Destruction of Cyclotron Resonances in Weakly Collisional, Inhomogeneous Plasmas.
NAVAL RESEARCH LAB WASHINGTON D C
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It is shown, both analytically and numerically, that cyclotron resonances can be destroyed in dense omega sub rho Omega, where omega sub rho is the plasma frequency and Omega is the cyclotron frequency, weakly collisional, inhomogeneous plasmas when nuOmega k-squared r sub L squared somewhat 1, where nu is the collision frequency and sub L is the mean Larmor radius. The theory is based upon a model Fokker-Planck equation. It is found that the particles make a transition from magnetized to unmagnetized behavior. This is an important result since it indicates that the ion- and electron-cyclotron-drift instabilities transform into their unmagnetized counterparts, the lower-hybrid-drift instability and the ion acoustic instability, respectively. The ion-cyclotron-drift instability or drift-cyclotron instability is examined in detail and is found to become the lower-hybrid-drift-instability in the region of maximum growth when sq.rt.m sub em sub i omegaOmega sub i somewhat nu sub iiOmega sub i somewhat m sub em sub i for T sub e approximately equal T sub i plasmas. The first inequality is required to overcome electron viscous damping, while the second allows the ions to become unmagnetized. Applications to the equatorial F region of the ionosphere and the Tandem Mirror Experiment TMX are discussed. Author
- Atmospheric Physics
- Plasma Physics and Magnetohydrodynamics