Sources of Heavy Ions in the Venusian Magnetosheath and Their Role in Solar Wind Loading Processes

The processes of photoionization and ionization by collisions with electrons of the extended neutral planetary atmosphere, as well as processes of charge exchange with solar wind protons therein, are a source of the heavy ions that were observed in the solar wind near the magnetosheath of Venus. Upward directed diffusion of heavy ions from the ionosphere that is generated by the turbulence on its boundary can also be such a source, though of a different kind. In general, the nonequilibrium plasma distribution, which is formed due to these processes in the interaction region of Venus with the solar wind, is the cause of free energy resulting in the development of plasma instabilities and electromagnetic fluctuations, which, together with ambient electric and magnetic fields, accelerate heavy ions and provide for their pickup into the solar wind stream. In the present paper, the microphysics of processes of loading the solar wind with the heavy ions of planetary origin is discussed in general, and, based on the data of direct measurement of high frequency (HF) fluctuations of electric field onboard the American spacecraft Pioneer Venus Orbiter, estimates of the role of turbulence in the processes of loading near Venus are made. The analysis of a contribution of turbulent diffusion of the cold ionosphere plasma through the ionopause to the population of heavy ions in the magnetosheath is also made. With the same data of Pioneer Venus Orbiter, the contribution of this process to loading and generation of HF oscillations is estimated.