Instabilities

Abstract

Plasma instabilities can be microinstabilities arising from non-equilibrium distributions in velocity space or macroinstabilities due to gradients in real space. The beam-plasma system is the leitmotif for discussing microinstabilities because it can be treated by simple mathematical models, and can be modified to include boundaries. The method of choice is normal mode analysis, which is seeking for complex values of the wave frequency that indicate temporal growth. Langmuir’s beam-excited plasma oscillations and ion-beam driven Buneman instabilities are examples for beam-instabilities. Macroinstabilities are discussed for pinch plasmas, where the gradient of magnetic pressure drives the instability. The Rayleigh–Taylor instability of the lower ionosphere is an example for the formation of flute modes.

“And if you take one from three hundred and sixty-five, what remains?”

“Three hundred and sixty four, of course.”

Humpty-Dumpty looked doubtful. “I’d rather see that worked out on paper.”

Lewis Carroll, Through the Looking-Glass