HR: 0800h
AN: SA31A-1107    [Abstracts]
TI: Inversion Algorithm for Auroral Emissions due to an e-Beam From an Electrically Floating Bare Tether
AU: Charro, M
EM: mcharro@teleline.es
AF: Universidad Politecnica de Madrid, Pza. C. Cisneros 3, Madrid, 28040 Spain
AU: * Sanmartin, J R
EM: jrs@faia.upm.es
AF: Universidad Politecnica de Madrid, Pza. C. Cisneros 3, Madrid, 28040 Spain
AB: A (bare) conductive tether electrically floating in LEO orbit would be an effective e-beam source free of problems that marred standard beams producing artificial auroras. Ambient ions impacting the tether with KeV energies over most of its length liberate secondary electrons that result in emissions in the E-layer. Brightness measurements from the spacecraft for line-of-sight integrated emissions might allow determination of the (neutral) density vertical profile in that critical layer; mixed effects from the variation of beam flux and energy along the tether, and neutral density dependence on altitude, lead to a brightness peak in the beam footprint at the E-layer. Tomographic inversion to determine the density profile is made difficult by beam-broadening in elastic collisions, which tends to flatten the peak, and by the highly-nonlinear dependence of line-of-sight brightness on the density profile. A new inversion algorithm is here presented. The low densities prevailing near the tether, in the F-layer, allow neglecting the energy lost by the electrons down to some altitude. An average density in that region can be estimated using brightness of lines-of-sight farther from the magnetic dip angle. Tomographic inversion then proceeds forwards using brightness of subsequent lines of sight to get density values downwards. Brightness values for lines-of-sight closer to the dip angle allow algorithm iteration. Results for round-wire tethers and tape tethers are compared.
DE: 2403 Active experiments
DE: 2407 Auroral ionosphere (2704)
DE: 2455 Particle precipitation
DE: 2494 Instruments and techniques
DE: 2704 Auroral phenomena (2407)
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting