Paper#: 136
Poster #: 27
Session Name: Poster Session 1
Room: East Ballroom
Day: Tuesday
Time: 10:10 a.m.-Noon
Abstract Title: 3D Warm Plasma MHD Theory of Field Line Resonances in the Magnetosphere
PresentSurname: Cheng, C.Z.
All Authors: C.Z. Cheng, S. Zaharia
Abstract : Field line resonance has also been considered as a mechanism for the auroral arc formation because several field line resonance characteristics are found to be correlated well with those of auroral arcs characteristics such as small arc thickness and narrow frequency band (in 1 - 4 mHz range) in luminosity power spectrum. Here, we present a new theory of MHD field line resonance in the magnetosphere by allowing arbitrary isotropic pressure distribution in the equatorial plane. A new contribution due to the longitudinal pressure gradient and geodesic magnetic field curvature is found in the shear Alfven field line resonance equation. This new term together with the coupling between shear Alfven waves and slow magnetosonic waves due to plasma pressure and cause the shear Alfven FLR frequency to be reduced to the 1 - 4 mHz range observed at auroral latitudes. Numerical solutions of the field line resonance frequencies in the auroral region are presented for 3D magnetospheric field in equilibrium with plasma pressure as well as 3D model magnetic fields such as Tsyganenko's models.