Mode-conversion effects in modeling ionospheric interaction experiments

The propagation of radio waves in an inhomogeneous magnetized plasma with a complex permittivity tensor is investigated to study linear mode-conversion during ionospheric modification experiments. Time-dependent Schrodinger type equations are derived for the propagation of the O and X modes in inhomogeneous magnetized plasmas. The one-dimensional (1D) and two-dimensional (2D) full-wave electromagnetic codes to solve these equations with implemented perfectly matched layer boundaries have been developed. Recent results in ionospheric modification studies at high latitude facilities (Tromso, HAARP) and earlier experiments at the Sura facility, have indicated that the enhancement caused by HF radio waves is localized near the field-aligned position. Analysis of the numerical results for a normal vertically stratified ionosphere and a tilted ionosphere will be presented. We will also present results relevant to the E-region experiments at Tromso. The topside E-region enhancements observed are likely due to linear mode conversion and Z mode propagation to the topside E region. The characteristics of the mode-conversion process have been investigated for linear and parabolic density profiles as the angle of incidence of the heater wave is varied.