Propagating waves transverse to the magnetic field in a solar prominence

Abstract

We have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT) (Ca II and Hα lines), Sacramento Peak Dunn Solar Telescope using the Universal Birefringent Filter (DST/UBF, in Hα, Hβ and Sodium-D lines), THEMIS (Télescope Héliographique pour l Etude du Magnétisme et des Instabilités Solaires/MTR (Multi Raies) spectromagnetograph (He D₃), and the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) in EUV over a 4 hour period on 2012 October 10. The small fields of view of the SOT, DST, and MTR are centered on a large prominence footpoint extending towards the surface. This feature appears in the larger field of view of the AIA/304 Å filtergram as a large, quasi-vertical pillar with loops on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features in the pillar. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and DST data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns of horizontal threads in the pillar. The pulses have a velocity of propagation of about 10 km/s, a wavelength about 2000 km in the plane of the sky, and a period about 280 sec. We interpret these waves in terms of fast magnetosonic waves.