Electron temperature and density of magnetospheric plasma from geotail spacecraft potentials

The spacecraft potential is an index giving the density and temperature of electrons surrounding spacecraft, as understood from the single probe theory. We investigate the correlation between electron density derived from the plasma wave and spacecraft potential observations of the GEOTAIL spacecraft in the solar wind and magnetosphere. We have obtained the good correlation between them within the voltage range of spacecraft potential less than 35V which may mean that electron density is in the range above 0.02 cm ^-3 . We could estimate the electron temperature in the regions of solar wind and electron foreshock, and we found the cases that the electron temperature is higher when the Langmuir wave appears than when no Langmuir wave appears. Then, accumulating many observations of electron density along the GEOTAIL trajectory, we obtained a map showing the global plasma population, in which the bowshock and magnetopause positions are found to be nearly same with the their average positions during the magnetically quiet times.