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Simulations of ELF radiation generated by heating the high-latitude D region

H. L. Rowland

Plasma Physics Division, Naval Research Laboratory, Washington, District of Columbia


Three-dimensional simulations show the ELF (extremely low frequency) radiation generated by heating the high-latitude D region and modulating the polar electrojet. The simulations use a time-varying current perturbation in the D region. The ELF radiation is calculated in the Earth-ionospheric waveguide to a radial distance of 2400 km. The angular and radial dependence and the polarization of the horizontal, ground-level magnetic field are determined. The radiation pattern is a combination of a linear dipole antenna and a right-hand circular antenna. At ELF frequencies because of low D region absorption the dipole is dominant. The polarization and field strength in the near-field can predict the orientation of the radiation pattern and the wave amplitude in the far-field. The near-field polarization indicates the direction and strength of the electrojet. As the electromagnetic wave propagates in the waveguide, it drives whistlers waves into the D region. Because of reflection from the D region the mode inside the waveguide is not purely transverse. This gives a counterclockwise rotation to the polarization. Directly above the heated region, waves are also launched along the Earth’s magnetic field. The near-field polarization shows good agreement with observations from the high-power auroral stimulation array (HIPAS) and Tromsø. © 1999 American Geophysical Union

Index Terms: 2403 Ionosphere: Active experiments; 2407 Ionosphere: Auroral ionosphere (2704); 2411 Ionosphere: Electric fields (2712); 0689 Electromagnetics: Wave propagation (4275).

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Citation: Rowland, H. L. (1999), Simulations of ELF radiation generated by heating the high-latitude D region, J. Geophys. Res., 104(A3), 4319–4328.