HR: 0800h
AN: SM51A-1278 [Abstracts]
TI: Nonlinear Dynamics of Compressional Magnetic Turbulence in the Earth's Magnetosphere
AU: * Crabtree, C
EM: cecrabtre@uci.edu
AF: University of California - Irvine, 4129 Frederick Reines Hall, Irvine, CA 92614
United States
AU: * Crabtree, C
EM: cecrabtre@uci.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
United States
AU: Chen, L
EM: liuchen@uci.edu
AF: University of California - Irvine, 4129 Frederick Reines Hall, Irvine, CA 92614
United States
AB:
Ultralow frequency compressional magnetic turbulence has been observed
in the Earth's magnetosphere for decades. Many linear theories have
been proposed to describe these observations, such as Drift-Mirror
modes, compressional trapped particle modes, and drift compressional
modes; however, there are no ``self-consistent'' nonlinear theories.
The observed fluctuation levels δ B|/B are on the order of
10% and the nonlinear frequency derived from the turbulence induced
drift velocity is on the order of the linear frequency. Therefore,
nonlinear effects must be important. Starting from the nonlinear
gyrokinetic equations of Frieman and Chen (1982) the perturbed
magnetic compressional component may be systematically isolated from
both the electrostatic component and the shear Alfvén component
assuming a cold electron population and a mode frequency less than the
parallel Alfvén frequency. Using a pressure closure scheme
consistent with the linear limit, a nonlinear single-field equation
similar to the Charney-Hasegawa-Mima equation (describing both
geostrophic flow and electrostatic drift waves) can be derived. In
the absence of growth or dissipation this equation conserves magnetic
energy and enstrophy (``current density''). The nonlinear
interactions spectrally redistribute the energy and enstrophy through
a dual cascade process in wavenumber space. Numerical simulations of
the single-field nonlinear equation will also be discussed.
DE: 7829 Kinetic waves and instabilities
DE: 7839 Nonlinear phenomena (4400, 6944)
DE: 7863 Turbulence (4490)
DE: 7868 Wave/wave interactions
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005