DOPPLER OSCILLATIONS IN SOLAR PROMINENCES SIMULTANEOUSLY OBSERVED WITH 2 TELESCOPES - DISCOVERY OF A 30-S OSCILLATION

Time series of Doppler shifts are observed simultaneously with two tel escopes in order to separate actual solar velocities from influences o f image motion or unperfect guiding. Several maxima of the power conto urs occur only in the data set from one of the two telescopes and may thus originate from non-solar sources. Considering only those power ma xima which are observed with both telescopes we establish the solar or igin of periods near 20 and 12 min, which may be identified with 'hybr id fast modes' from model calculations. For one prominence a significa nt period of 30 s is detected which theory predicts as a wave guided b y the prominence fine-structures. Our prominence oscillations are rest ricted to spatially small areas of a few arcsec diameter.