HR: 0800h
AN: SM51A-0332    [Abstracts]
TI: Model of Ionospheric Ducts Due to HF-heating
AU: * Perrine, R P
EM: perrine@astro.umd.edu
AF: University of Maryland, Department of Astronomy, College Park, MD 20742 United States
AU: Milikh, G M
EM: milikh@astro.umd.edu
AF: University of Maryland, Department of Astronomy, College Park, MD 20742 United States
AU: Papadopoulos, D
EM: kp@astro.umd.edu
AF: University of Maryland, Department of Astronomy, College Park, MD 20742 United States
AU: Huba, J D
EM: huba@ppd.nrl.navy.mil
AF: Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 United States
AU: Joyce, G
EM: joyce@ppd.nrl.navy.mil
AF: Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 United States
AB: Ducts in the Earth's ionosphere and plasmasphere along magnetic field lines, defined by their density gradients from one field line to any neighboring line, have implications to the transmission of ELF radio waves across the globe. Strong HF heating has been shown to create a depletion of electrons at the heating region, and could lead to a pressure perturbation that propagates along the entire magnetic field line. The objective of this paper is to present a numerical model of ionospheric ducts caused by HF heating. Discussed here are results of simulations using the Sami2 1D ionospheric modeling code, which has been modified to include a flexible source of strong HF heating. Some parameters of the source, including intensity, location, and vertical spread of the irradiated region were varied. A non-linear relationship was found between these source parameters with maximum pressure, temperature, and density perturbations, propagation velocity of density perturbations, and characteristic heating and cooling rates of the HF irradiated region. After the ionosphere and plasmasphere pass a transient stage, as the gas nearly settles into equilibrium, pressure and density perturbations were found to achieve a nearly steady state. The density profile shows electron depletion at the heated region, surrounded by density increases in the regions just below and above the heated region. The density perturbations then propagate deep inside the plasmasphere down to the conjugate F2 point. It should be possible to use these perturbations spreading along the field line as an ionospheric duct.
DE: 2403 Active experiments
DE: 2435 Ionospheric disturbances
DE: 2447 Modeling and forecasting
DE: 2487 Wave propagation (6934)
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting