A thin sporadic-E layer in the ionosphere has electron density

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · Waves in plasmas · Waves in plasmas

Plasma Physics, Ch Plasma oscillations and light in an unmagnetised plasma

Problem

n_e = 2.0\times10^{11}\,\mathrm{m^{-3}}

. Treat the electrons as a cold, collisionless fluid. ((a)) Calculate the frequency

f_{pe}

of the electron plasma oscillation supported by this layer. ((b)) State the group velocity of this oscillation for every wavenumber

k

, and explain in one sentence why a localised disturbance of this kind does not travel away from where it was created.