13:45 〜 14:00
[PEM10-11] Numerical analysis on non-local and nonlinear evolution of auroral fine structures in the magnetosphere-ionosphere coupling
キーワード：オーロラ、アルヴェン波、磁気圏ｰ電離圏結合系
Our previous works on the feedback instability in the magnetosphere-ionosphere (M-I) coupling system under a local approximation have revealed that the Kelvin-Helmholtz (K-H) type instability driven by enhanced E×B flow shear deforms auroral arc-like structures and leads to vortex formation followed by turbulence transition. However, global properties of the auroral growth have not been understood well except for a few basic properties of auroral arc structure formation elongated in the longitudinal direction.
In this study, we have performed a nonlinear simulation of the feedback instability in a non-local M-I coupling with the dipole field configuration to investigate nonlinear evolution of auroral fine structures by means of a novel numerical simulation code for a set of the reduced magnetohydrodynamic equations with a non-uniform kinematic viscosity in the magnetosphere and the two-fluid equations in the ionosphere. The simulation results clearly demonstrate transition to a turbulent state after convective growth of auroral fine structures and the succeeding K-H type instability. In addition, we have observed expansion of auroral turbulent structures broadening into the latitudinal directions as well as in the wave number spectrum in the nonlinear stage.
In this study, we have performed a nonlinear simulation of the feedback instability in a non-local M-I coupling with the dipole field configuration to investigate nonlinear evolution of auroral fine structures by means of a novel numerical simulation code for a set of the reduced magnetohydrodynamic equations with a non-uniform kinematic viscosity in the magnetosphere and the two-fluid equations in the ionosphere. The simulation results clearly demonstrate transition to a turbulent state after convective growth of auroral fine structures and the succeeding K-H type instability. In addition, we have observed expansion of auroral turbulent structures broadening into the latitudinal directions as well as in the wave number spectrum in the nonlinear stage.