Abstract The propagation of hydromagnetic and low frequency radio waves in all directions in a fully ionized gas containing a magnetic field is examined. For longitudinal and transverse propagation the addition of one extra term in the magneto-ionic formulae (without collisions) accounts for the presence of heavy ions. The partition of energy of disturbance between kinetic ( K) and magnetic ( M) for longitudinal propagation of all frequencies is given by K=V 2 k 2 σ 2 M 1− σ 2 k 2c 2 2 where V is the Alfvén speed. Thus approximate equipartition may exist for some audio- and radio-frequencies in the Earth's exosphere. Some errors in Paper I of this series are corrected.