On the structure of collisionless magneto—plasma shock waves at super—critical Alfvén—Mach numbers

Ions reflected from the sharp potential rise in a magneto-plasma, perpendicular shock wave result hi a broad, small-amplitude ‘foot’ in the magnetic field proffle. A theory is given for the structure of this foot, which shows its shape to be a rather flat parabolic curve commencing at about half a Larmor radius in front of the shock front proper. The theory also predicts the amplitude of the foot just in front of the sharp rise as a function of Alfvén—Mach number. Close agreement with experiment is found.