In regions where plasmas of different origin interact, the axisymmetry may be broken and the plasma becomes nongyrotropic. All symmetry is lost and the distribution function now depends on all phase space coordinates and , where is the gyrophase angle.
The majority of nongyrotropic plasmas are unstable. The instability excites waves and the nongyrotropy may couple modes which are decoupled in gyrotropic plasma. The wave growth causes scattering and diffusion of the plasma particles until the state of equilibrium is finally stabilized.
A two-dimensional hybrid code is used to carry out the simulation.
References
Motschmann, U., K.-H. Glassmeier, Nongyrotropic distribution of pickup ions at comet P/Grigg-Skjellerup: a possible source of wave activity, J. Geophys. Res., 98, 20977-20983, 1993.
Kafemann, H.D.F., U. Motschmann, Studies of nongyrotropic ion distributions in magneto-plasmas by 2-d hybrid code simulations, SIMPO Newsletter (Kyoto Univ.), 5, 14-19, 1995.
Motschmann, U., H. Kafemann, M. Scholer, Nongyrotropy in magnetoplasma: Simulation of wave excitation and phase space diffusion, Ann. Geophysicae 15, 603-613, 1997.
Motschmann, U., K.-H. Glassmeier, Dispersion and wave excitation in nongyrotropic plasmas, J. Plasma Phys. 60, 111-132, 1998.
Motschmann, U., K.-H. Glassmeier, A. L. Brinca, Nongyrotropic particle distributions in space plasmas, Ann. Geophysicae, 17, 613-622, 1999.
Brinca, A. L., Motschmann, U., F. J. Romeiras, On the dispersion of two coexisting nongyrotropic ion species, Ann. Geophysicae, 17, 1134-1144, 1999.