Wave behaviour near critical frequencies in cold bi-ion plasmas

There are numerous circumstances within the solar system where heavy ions and/or even ultramassive charged dust particles co-exist with a proton plasma. This paper analyses some properties of electromagnetic waves in a cold plasma which contains a heavy ion species or charged dust grains. Various new critical frequencies are introduced by the presence of heavy charged material; the bi-ion hybrid, cut-off and cross-over frequencies. Our analysis reveals distinctive behaviour in the electrical current at each of the critical frequencies. Specifically, each of the critical frequencies corresponds to an absence of current flow in a particular direction. We speculate on the possible significance of the effects identified in solar system plasma phenomena.