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- 核融合力学部門 高エネルギープラズマ分野
小菅 佑輔
[ セミナー ]
Shear instabilities in incompressible magnetohydro- dynamics
| 日 時 | 2018 年 3 月 6 日（火） 14 時 50 分 ～ 16 時 20 分 |
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| 場 所 | 九州大学総合理工学府 Ｈ棟 ２階講義室 * アクセス案内はこちら |
| 題 目 | Shear instabilities in incompressible magnetohydrodynamics |
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| 講演者 | Dr. Julian Mak (Oxford University, Department of Physics) |
| Abstract | The problem of shear flow instability and nonlinear development in incompressible homogeneous 2d MHD is revisited. The instability mechanism is re-interpreted as a pair of resonating vorticity waves, analogous to barotropic/baroclinic instabilities that occurs in more conventional rotating stratified fluid dynamics, in contrast to an explanation based on negative energy waves. The subsequent nonlinear development of said instabilities manifest as Kelvin-Helmholtz billows, but the eddy may transition to turbulence and disrupt the mean state through magnetic feedbacks, when it is otherwise nonlinearly stable in the absence of a magnetic field. An analytical estimate based on the physical mechanism for this transition is given, supported by appropriate direct numerical simulations. |
