On the role of ion number density disturbances in VLF sprite relaxation

Abstract

VLF sprites are identified by VLF signal perturbations due to upward electric discharges which lead to an appearance of vertical plasma columns. An analytical relaxation model for the charged particle number densities has been developed in order to explain the observations of very strong VLF sprites. A rapid increase in the negative number density during the first a few seconds after the onset of relaxation has been determined. Employing the developed model, the electron conductivity, the positive ion conductivity, and the negative ion conductivity have been calculated. The efects of the disturbance in the ion number density result in an increase in the relaxation time for VLF sprites in the middle atmosphere.