3/09/2005

return to index page

Results of testing conditions in "The electromagnetic ion cyclotron anisotropy instability" by SP Gary and D Schriver, 1987. Hybrid run results using their dispersion solutions for stable and unstable anisotropic bimaxwellian beam/core distributions are shown below. The dispersion solutions predicted max growth at k x B = 0.

UNSTABLE : Tperp_beam/Tpar_beam = 5.0, Tpar_beam/Tpar_core = 10.0 Fig 1

STABLE : Tperp_beam/Tpar_beam = 5.0, Tpar_beam/Tpar_core = 1.0 Fig 2

UNSTABLE : Tperp_beam/Tpar_beam = 10.0, Tpar_beam/Tpar_core = 1.0 Fig 3

Next, hybrid runs with a ring beam instead of bimaxwellian beam for same conditions as in Fig 1. Here are the initial velocities of the ions in the two cases:

Gary and Schriver bimaxwellian beam: Fig 4	Ring beam: Fig 5

Here are the hybrid run results for the ring beam shown in Fig 5:

Phase Space (red = background fixed, black = beam injected) Fig 6
Velocity Space Fig 7	Velocity Space Fig 8
Velocity Space Fig 9
By Fig 10	Bz Fig 11
Phi Fig 12
B field energy Fig 13
Fourier modes Fig 14

The energy growth for the bimaxwellian beam (Fig 1) and ring beam (Fig 13) are similarly shaped, but the ring does peak sooner and at higher growth rate. For the bimaxwellian beam, Gary and Schriver predicted wave modes propagating both parallel and antiparallel to B. In the book "Computer Simulation of Space Plasmas" where I got the hybrid code, Winske and Omidi (1992) run the Gary and Schriver test shown in Fig 1 (except with relative drift between beam and core of 1 vA) and say that phi "does not show a well defined helicity because because there are waves of comparable amplitudes propagating in both directions".

return to index page