ICS-13 Abstract View

 

Alfvenic turbulence in auroral magnetosphere-ionosphere coupling
Watanabe, T.-H., watanabe.tomohiko@nagoya-u.jp (1)
Kaneyama, M., kaneyama@p.phys.nagoya-u.ac.jp (1)
Maeyama, S., smaeyama@p.phys.nagoya-u.ac.jp (1)
The feedback instability is known to be destabilized in the magnetosphere-ionosphere (M-I) coupling, when the magnetospheric convection velocity exceeds a critical value. During the instability growth, the shear Alfven waves are amplified with enhancement of the field aligned current and the ionospheric density perturbations. Development of the local field-aligned current circuit is associated with spontaneous excitation of auroral arc structures and electron precipitation.

The feedback instability has widely been investigated both in the linear and the weak nonlinear regimes while the full nonlinear study is limited so far. Nonlinear saturation of the feedback instability growth is discussed in terms of the secondary instability [1,2], where the Kelvin-Helmholtz type mode is generated by a sheared ExB flow. Recently, we have developed a new nonlinear simulation code for the M-I coupling, and applied it to investigate a long-time evolution of the feedback instability.

In the fully nonlinear stage of the feedback instability, we have found transition to turbulence through the M-I coupling [2], where the energy equipartition is observed in the Alfvenic turbulence. During the tradition phase, auroral vortices are also observed in terms of the ionospheric density enhancement and depletion. The obtained results provide a novel theoretical understanding on spontaneous generation of Alfvenic turbulence observed in auroral regions.


[1] T.-H. Watanabe, Phys. Plasmas 17, 022904 (2010).
[2] T.-H. Watanabe, H. Kurata, and S. Maeyama, New J. Phys. 18, 125010 (2016).
(1) Department of Physics, Nagoya University, Nagoya 464-8602, Japan