Properties of the solar chromosphere Hα spicules as observed spectrally

Abstract

Time succession of 25 Hα spicules has been studied. The spectra are obtained at a height of 6 arc sec during 21 min (38 pictures) with the 53 cm Lyot coronagraph. Total intensities W, widths Δλ and radial velocities V _r are determined (about 650 Hα line profiles). For 14 spicules the sign of V _r varies, for the rest the sign variation is absent or it is doubtful. Characterized period of V _r variation is 3–7 min with a mean amplitude of ± 4km s⁻¹. W and Δλ also vary with a similar period and mean amplitudes equal to 50% and 30% respectively. Δλ dependence of W (Figure 1) points to the existence of two spicules groups: group I (70%) characterized by relatively small W and Δλ (mean values are 0.08 Å and 1.3 Å respectively); group II comprising brighter (W ≈ 0.13 Å) spicules with wider profiles (Δλ ≈ 1.6 Å). Group II may consist of the unresolved, superimposed group I spicules. We believe, that Hα spicules involve formations consisting of separate elements having the temperature of 6000 K and non-thermal velocities of ∼ 25 km s⁻¹.