THEORY AND ANALYSIS OF THE SUPER WHISTLER

Whistlers observed on the ground with frequency cutoffs greater than one-half the equatorial electron gyrofrequency along their field-aligned propagation paths have been termed super whistlers. The rarity of the super whistler is a consequence of the relatively small number of ducts which allow their propagation. The upper cutoff frequency of the super whistler is directly related to the physical structure of the duct. In addition to the path location and equatorial electron density that can be deduced from ordinary whistlers, super whistlers also provide information on density gradients along the magnetic field lines near the equator. Analysis of one set of super whistlers shows that immediately after a magnetic disturbance the equatorial plasma near L equals 4. 5 is in an intermediate state between the collisionless and diffusive equilibrium distributions. plasma distribution approaches that of diffusive equilibrium after a period of low geomagnetic activity.