The effect of temperature on the rate of growth of the leading edge of a collisionless shock

An equation is derived for the characteristic length scale of the leading edge of a laminar shock propagating perpendicular to a magnetic field into a hot plasma. Where the upstream plasma has a low value of beta , it is shown that the main correction to the cold plasma result comes from the thermal motion of the ions rather than the electrons. This may be of interest in connection with current theories on collisionless shocks which start from a laminar leading edge, then consider the instabilities which can occur and which will give rise to a high level of turbulence in the middle of the shock.