Observations of Correlated White‐Light and Extreme‐Ultraviolet Jets from Polar Coronal Holes

Abstract

Time-lapse sequences of white-light images recorded with the Large Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) frequently show long, narrow structures moving outward over the Sun's polar regions at high apparent speeds. By comparing the LASCO observations with Fe XII lambda 195 spectroheliograms made with the Extreme-ultraviolet Imaging Telescope (EIT) on SOHO between 1997 April and 1998 February, we have identified 27 correlated white-light and extreme-ultraviolet (EUV) jet events. In each case, the EUV jet was observed near the limb of the polar coronal hole 20-60 minutes before the corresponding white-light jet was registered in the coronagraph's 2-6 R. held of view. The jets originate near flaring EUV bright points and are presumably triggered by field line reconnection between magnetic bipoles and neighboring unipolar flux. The leading edges of the white-light jets propagate outward at speeds of 400-1100 km s(-1), whereas the bulk of their material travels at much lower velocities averaging around 250 km s(-1) at heliocentric distances of 2.9-3.7 R.. These lower velocities may reflect the actual outflow speeds of the background polar wind.