Observation of CME Source Regions by Coronal Emission-Line Dopplergrams
Abstract
Although observations with SOHO/LASCO show the behavior of CMEs beyond 2.5 solar radii, connection between LASCO CMEs and their source regions in the lower corona observed with SOHO/EIT or Yohkoh/SXT is not trivial. One way to fill the gap would be to supplement the Doppler shift information of the moving CME mass. Such an instrument was built and has been operated since 1997 July at the Norikura Solar Observatory (2876 m above sea level) of NAOJ. The instrument we call NOGIS (NOrikura Green-line Imaging System) is made of a 10 cm-aperture coronagraph and a tunable birefringent filter. NOGIS can provide both intensity and Doppler velocity images of 2 MK plasmas using the coronal green-line emission at 5303 Angstrom of Fe XIV. An intensity image is made by subtracting the sky background (taken at far wings) from the line-center image. A Doppler image is constructed by subtracting a blue-wing image from a red-wing image. The line-of-sight velocity up to 25 km/s can be obtained with an accuracy of about 0.6 km/s. NOGIS covers a field of view of 1.03 - 1.33 solar radii in a full frame mode, or a local small area in a partial frame mode with higher cadence of about 1 minute. So far we have analyzed two CME events which showed favorable orientations of the regions against the plane of the sky (1999 May 7 and 2003 June 2). In both events, interaction between two magnetic flux systems (loops in the case of 1999 May 7 and arcades in the case of 2003 June 2) was observed.
- Publication:
-
2nd UN/NASA Workshop on International Heliophysical Year and Basic Space Science
- Pub Date:
- November 2006
- Bibcode:
- 2006ihy..workE..35S