The Poynting vector applied to the complex refractive index in a hot plasma near the electron cyclotron frequency and to the cyclotron resonance observed on topside ionograms

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Abstract

[1] The electron cyclotron resonance is the only fundamental resonance observed on topside ionograms that, up to the present, has not been understood. There is a solution to the hot plasma dispersion equations for the wave frequency f near the cyclotron frequency fH when the wave number k makes a small angle to the Earth's magnetic induction B. For this case, the magnitude of the imaginary part of k is more than half the real part. This means that the group velocity, /dk, where ω = 2πf, is complex. The real part of /dk is too large to explain the cyclotron resonance observations. In addition to the wave number, the dispersion relations for a hot magnetoplasma can be used to obtain the electric and magnetic fields of the cyclotron wave and hence the Poynting vector. Dividing the Poynting energy flux by the energy density of the wavefield, where the energy density is the sum of the electric, magnetic, and electron energy densities, gives the Poynting velocity VP, which is a good approximation to the actual wave energy velocity for f near fH. Cyclotron waves are strongly damped but can exist several milliseconds as observed. The waves radiate from the plane containing B and the dipole antenna L. The waves with f > fH beat with those with f < fH to produce the beat frequency observed on fixed-frequency ionograms.

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