Oscillatory behaviour of chromospheric fine structures in a network and a semi-active region

Abstract

In this work, we study the periodicities of oscillations in dark fine structures using observations of a network and a semi-active region close to the solar disc centre. We simultaneously obtained spatially high-resolution time series of white light images and narrow-band images in the H alpha line using the 2D Gottingen spectrometer, which were based on two Fabry-Perot interferometers and mounted in the Vacuum Tower Telescope/Observatorio del Teide/Tenerife. During the observations, the H alpha line was scanned at 18 wavelength positions with steps of 125 m angstrom. We computed series of Doppler and intensity images by subtraction and addition of the H alpha +/- 0.3 angstrom and +/- 0.7 angstrom pairs, sampling the upper chromosphere and the upper photosphere, respectively. Then, we obtained power, coherence and phase difference spectra by performing a wavelet analysis to the Doppler fluctuations. Here, we present comparative results of oscillatory properties of dark fine structures seen in a network and a semi-active region.