Time-resolved spectral observations of spicule velocities at several heights

Abstract

The vacuum telescope of the National Solar Observatory, Sacramento Peak was used to obtain H-alpha spectral observations of spicules. A set of spectra corresponding to five slit positions above the solar limb were recorded every 8 s in order to study the temporal variation of spicules at several heights with high space and time resolution. The short time interval (less than 2 s) between exposures at each height is a new feature of these observations. A typical flow event in a spicule was found to last 10-15 minutes. During this period the velocity did not reverse sign. The temporal behavior of the velocity at different heights in a spicule appeared to show a high correlation, with a time lag less than 7 s, implying signal propagation speeds greater than 300 km/s. Finally, no significant variation of spicule velocity with height in the chromosphere was noticed.