Meeting abstract

31st ESLAB Symposium, ESTEC, The Netherlands, 22-25 September 1997

Abstract:
Since passing through the north polar regions of the heliosphere in mid 1995, the Ulysses spacecraft has been gradually returning to lower heliolatitudes, following its polar orbit inclined at 80° to the heliographic equator. During this time the distance of the spacecraft from the Sun has also increased back out to around 5 AU. This paper reports on the observations of the heliospheric magnetic field obtained by the magnetometer experiment on Ulysses since the spacecraft once again began to come under the influence of the heliospheric streamer belt in August of 1996. The first signature of an interaction region in the magnetic field data was seen at a heliographic latitude of 30°N and the first crossing of the heliospheric current sheet at a latitude of 25°N. Both of these latitudes are higher than might have been expected for the typical tilt of the heliospheric current sheet at a time of solar minimum activity. By mapping the observed magnetic field features at Ulysses back to estimate their source locations at the Sun, we have looked for features in the photosphere and corona which might help explain the Ulysses observations. This study has shown that the higher than expected latitude at which Ulysses encountered the current sheet was due to a long-lived active region in the corona at about 240° Carrington longitude which produced a pronounced northward warp in the current sheet structure. We further extend this study through the more recent Ulysses magnetic field measurements.