Electromagnetic Field in the Upper Ionosphere Fromhorizontal ELF Ground-Based Transmitter of Finite Length.

We consider the feasibility of detection of electromagnetic response in the upper ionosphere to ground-based large-scale extremely low-frequency (ELF) transmitters by low-orbiting satellites. As an example of such mega transmitters, we consider the ZEVS 82-Hz transmitter and the FENICS facility with decommissioned electric power lines driven by an 0.5–100 Hz oscillator. We numerically simulated the ELF wave energy leakage into the upper ionosphere, generated by an oscillating grounded linear current of finite length suspended above a high-resistance ground. An altitudinal profile of the plasma parameters has been reconstructed using the ionospheric IRI model. The main step in the analysis of the problem is the solution of Maxwell equations in the atmosphere–ionosphere system with the source in the form of a horizontal current dipole. The electromagnetic field is split into potential and vortex components using the potentials introduced. This problem is devoid of axial symmetry, but the potential and vortex components have this symmetry individually. This approach has enabled us to separate the variables and pass to a one-dimensional boundary-value problem using the Hankel transform. A perturbation excited by a horizontal current of finite length is calculated by summing the fields of horizontal current dipoles that are densely distributed along the current line. According to the model proposed, the horizontal ELF antennas with a length of 60 to 100 km driven by a 100–200 A current can provide electric response amplitudes of up to 60–70 μV/m in the upper nightside ionosphere. [ABSTRACT FROM AUTHOR]