Short period coronal oscillations - Observation and interpretation

The result of an experiment devoted to the search of short period coronal waves using the green coronal line 5303 Å of Fe XIV are analyzed. After the subtraction of sky aureola fluctuations, 2 time series of measurements performed at a 40arcsec height over a faint facular area and small changing chromospheric features show power spectra with evidence of Doppler velocity oscillations with periods near 300 s, 80 s, and especially 43 s. However, no prominent intensity fluctuations appeared. The observed waves are considered as good candidates for being resonant Alfvén oscillations viewed at a low level through several legs of coronal arches, with a typical distance between feet being equal to the autocorrelation distance of the network and with foot-points inserted in the photosphere. A model of such an arch is subsequently computed and seems to fit quite well the observed periods and velocity amplitudes. In addition the energy flux balance is evaluated and the role of such waves in the heating mechanism of coronal arches is discussed.