Lower-Hybrid Drift Instability (LHDI)

1. Lower-Hybrid Drift Instability (LHDI) Summary and Simulation Results

2. Summary of LHDI Magnetic Reconnection and instabilities in current sheet z y-z: current sheet plane x-z: reconnection plane B J=μ0-1 rot B y x

3. Summary of LHDI • The LHDI is driven by the diamagnetic current in the presence of inhomogeneities in the density and magnetic field • Fastest growing modes

4. Summary of LHDI • Historically, LHDI has attracted much attention in as a source of anomalously large resistivity observed in laboratory device. • Subsequently and quite naturally, LHDI was suggested as a source of anomalous resistivity in the magnetotail.

5. Simulation of LHDI Early Results • Nonlinear phase of instabilities in the current sheet and their contribution to the reconnection cannot fully understood except by means of simulations. • However, … Current computer simulations face many practical hurdles in dealing with realistic situation, e.g. The difficulty of implementing the realistic proton-to-electron mass ratio. Besides, it is difficult to use the simulations carried out under highly idealized situations and extrapolate to the real situations.

6. Simulation of LHDI Early Results • Winske [Phys. Fluids 1981] describe a longer wavelength EM mode which develops in the central region after the saturation of fastest growing LHDI. Characteristic wave vector: • Tanaka [J. Geophys. Res. 1981]

7. Summary of LHDI • Despite earlier suggestion that LHDI may play a key role in magnetotail reconnection physics, it was soon realized that LHDI is stabilized as a result of increasing local beta. • However, efforts were made to show that LHDI is not completely stabilized near the neutral sheet in a magnetotail-like geometry.

8. Simulation of LHDI Recent Results Daughton [Phys. Plasmas 2003] 1. Fastest growing modes: ES waves are confined to the edge of sheet 0.5<|x/L|<3.5. Bzw 0.5 <|x/L|<2..5 Note: For a given wavelength, there are actually multiple unstable lower-hybrid modes. Daughton 2003 Phys. Plasmas

9. Simulation of LHDI Recent Results 2. Long wavelength modes ES waves are still confined to the edge EM waves are localized about the center. γ/Ωci=0.84 Note: For a given wavelength, there are actually multiple unstable lower-hybrid modes. Daughton 2003 Phys. Plasmas

10. Simulation of LHDI Recent Results Fastest growing LHDI have saturated ES waves are confined to the edge of sheet. Bz 0.5<|x/L|<1.0 Ey 0.5<|x/L|<4.0

11. Simulation of LHDI Recent Results

12. Simulation of LHDI Recent Results USTC School of Earth and Space Sci. • 对电流剖面的影响：对不同厚度的电流片，可形成中心增强的电流片以及双峰电流片。 • 对电子的加热：低混杂漂移不稳定性加热电子，并造成温度各项异性，垂直磁场方向温度大于平行电场温度。 Ricci 2005 Phys. Plasmas

13. Simulation of LHDI Recent Results Lower-hybrid fluctuations Crossing Noncrossing Example of scattering Crossing USTC School of Earth and Space Sci. Daughton 2004 PRL

14. Simulation of LHDI Recent Results D=1.0c/ωpi Ti/Te=8 (ion carry most current) Electron E×B drift and generate electron vortices The ion flow pattern in the current sheet is globally modulated by KHI, nonlinear evolution of KHI can permit LHDI to be unstable at the edge of KH vortexes. No electric field right at the neutral can be found. LHDI (electron scale) CSKI (hybrid scale) KHI (MHD scale) Shinohara 2001.

15. Simulation of LHDI Recent Results USTC School of Earth and Space Sci. • 与三维磁重联的耦合 • 包含低混杂漂移不稳定 • 性的三维全粒子模拟可 • 在短时间内快速触发磁 • 重联。 Scholer 2003 Phys. Plasmas

16. Simulation of LHDI Recent Results

17. Simulation of LHDI Recent Results