
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