Dynamics of solar active regions I. Photospheric and chromospheric oscillations observed with TRACE

I present results of an international joint observing campaign, which was carried out in September 1999 and 2000, to study the oscillatory behaviour of active regions (ARs). In this contribution I will concentrate on oscillations in the higher layers of the solar atmosphere as observed with the UV filters of the Transition Region and Coronal Explorer (TRACE). I present the distribution of oscillatory power of two extended active regions. I find a number of well-known chromospheric dynamic phenomena such as running penumbral waves, enhanced 5 min power in the plage and network regions and additional 3 min power in the internetwork. In addition, I find that the 3 min power in the surroundings of the AR is decreased, an effect that has not been observed before. From the topology of the magnetic field I infer that this can be explained by an interaction of the acoustic wavefield with the expanding magnetic field of the active region.