Whistler waves generation and current closure by a pulsed tether in ionospheric plasmas

Abstract

The dynamic response of ionospheric plasmas is modeled for current sources induced by a pulsed tether. A new method was developed which combines analytic and numerical techniques to study the dynamic response of a 2-D magnetoplasma to a time-dependent current source imposed across the magnetic field. The set of cold electron/ion plasma equations and Maxwell's equations are first solved analytically in ( k ,ω) space. Inverse Laplace and 2-D complex Fast Fourier Transform (FFT) techniques are subsequently used to numerically transform the radiation fields and plasma currents from ( k ,ω) space to ( r,t ) space. These results show that ionospheric plasmas respond to current sources induced by a pulsed tether through the excitation of whistler waves and formation of an expanding local current loop, induced by field-aligned plasma currents. The current loop consists of two antiparallel field-aligned current channels concentrated at the ends of the imposed tether current and a cross-field current region connecting these channels. The latter currents are driven by an electron Hall drift.