Dynamic fibrils in Hα and C IV

Abstract

Aims. To study the interaction of the solar chromosphere with the transition region, in particular active-region jets in the transition region and their relation to chromospheric fibrils. Methods. We carefully align image sequences taken simultaneously in Civ with the Transition Region and Coronal Explorer and in Hα with the Swedish 1-m Solar Telescope. We examine the temporal evolution of “dynamic fibrils”, i.e., individual short-lived active-region chromospheric jet-like features in Hα. Results. All dynamic fibrils appear as absorption features in Hα that progress from the blue to the red wing through the line, and often show recurrent behavior. Some of them, but not all, appear also as bright features in Civ which develop at or just beyond the apex of the Hα darkening. They tend to best resemble the Hα fibril at +700 mA half a minute earlier. Conclusions. Dynamic chromospheric fibrils observed in Hα regularly correspond to transition-region jets observed in the ultraviolet. This correspondence suggests that some plasma associated with dynamic fibrils is heated to transition-region temperatures.