HR: 11:20h
AN: SM22A-05 [Abstracts]
TI: Analysis of electron distributions associated with the source of auroral roar
AU: * Bounds, S R
EM: scott-bounds@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy
210 Van Allen Hall, Iowa City, IA 52242
United States
AU: Kletzing, C A
EM: craig-kletzing@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy
210 Van Allen Hall, Iowa City, IA 52242
United States
AU: LaBelle, J
EM: jlabelle@einstein.dartmouth.edu
AF: Dartmouth College, Department of Physics and Astronomy, Hanover, NH 03755
United States
AU: Samara, M
EM: marilia@aristotle.dartmouth.edu
AF: Dartmouth College, Department of Physics and Astronomy, Hanover, NH 03755
United States
AB:
In January of 2003, the HIgh Bandwidth Auroral Rocket (HIBAR) passed through two separate regions of strong upper hybrid
emission in which the upper hybrid frequency was twice the electron cyclotron frequency $(f_{uh} = 2 f_{ce})$ [\textit{Samara
et~al},2004]. These emissions are believed to be the source of HF auroral roar wave emission often observed on ground based
receivers. The current theoretical model implies that the electro-magnetic waves observed on the ground are produced through
mode conversion of strong emission of upper hybrid waves near 2 and 3 times the cyclotron frequency. The cyclotron maser
theory predicts that the Z mode wave undergoes significant growth when the local upper hybrid frequency is just below
$(\sim1%)$ twice the electron cyclotron frequency and with the appropriately unstable distribution of energetic electrons
[\textit{Yoon et~al.}, 1996,1998,2000]. Though roar is frequently observed from the ground, the source region has rarely
been identified in-situ. Analysis of the in-situ electron distributions from HIBAR show qualitative agreement with the
theoretical distributions used by \textit{Yoon et~al.},1998. HIBAR encountered three distinctly separate regions where
$f_{uh} \sim 2 f_{ce}$, two of these regions include strong upper hybrid emission, while the third is void of upper hybrid
wave activity. The measured particle distributions demonstrate that, in the two regions with wave emission, the electron
cyclotron maser instability condition is achieved and that, in the third region without wave emission, the instability
condition fails.
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\end{thebibliography}
DE: 7867 Wave/particle interactions
DE: 7871 Waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting