Spatio-temporal fluctuations in He I 10830 A line parameters - Evidence for spicule formation

Abstract

The equivalent width, line depth, line width, and Doppler shift of the He i 10830 Å line were extracted from two time series of spectra. Scatter plots of time-averaged line depth, line width, and Doppler shifts, as well as the root mean square temporal fluctuation of these quantities against the time-averaged equivalent width at a few hundred spatial locations were obtained. The statistical behaviour of these line parameters and their fluctuations was used to infer plausible reasons for the fluctuations. Examination of these results showed that the line parameter fluctuations could be caused by fluctuations in the coronal UV radiation (which could drive the spicules) or by the appearance of density inhomogeneities such as spicules within the line forming domain. In either case, the data can be interpreted as representing the initial phases of spicules.