Physical processes in the plasma mantle of Venus

The Phobos‐2 observations established the presence of a turbulent region on the dayside, called the mantle, just outside the magnetic barrier at Mars. This mantle is the interaction region of cold Martian ions and the shocked solar wind. This work presents the results of a study, which analyzed data from ten Pioneer Venus orbits, in order to see whether similar wave particle interaction processes also exist in the corresponding region around Venus. The first conclusion is that the apparent physical processes in the mantle are indeed similar around Venus and Mars. The planetary thermal O+ ions outside the ionopause interact with the shocked solar wind and excite electrostatic waves close to the lower hybrid frequency. These wave propagate inwards, heating first the electron and deeper down in the ionosphere the thermal ion population. The observed superthermal ions are believed to be the product of this wave particle interaction process. Our second conclusion is that the wave energy transferred to the thermal electrons is of the right magnitude (∼4×109 eV cm−2 s−1) to provide the supplemental heat source necessary to reconcile observed and calculated electron temperatures in the ionosphere.