Meeting abstract

AGU Fall Meeting, San Francisco, 6-10 December 1998

Abstract: As part of its routine operations, the Coronal Diagnostic Spectrometer (CDS) on SOHO makes a daily set of images along the central meridian of the Sun in a number of spectral lines. These images are used to produce synoptic Carrington maps which show the locations of active regions, coronal holes, bright points and the basic structure of the chromosphere and lower corona. By mapping back the position of interplanetary spacecraft, using measured solar wind speeds (assuming constant speed over the distance from the Sun), it is possible to estimate the time and Carrington longitude of origin of the solar wind reaching the spacecraft and hence the source of the magnetic field lines passing through the spacecraft. Using this technique we have investigated the relationship between the patterns of coronal holes and active regions at the Sun and the large scale structure and dynamics of the solar wind and heliospheric magnetic field observed principally by the Ulysses spacecraft during mid 1996 to mid 1998, and also for some specific intervals during this time by the WIND spacecraft. This period began close to solar minimum and has continued through the time that solar activity has begun to increase towards the next maximum. Early in the period, interplanetary conditions were dominated by high speed streams of solar wind originating from the coronal holes, producing Corotating Interaction Regions, while more recently transient events originating from near the active regions are becoming more common. As a sideline of this study, it has also been possible to identify the solar events producing some of the energetic particle showers which degrade the CDS images.