A selfconsistent marginally stable state for parallel ion cyclotron waves
Abstract
We derive an equation whose solutions describe selfconsistent states of marginal stability for a protonelectron plasma interacting with parallelpropagating ion cyclotron (IC) waves. Ion cyclotron waves propagating through this marginally stable plasma will neither grow nor damp. The dispersion relation of these waves, ω(k), smoothly rises from the usual MHD behavior at small k to reach ω = Ωp as k > +/ ∞. The proton distribution function has constant phasespace density along the characteristic resonant surfaces defined by this dispersion relation. Our equation contains a free function describing the variation of the proton phasespace density across these surfaces. Taking this free function to be a simple ``box function'', we obtain specific solutions of the marginally stable state for a range of proton parallel betas. The phase speeds of these waves are larger than those given by the cold plasma dispersion relation, and the characteristic surfaces are more sharply peaked in the υ⊥ direction. The threshold anisotropy for generation of ion cyclotron waves is also larger than that given by estimates which assume biMaxwellian proton distributions.
 Publication:

Physics of Plasmas
 Pub Date:
 March 2012
 DOI:
 10.1063/1.3697721
 arXiv:
 arXiv:1203.1938
 Bibcode:
 2012PhPl...19c2116I
 Keywords:

 dispersion relations;
 plasma Alfven waves;
 plasma density;
 plasma instability;
 plasma interactions;
 plasma magnetohydrodynamics;
 52.35.Bj;
 52.30.Cv;
 52.40.w;
 52.25.b;
 52.35.Py;
 Magnetohydrodynamic waves;
 Magnetohydrodynamics;
 Plasma interactions;
 Plasma properties;
 Macroinstabilities;
 Physics  Plasma Physics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 in press in Physics of Plasmas