JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 103, NO. A2, PAGES 1969-1979, FEBRUARY 1, 1998
Karine Issautier, Nicole Meyer-Vernet, Michel Moncuquet, and Sang Hoang
We present new in situ solar wind plasma measurements
obtained during Ulysses fast
transit from the south solar pole to the north one, which took place
1 year before the 1996 sunspot
minimum. The data were obtained with
the radio receiver of the Unified Radio and Plasma Wave Experiment, using the
method of quasi-thermal noise spectroscopy, which is relatively immune to
spacecraft potential perturbations and whose density measurements are
independent on gain calibrations. We analyze the electron
density and the core electron temperature.
We deduce their radial profiles in the steady state fast solar wind;
southward of 
latitude, between 1.52 and 2.31 AU,
the total electron density varies as
, while the core temperature
varies as
.
This allows to estimate the
interplanetary electrostatic field using a simplified fluid equation.
We also study, poleward of (where the variance of both parameters
are very low), the histograms of the
electron density and core temperature scaled to 1 AU,
assuming the above determined radial variation.
Each histogram shows a single
class of flow with a roughly normal distribution. We find a mean
electron density of 
in the southern
hemisphere which is about 8%
larger than in the northern one.
The core temperature histogram is centered at a mean of
K in the south, and of 
K in the north.
This small asymmetry may be due to
a genuine solar asymmetry between the two
hemispheres and/or to a temporal variation
since solar activity slightly decreased during the
Ulysses exploration.