On the response of ionospheric magnetization to solar wind dynamic pressure from Pioneer Venus measurements

The variation of the average low altitude dayside ionospheric magnetisation with solar wind dynamic pressure is studied using the magnetometer measurements from the Pioneer Venus Orbiter. The data analysed, includes the first three dayside periapsis passes by the orbiter Passes with even low magnetisation values have been included in the analysis. The results indicate a statistically linear relationship between the ionospheric magnetisation and the solar wind dynamic pressure even below the critical pressure for magnetisation adopted earlier by Phillips et al. (1984). Also similar features in the low altitude magnetic field structure are seen to persist for the whole range of solar wind pressures. These observations point to a continuous rather than time evolving mechanism of generation of ionospheric magnetic fields on Venus