Prominence Motions Observed at High Cadences in Temperatures from 10 000 to 250 000 K

Abstract

We report here for the first time observations of prominence velocities over a wide range of temperatures and with a high time cadence. Our study of ultraviolet movies of prominences reveals that multi-thermal features with speeds of 5–70 km s⁻¹ perpendicular to the line of sight are common in the prominences which showed traceable motions. These speeds are noticeably higher than the typical speeds of 5–20 km s⁻¹ observed in Hα data from `quiet' prominences and are more typical of `activated' prominences in which speeds of up to 40 km s⁻¹ have been reported. The observations were performed using five separate datasets taken by the Solar and Heliospheric Observatory's Coronal Diagnostic Spectrometer (SOHO/CDS) in its wide slit overlappogram mode in lines from He i, O v, and Mg ix and a separate prominence observation taken with both the Transition Region and Coronal Explorer (TRACE) in its 1216 and 1600 Å bands and in Hα by the Swedish Vacuum Solar Telescope (SVST) at La Palma. The movies were taken with cadences >1 image per minute and were made simultaneously or near-simultaneously in spectral lines formed at two or more temperatures. We traced motion that lasted for 3 to 20 min and went distances up to 10⁵ km. Most, but not all, of these were chiefly horizontal. In many cases we were able to observe the same motions over temperature ranges from 20 000 to 250 000 K or 10 000 to 100 000 K. Observations are compared with model predictions.