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

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 fieldaligned 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.

Artificial Aurora Produced by HAARP

“…Figure shows a snapshot of the field‐aligned current density inside the 3‐D domain at the time t = 158.5 s after the heating has begun. In full agreement with Streltsov and Pedersen (), the simulations demonstrate that such constant heating leads to a rapid formation of two FACs that are closed through the ionosphere in both hemispheres. The structure of the currents obtained in our simulations is different from the structure of currents shown by Streltsov and Pedersen ().…”

“…In full agreement with Streltsov and Pedersen (), the simulations demonstrate that such constant heating leads to a rapid formation of two FACs that are closed through the ionosphere in both hemispheres. The structure of the currents obtained in our simulations is different from the structure of currents shown by Streltsov and Pedersen (). Namely, in our simulations, the heating produces two current channels standing side by side, and in the simulations by Streltsov and Pedersen (), the currents form an axisymmetric structure.…”

“…These observations are shown in Figure b, which gave a strong reason to conclude that during the experiment HAARP indeed produces magnetic FACs flowing into the magnetosphere. This conclusion is also supported by Streltsov and Pedersen (), who showed with 3‐D MHD simulations that some luminous structures (in particular, rings and solid spots) produced by HAARP in the O‐heating experiments can be interpreted in terms of ULF waves and FACs.…”

“…In this paper, we make the next step in the development of the numerical model used by Streltsov and Pedersen () by including the Hall conductivity in the ionosphere and using a more realistic heating mechanism. Namely, the model assumes that the heating decreases the recombination coefficient in the ionospheric E region, and the decrease in the recombination increases the density.…”

“…The 3‐D two‐fluid reduced MHD model has been described in detail in several papers devoted to the electrodynamic coupling between the ionosphere and the magnetosphere at high latitudes (Jia & Streltsov, ; Streltsov & Pedersen, ), and it is mentioned here only for completeness. The magnetospheric part of the model consists from electron parallel momentum equation the current continuity equation and the density continuity equation where subscripts ‖ and ⊥ indicate parallel and perpendicular vector components to b = B 0 /B 0 , respectively, v e is the electron velocity, n 0 is the background quasi‐neutral plasma density, T e is the background electron temperature, f e is the electron collision frequency, is the Alfvén speed, and m i is the proton mass.…”