Rotating Transition Region Features Observed with the SOHO Coronal Diagnostic Spectrometer

Abstract

Strong evidence has been found from SOHO-CDS (Solar and Heliospheric Observatory - Coronal Diagnostic Spectrometer) observations to support the hypothesis that rotation plays a major role in the dynamics of transition region features. A comprehensive survey of the CDS daily synoptic rasters has been carried out to select dynamic events by searching for spectral line shifts in the O v emission line at 629.73 Å (formed at a temperature of 2.5×105 K). Unique CDS observations of a macrospicule were reported by Pike and Harrison (1997), and several more macrospicule-like solar features have now been identified in the polar regions both on the limb and disk. These show blue- and red-shifted emission on either side of an axis stretching above the limb from a footpoint region on the disk. These observations are interpreted as indicating the presence of a rotating plasma, a sort of solar tornado. In the examples studied, the rotation velocities increase with height. The implications for coronal heating models are discussed.