Excitation of zero-frequency magnetic field-aligned currents by ionospheric heating

A V Streltsov,T R Pedersen

doi:10.5194/angeo-29-1147-2011

A V Streltsov, T R Pedersen

Open Access

https://doi.org/10.5194/angeo-29-1147-2011

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Abstract

Abstract. Time-dependent, three-dimensional numerical simulations of the reduced MHD model describing shear Alfvén waves in the magnetosphere provide an interesting prediction superficially similar to results of several ionospheric heating experiments conducted at high altitudes. In these experiments, heating of the ionospheric F-region with a constant/zero-frequency beam of HF waves causes luminous structures in the ionosphere in the form of a ring or a solid spot with a characteristic size comparable to the size of the heated spot. Simulations suggest that spots/rings or similar optical appearance might be associated with a magnetic field-aligned current system produced by the ionospheric heating. Two of the most interesting features of this current system are (1) strong localization across the ambient magnetic field and (2) distinctive non-symmetrical luminous signatures (ring/spot) in magnetically conjugate locations in the ionosphere.

Highlights

Heating of the ionosphere with powerful HF transmitters can cause many different physical phenomena occurring at the same time at the same location
We only want to emphasize that all of these mechanisms relate the parallel electric field to the field aligned currents (FACs) in the wave, and we limit our study to the investigation of how the ionospheric heating with zero-frequency modulation of an HF beam can generate large-amplitude Alfven waves/FACs in the magnetosphere
ULF waves in the magnetosphere can be generated by ionospheric heating via several different physical mechanisms

Summary

Introduction

Heating of the ionosphere with powerful HF transmitters can cause many different physical phenomena occurring at the same time at the same location. We only want to emphasize that all of these mechanisms relate the parallel electric field (and the parallel electron acceleration) to the FAC in the wave, and we limit our study to the investigation of how the ionospheric heating with zero-frequency modulation of an HF beam can generate large-amplitude Alfven waves/FACs in the magnetosphere.

Results

Conclusion