HR: 11:00h
AN: SM21C-03    [PDF]
TI: Optical Signatures and Models of Dispersive Nonlinear Field Line Resonances
AU: * Rankin, R
EM: rankin@phys.ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta,, Edmonton, AB T6G 2J1 Canada
AU: Lu, J
EM: jlu@space.ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta,, Edmonton, AB T6G 2J1 Canada
AU: Marchand, R
EM: marchand@phys.ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta,, Edmonton, AB T6G 2J1 Canada
AU: Watt, C
EM: cwatt@space.ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta,, Edmonton, AB T6G 2J1 Canada
AU: Donovan, E
EM: eric@phys.ualberta.ca
AF: University of Calgary, Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4 Canada
AB: The nightside auroral zone is threaded by geomagnetic field lines that support localized ultra-low frequency (ULF) shear Alfven field line resonances (FLRs). Small-scale dispersive FLRs are excited through resonant mode conversion of global scale compressional waves that propagate isotropically through the magnetosphere. In the more distant magnetotail, warm plasma dispersive effects exclude the excitation of latitudinally narrow FLR wave fields. Closer to Earth, flux tubes are loaded with colder plasma that favors inertial scale dispersive effects and nonlinear wave processes. We identify preferential locations in the magnetosphere where small-scale discrete arcs preferentially form, and analyze their spatiotemporal characteristics. We demonstrate that the smallest scales form on field lines where two competing wave dispersion mechanisms cancel. Over realistic timescales, this situation naturally occurs as a result of shear Alfven wave ponderomotive forces that are associated with up-flowing ions and Earthward motion of the resonance position in the magnetosphere. The amplitudes, perpendicular widths, and latitudinal dependence of dispersive scale ULF waves are analyzed and compared with CANOPUS magnetometer and meridian scanning photometer data. Optical signatures of FLR-related arcs are also presented, and differences between dawn and midnight region arcs are discussed in the context of anomalously low FLR frequencies (1-4 mHz between L~7-11).
DE: 2451 Particle acceleration
DE: 2471 Plasma waves and instabilities
DE: 2730 Magnetosphere--inner
DE: 2753 Numerical modeling
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting