Excitation of electromagnetic lower hybrid instability in the region of bouncing electron beams

The region of bouncing electron beams in the earth's magnetosphere can be unstable against a non-resonant electromagnetic lower hybrid instability. The instability is purely growing in the rest frame of the plasma, and can be excited either by the temperature anisotropy or the drift velocity of the bouncing electron beams. The growth rates of the instability decrease with the increase of cold electron density. Consequently the growth rate is maximum at the equator where the cold electron density is minimum. The intense turbulence generated by this instability could broaden the bouncing electron beams thereby explaining the observed wider cone width of the beams at the equator. The instability could generate magnetic pulsations in the frequency range of the order Pc1 - Pc3 with typical wavelength (3-10) km in the magnetosphere during magnetic storms or substorms. (author)