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Astron. Astrophys. 316, 430-434 (1996)

Latitude dependence of Solar Wind plasma thermal noise: Ulysses radio observations

S. Hoang, N. Meyer-Vernet, K. Issautier, M. Maksimovic, and M. Moncuquet

Observatoire de Paris-Meudon, DESPA, URA 264 CNRS, F-92195 Meudon, France

Received 19 February 1996 / Accepted 9 April 1996

Abstract. Thermal noise spectroscopy was performed on the URAP radio receiver data for the first time out of the ecliptic during the Ulysses spacecraft transit from southern to northern heliolatitudes. We present the results on the solar wind electron density and bulk temperature obtained from img1.gif to img2.gif . They indicate a rough symmetry of the solar wind electron plasma about the solar equator. The latitudinal gradient of the electron bulk temperature was found to be approximately img3.gif latitude southward and img4.gif northward. Within img5.gif latitude, large fluctuations in the 1-AU scaled electron density and temperature were observed and presumably linked to the corotating structures existing in the equatorial band. Effects of the solar wind speed on the thermal noise spectra were highest at high latitudes as predicted. They will be fully taken into account in future work.

Key words: solar wind - interplanetary medium - plasmas - Sun: radio radiation

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