A&A 407, 735-740 (2003)
Dynamics of the solar chromosphere IV. Evidence for atmospheric gravity waves from TRACER. J. Rutten and J. M. Krijger
Sterrekundig Instituut, Postbus 80 000, 3508 TA Utrecht, The Netherlands
(Received 23 July 2002 / Accepted 6 June 2003 )
We study the low-frequency brightness modulation of internetwork regions in the low solar chromosphere using simultaneous ultraviolet and white-light image sequences from the Transition Region and Coronal Explorer (TRACE). The ultraviolet sequences exhibit a slowly varying brightness pattern in internetwork regions on which the more familiar acoustic three-minute oscillation is superimposed, with about half of the peak brightness reached in internetwork grains contributed by the low-frequency background. We address the nature of the latter, applying two-dimensional Fourier filtering to isolate it from the acoustic modulation. Spatio-temporal comparisons and selective time-delay scatter correlations between the ultraviolet and white-light low-frequency sequences establish that reversed granulation constitutes at most a minor part of the ultraviolet background. Fourier analysis shows that the meso-scale contribution dominates and consists of atmospheric gravity waves.
Key words: Sun: photosphere -- Sun: chromosphere -- Sun: oscillations
Offprint request: R. J. Rutten, R.J.Rutten@astro.uu.nl
© ESO 2003