Cite abstracts as Author(s) (2007), Title, Eos Trans. AGU,
88(52), Fall Meet. Suppl., Abstract xxxxx-xx

HR: 0800h
AN: SA11A-0297
TI: Emission of ELF/VLF Waves by a Modulated Electrojet upwards into
the Ionosphere and into the Earth-Ionosphere Waveguide
AU: * Lehtinen, N G
EM: nleht@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305, United States
AU: Inan, U S
EM: inan@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305, United States

AB: The modulation of the auroral electrojet by a ground-based
ionosphere heating facility is calculated by solving a kinetic
equation for electron distribution function. The resulting current is
used to calculate the emission of ELF/VLF waves both into ionosphere
and into the Earth-ionosphere waveguide. For this purpose, we
developed a finite element method of calculation of electromagnetic
field in a horizontally-stratified ionosphere filled with magnetized
plasma, with arbitrary harmonically-varying current distribution and
the direction of geomagnetic field. This method is proven to be stable
against the loss of precision due to "swamping" of useful modes by
evanescent waves. The electromagnetic field is calculated both in the
Earth-Ionosphere waveguide (at arbitrary horizontal distance and
direction) and in the ionosphere (as a whistler mode). The presented
method requires less computational resources than traditional FDFD and
FDTD methods. The calculated values are compared to ground and
satellite observations of electrojet emissions from modulation by
existing ionosphere heating facilities. In particular, we find that
the emission of the whistler waves upward into the ionosphere is
contained in a relatively narrow channel, even in the absence of
ducting, due to a substantial horizontal size of the emitting
region. We discuss the difference in the treatment of the heating of
free electron by using the kinetic approach and the approach assuming
a thermal (Maxwellian) distribution of electrons.

DE: 2403 Active experiments
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting