HR: 17:00h
AN: SA14A-05    [Abstracts]
TI: Discrete Auroral Radio Emissions
AU: Weatherwax, A T
EM: aweatherwax@siena.edu
AF: Siena College, Physics Department, Loudonville, 12211
AU: * Yoon, P H
EM: yoonp@ipst.umd.edu
AF: University of Maryland, Institute for Physical Science and Technology, College Park, 20742
AU: LaBelle, J
EM: jlabelle@aristotle.dartmouth.edu
AF: Dartmouth College, Department of Physics and Astronomy, Hanover, 03755
AU: Menietti, J D
EM: jdm@space.physics.uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, 52242
AB: The eigenvalue analysis for discrete upper-hybrid/Langmuir waves trapped in cylindrical density structures is carried out. It is shown that in the overdense case (f_pe>f_ce), discrete Langmuir waves are associated with density cavities, while discrete upper-hybrid waves are excited within enhanced density column. Three examples are considered; the Kilometric Continuum (KC) Emission, rocket observation of Langmuir waves in the auroral ionosphere, and the Auroral Roar (AR) Emission. For physical parameters appropriate for KC source region, it is found that the frequency spacing between individual fine structure spectrum is within the observed range of 0.1~1 kHz. McAdams and LaBelle [1999] interpreted recent wideband observations of Langmuir waves in the auroral ionosphere as discrete Langmuir waves in density cavity. This paper formalize their theory. It is shown that discrete spectrum of electric field is largely determined by the electrostatic wave equation although a very low level of of electromagnetic waves is also present. In the case of AR, a theory is developed which describes the existence of discrete upper-hybrid waves trapped in density enhancement. It is shown that upper-hybrid waves can escape the source region and propagate to remote regions by coupling O-mode electromagnetic waves. These findings may be highly relevant to observations of many other ionospheric, magnetospheric, and planetary fine frequency structure emissions.
DE: 2407 Auroral ionosphere (2704)
DE: 2439 Ionospheric irregularities
DE: 2471 Plasma waves and instabilities (2772)
DE: 2481 Topside ionosphere
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005