Dynamics of solar magnetic arches in the photosphere and the chromosphere

Mass motions in chromospheric arch filaments have been observed with imaging spectroscopy (MSDP) at the VTT telescope of the Teide Observatory. Coordinated observations of time sequences of continuum images were carried out at the SVST telescope of the Observatorio del Rogue de los Muchachos, which provided transverse velocities of photospheric tracers, by ''local correlation tracking.'' Her profiles along 3 arch filaments are analysed in terms of ''differential cloud model'', to discuss the Doppler velocities of chromospheric material. Models of ascending arches with downflows in both legs are investigated. The gas pressure is neglected, but the free-fall equations are integrated versus time (non-stationary case). We first assume circular lines of force with constant radius. We can account for chromospheric velocities, but we cannot fit the slow motion of footpoints derived from photospheric tracers. A better agreement is obtained by assuming lines of force with fixed footpoints and variable radius. Typical values are: half distance between footpoints of 10 to 15 Mm, upward velocity at the top of loops of 4 km s(-1) after an integration time of 800 s. The obtained values are consistent with the sizes and the lifetime of arch filaments.