Dynamics of the solar chromosphere - III. Ultraviolet brightness oscillations from TRACE

We analyze oscillations in the solar atmosphere using image sequences from the Transition Region and Coronal Explorer (TRACE) in three ultraviolet pas sbands which sample the upper solar photosphere and low chromosphere. We ex ploit the absence of atmospheric seeing in TRACE data to furnish comprehens ive Fourier diagnostics (amplitude maps, phase-difference spectra, spatio-t emporal decomposition) for quiet-Sun network and internetwork areas with ex cellent sampling statistics. Comparison displays from the ground-based CaII H spectrometry that was numerically reproduced by Carlsson & Stein are add ed to link our results to the acoustic shock dynamics in this simulation. T he TRACE image sequences confirm the dichotomy in oscillatory behaviour bet ween network and internetwork and show upward propagation above the cutoff frequency, the onset of acoustic shock formation in the upper photosphere, phase-difference contrast between pseudo-mode ridges and the inter-ridge ba ckground, enhanced three-minute modulation aureoles around network patches, a persistent low-intensity background pattern largely made up of internal gravity waves, ubiquitous magnetic flashers, and low-lying magnetic canopie s with much low-frequency modulation. The spatio-temporal occurrence patter n of internetwork grains is found to be dominated by acoustic and gravity w ave interference. We find no sign of the high-frequency sound waves that ha ve been proposed to heat the quiet chromosphere, but such measurement is ha mpered by non-simultaneous imaging in different passbands. We also find no signature of particular low-frequency fluxtube waves that have been propose d to heat the network. However, internal gravity waves may play a role in t heir excitation.