Comparative analysis of Venus and Mars magnetotails

Abstract We have an unique opportunity to compare the magnetospheres of two non-magnetic planetsas Mars and Venus with identical instrument sets Aspera-3 and Aspera-4 on board of the Mars Express and Venus Express missions. We have performed both statistical and case studies of properties of the magnetosheathion flows and the flows of planetary ions behind both planets. We have shown that the general morphology of both magnetotails is generally identical. In both cases the energy of the light ( H + ) and the heavy ( O + , etc.) ions decreases from the tail periphery (several keV) down to few eV in the tail center. At the same time the wake center of both planetsis occupied by plasma sheetcoincident with the current sheetof the tail. Both plasma sheetsare filled by accelerated (500–1000 eV) heavy planetary ions. We report also the discovery of a new feature never observed before in the tails of non-magnetic planets: the plasma sheetis enveloped by consecutive layers of He + and H + with decreasing energies.