Mercury and Mars: The role of ionospheric conductivity in the acceleration of magnetospheric particles

Abstract

Although Mercury and Mars appear to have magnetospheres of comparable size, Mercury's magnetosphere accelerates charged particles, whereas Mars' magnetosphere apparently does not. We propose that this difference results from the fact that rapid steady‐state convection, and the associated particle acceleration, cannot occur in a Martian magnetosphere because of its connection to a highly conducting ionosphere. Mercury, which has no conducting ionosphere and probably an insufficiently conducting surface, can exhibit rapid solar‐wind‐induced convection and hence particle acceleration in its magnetospheric tail.