摘要：We characterize, for the first time, type-II spicules in Ca IIK 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3minimum best representing the velocity of the spicules. The K2features are either suppressed by the Doppler-shifted K3or enhanced via increased contribution from the lower layers, leading to strongly enhanced but unshifted K2peaks, with widening towards the line core as consistent with upper-layer opacity removal via Doppler-shift. We identify spicule spectra in concurrent IRIS Mg IIk 2796Å observations with very similar properties. Using our interpretation of spicule chromospheric line formation, we produce synthetic profiles that match observations.
