[en] Ion temperature and ion density, measured on October 25, 1977 during the flight of the geophysical rocket ''Vertical-6'' by means of five retarding potential analyzers looking into different directions of space, are analyzed. The solar EUV fluxes determined in five wave length bands with a photoelectron analyzer are also given. Using the ion composition and electron temperature, measured simultaneously, it is shown that the average variation of ion temperature with altitude is in agreement with the heating of the ion gas by the ambient electrons. The observed anomalous variation of ion temperature between 700 and 900 km and the measured ion concentration could be explained, if the charge exchange reactions H⁺reversibleO⁺ and diffusion are also taken into consideration. (author)