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Astron. Astrophys. 316, 342-345 (1996)

Symmetry in discontinuity properties at the north and south heliographic poles: Ulysses

Bruce T. Tsurutani1, Christian M. Ho1, Regina Sakurai1, Bruce E. Goldstein1, Andre Balogh2, and John L. Phillips2

1 Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 169-506, Pasadena, CA 91109- 8099, USA
2 Imperial College of Science and Technology, The Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, England
3 Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Received 5 February 1996 / Accepted 9 April 1996

Abstract. A study of directional discontinuities (DDs) that occurred during 4 days of the Ulysses north polar pass was conducted (461 directional discontinuities total) using magnetic field and plasma data. We find that the total number of directional discontinuities selected by the Tsurutani and Smith (1979) method are the same in the north and south polar regions (within statistical errors) if the radial gradient is taken into account. We also find that tangential discontinuities (TDs) occur at edges of mirror mode structures. Approximately half of these structures are locally unstable. TDs are also associated with interplanetary current sheets, some of which are in regions of positive solar wind velocity gradients. To first order, we find no difference in the number of directional discontinuities, number of TDs, or the types of TDs in the north polar region from the south polar region.}

Key words: interplanetary medium - plasmas

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Last change: December 30, 1996
© European Southern Observatory (ESO) 1996