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Paper: Wave Modes in a Chromospheric Cavity
Volume: 184, Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations
Page: 206
Authors: Carlsson, M.; Stein, R. S.
Abstract: Observations show enhanced power near 5.3 mHz and 7 mHz and phase jumps near 7 mHz. Interpretations have varied from standing waves, resonant wakes, shock merging and source interference. We investigate these processes using a non-LTE radiation hydrodynamics code. It is shown that the enhanced power at certain frequencies is caused by partial reflections from steep temperature gradients in the photosphere and the transition region. Due to a phase-speed that is very dependent on frequency close to the acoustic cut-off frequency, the lowest mode frequencies are rather insensitive to the location of the upper reflecting layer. Temperature jumps across shocks introduce additional reflection and modify the mode structure. A corrugated and moving transition region washes out the higher frequency modes but does not affect the lowest modes much. The modal structure is superimposed on a wave field that is dominated by propagating waves in the lower chromosphere.
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