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Astron. Astrophys. 316, 457-463 (1996)

Low energy charged particles in the high latitude heliosphere

L.J. Lanzerotti1, C.G. Maclennan1, T.P. Armstrong2, E.C. Roelof3, R.E. Gold3, and R.B. Decker3

1 Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974, USA
2 Department of Physics, University of Kansas, Lawrence, KS 66054, USA
3 The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA

Received 28 February 1996 / Accepted 25 April 1996

Abstract. Low energy ion and electron measurements made over the south and north polar regions of the sun by the HI-SCALE instrument on the Ulysses spacecraft during its solar minimum polar passages are summarized. The polar flux levels were considerably reduced in comparison to fluxes in the vicinity of the heliospheric current sheet. Flux variations with a period of img1.gif 26 days were seen to nearly img2.gif S but were not observed over the northern pole. Solar particle events originating from near-equatorial activity were seen at high southern latitudes, but not at high northern latitudes. Comparisons with in-ecliptic measurements made during the same time interval on the IMP8 spacecraft suggest that the polar differences are largely spatial and not temporal. The flux of low energy ( img3.gif -5.0 MeV/nucl) anomalous oxygen was measured to be img4.gif % higher over the northern polar region than in the south. The flux of solar wind iron, measurable because of its convection into the instrument by the high speed polar solar wind, is estimated to be about a factor of two larger over the south pole than over the north.

Key words: interplanetary medium - Sun: particle emission

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