Abstract
We show that the two-dimensional E x B and Rayleigh-Taylor driven turbulence in the weakly ionized plasma of the Earth's ionosphere to the viscous convection of an ordinary fluid in a porous medium due to temperature gradients (E is the ambient electric field and B is the magnetic field). The turbulence results in fluctuations of the electron density which have been observed for several decades by incoherent radar backscattering techniques and rocket mounted instruments. A two-dimensional single field equation has been derived to describe this convective turbulence. Numerical simulations of this equation reveal a strong anisotrophy in the turbulence, which consists of rising hot bubbles and falling cool bubbles. These bubbles break up into fingers. Sharp gradients are generated in the direction perpendicular to gravity or equivalently the driving electric field E. After reaching a quasisteady state, the omnidirectional energy spectrum approaches k-2. Physical mechanisms leading to anisotrophy are analysed. An equation, analogous to that for the convective ionospheric plasma, but applicable instead to the two-dimensional convection in the Earth's mantle is derived and simulated. The results from this simulation are discussed.
PACS: 52.35.Ra
Published in Physics Reports 283, 95-119 (1997).
In this work a number of open questions in the theory of ion-temperature-gradient-driven turbulence are considered. A simple model is introduced as a paradigm of more complex plasma turbulence models. Special emphasis is placed on those issues that are relevant for the understanding of turbulent transport.
PACS: 52.35.Ra; 52.25.Fi; 47.27.Qb
Keywords: Plasma; Turbulence; Transport; ITG; Tokamak
Published in Physics Reports 283, 121-146 (1997).
The nonlinear plasma transport mechanisms that control the collisionless heating in the Earth's magnetosphere and the onset of geomagnetic substorms are reviewed. In the high-pressure plasma trapped in the reversed magnetic field loops on the nightside of the magnetosphere, the key issue of the role of the ion orbital chaos as the mechanism for the plasma sheet energization is examined. The energization rate is governed by a collisionless conductance and the solar wind driven dawn-to-dusk electric field. The low-frequency response function is derived and the fluctuation dissipation theorem is given for the system. Returning to the global picture the collisionless energization rate from the transport physics is the basis for a low-dimensional energy-momentum-conserving dynamical model of magnetospheric substorms.
PACS: 94.30.-d; 94.30.Lr; 52.30.-q; 52.25.Fi; 94.20.Ww; 94.30.Ej
Published in Physics Reports 283, 165-302 (1997).
(Received 7 August 1996; accepted 20 October 1996)
A new gyrokinetic equation is derived for rotating plasmas with large flow velocities on the order of the ion thermal speed. Neoclassical and anomalous transport of particles, energy, and toroidal momentum are systematically formulated from the ensemble-averaged kinetic equation with the kyrokinetic equation. As a conjugate pair of the thermodynamic force and the transport flux, the shear of the toroidal flow, which is caused by the radial electric field shear, and the toroidal viscosity enter both the neoclassical and anomalous entropy production. The interaction between the fluctuations and the sheared toroidal flow is self-consistently described by the gyrokinetic equation containing the flow shear as the thermodynamic force and by the toroidal momentum balance equation including the anomalous viscosity. Effects of the toroidal flow shear on the toroidal ion temperature gradient driven models are investigated. Linear and quasilinear analyses of the modes show that the toroidal flow shear decreases the growth rates and reduces the anomalous toroidal viscosity. © 1997 American Institute of Physics. [S1070-664X (97)01302-5]