EXACT ALGEBRAIC DISPERSION-RELATIONS FOR WAVE-PROPAGATION IN HOT MAGNETIZED PLASMAS

A new model is presented for the treatment of wave propagation along a n external magnetic field in a hot collisionless plasma. The analysis is based on the so-called polynomial distribution functions along the magnetic field, and takes account of enhanced fractions of high-energy particles, which are characteristic of rarefied and magnetized astrop hysical plasmas, in comparison with the bi-Maxwellian distributions. T hese new distributions permit the derivation of general dispersion rel ations that are exactly valid for waves with Im (omega) > 0, and repre sent good approximations for those with Im (omega) < 0. Furthermore, t he explicit form of the dispersion relations is shown to be valid for distribution functions of different shapes. Because of their algebraic structure, the solution of the dispersion relations can be shown to b e equivalent to the determination of the roots of complex-valued polyn omials. The cold plasma, the Maxwellian plasma and the so-called quasi -Maxwellian plasma appear in this formalism as asymptotic and special cases. The reliability of the model is demonstrated with the calculati on of dispersion curves, growth and damping rates for several standard modes, and by comparing it with previous calculations carried out usi ng explicit Maxwellian distributions. Finally, the tendency of the sol ar wind to generate ion-cyclotron waves is investigated as a first, ne w application.