Ulysses observations of a recurrent high speed solar wind stream and the heliomagnetic streamer belt
Abstract
Near-ecliptic solar wind observations by Ulysses on its way to the polar regions of the Sun, compared with those from IMP 8 at 1 AU, showed that high-speed streams decay and broaden with heliocentric distance from IMP 8 to Ulysses, as expected. In July 1992 while travelling south at ∼13°S and 5.3 AU, Ulysses encountered a recurrent high-speed stream, that may also have been observed at IMP 8. The stream has been observed a total of 14 times, once in each solar rotation through June 1993 at ∼34°S. The source of the high-speed stream is an equatorward extension of the south polar coronal hole. From July 1992 through June 1993, averages of solar wind peak speed increased while density decreased with heliographic latitude. Both the stream and a low-speed, high-density flow, presumably associated with the heliomagnetic (coronal) streamer belt encircling the heliomagnetic equator, crossed Ulysses with the solar rotation period until April 1993 when the spacecraft was at ∼29°S heliographic latitude. After this time, as the spacecraft climbed to higher latitudes, the central portion of the streamer belt with lowest speed and highest density disappeared. Therefore, at its maximum inclination, the belt was tilted at ∼29° to the heliographic equator at this point in the solar cycle.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- November 1993
- DOI:
- 10.1029/93GL02630
- Bibcode:
- 1993GeoRL..20.2323B
- Keywords:
-
- Current Sheets;
- Magnetohydrodynamic Flow;
- Solar Magnetic Field;
- Solar Wind Velocity;
- Stellar Mass Ejection;
- Coronal Holes;
- Mapping;
- Spectroheliographs;
- Three Dimensional Models;
- Ulysses Mission;
- Interplanetary Physics: Solar wind plasma;
- Interplanetary Physics: Sources of the solar wind;
- Solar Physics;
- Astrophysics;
- and Astronomy: Corona and transition region