Density dependent fluctuations of a magnetized non-uniform plasma at the marginal equilibrium

Abstract

A non-uniform magnetized plasma which admits a marginal mode such that in its unstable neighbourhood the real part of the dielectric constant is negative, is subject to sizeable electrostatic saturated fluctuations whose level corresponds to the existence, in this neighbourhood and in statistical sense, of a stable nonlinear Vlasov equilibrium (which is static in the reference frame moving with the phase velocity of the mode). The fluctuation level is calculated using a statistical method and the fluctuations are large as a consequence of the importance of the nonlinear terms near the marginal point. Two examples are discussed considering a plasma with uniform temperature in a uniform magnetic field and in plane geometry: (1) the drift instability originated by the density gradient and (2) the flute instability originated by a gravitational field.