PRELIMINARY COMPARISON OF SOLAR WIND PLASMA OBSERVATIONS IN GEOMAGNETOSPHERIC WAKE AT 1000-EARTH-RADII AND 500-EARTH-RADII

Preliminary comparison of observations in the expected region of the geomagnetic tail with the Ames Research Center solar wind plasma probe at 1000 Earth radii (Pioneer 7, September 1966) and 500 Earth radii (Pioneer 8, January 1968) indicates that the measured plasma characteristics in these regions are similar. In each case intervals of quiescent plasma ion energy spectra are interrupted by abrupt changes in the magnitude and shape of the ion spectra or by complete absence of measurable plasma. Each of these regions is highly disturbed and is most appropriately described by the term 'geomagnetospheric wake'. A comparison with measurements in the near-Earth region of the geomagnetic tail indicates that the characteristics of the geomagnetic tail apparently undergo significant changes between 80Rz and 500Rz. © 1969.