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Magnetic Reconnection — Questions & Challenges Xiaogang Wang School of Physics, Peking University IFTS, Zhejiang University Sept 23 2007, Suzhou, China

Magnetic Reconnection — Questions & Challenges

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Magnetic Reconnection — Questions & Challenges. Xiaogang Wang School of Physics, Peking University IFTS, Zhejiang University Sept 23 2007, Suzhou, China. OUTLINE. What we have known What we don’t know Possible answers Brief summary. What we have known. Hall effect physics - PowerPoint PPT Presentation

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Page 1: Magnetic Reconnection — Questions & Challenges

Magnetic Reconnection— Questions &

Challenges

Xiaogang Wang

School of Physics, Peking UniversityIFTS, Zhejiang University

Sept 23 2007, Suzhou, China

Page 2: Magnetic Reconnection — Questions & Challenges

OUTLINE

• What we have known• What we don’t know• Possible answers• Brief summary

Page 3: Magnetic Reconnection — Questions & Challenges

What we have known

• Hall effect physics– Alfven frequency whistler waves– Quadruple field– Fast reconnection rate 0.01 ~ 0.2VA

– Layer width of reconnecting field ~ di

– Electrical potential well on separatrix

Page 4: Magnetic Reconnection — Questions & Challenges

What we have known

• In question– Layer length of reconnecting field ~

(diL)1/2

– Reconnecting rate ~ (di/L)1/2

– Electron density dip on separatrix (numerically observed)

– Lower hybrid oscillations (observed) – Electron Alfven speed disturbance

(observed)

Page 5: Magnetic Reconnection — Questions & Challenges

What we have known

•3D reconnection features– The existence of magnetic nulls

(observed)–Null-null line (Separator,

observed)–Spines and fans (observed)– Lower hybrid waves on the

separator (observed)

Page 6: Magnetic Reconnection — Questions & Challenges

What we have known

•3D reconnection features– Electron density peak on separato

r (observed)– Electrical potential well on separa

tor (observed)– Langmuir oscillation near separat

or (observed)

Page 7: Magnetic Reconnection — Questions & Challenges

What we don’t know

• 电子惯性区中的波动,特别是低杂波的激发与传播;

• 电子惯性区(包括分形线)中的密度 sh 上升?下降? —— 原因及后果;

• 重联过程中的电子加热机制?• 电子 Alfven 波的存在?• Electron hole 的产生原因以及电子声

波是否存在?

Page 8: Magnetic Reconnection — Questions & Challenges

What we don’t know

• 电子压强梯度张量非对角项的贡献;• 重联率的 Scaling 的继续研究;• 电子惯性是否对重联率有贡献?• Whistler or 离子波的贡献、观测及其

与其他模式(比如 LHW )的耦合? • 剪切流对重联结构和重联率的影响

Page 9: Magnetic Reconnection — Questions & Challenges

What we don’t know

• Hall 四极分布是否就是 Whistler or Alfven 频率 whistler 的驻波表现?

• 边界驱动对无碰撞磁重联的影响?

Page 10: Magnetic Reconnection — Questions & Challenges

What we don’t know (3D)

• 3D 重联中的 Hall 四极分布问题?• Separator 上的电子加热机制及其与

2D 理论的对比?• Anti-parallel reconnection vs. Co

mponent reconnection ( 理论、观测上,对重联率的影响 )?

Page 11: Magnetic Reconnection — Questions & Challenges

What we don’t know (3D)

• Null 以及 Null-null line 的产生机制( X-line 不稳定导致 null pair 产生是否是唯一机制)?

• 3D 重联的动力学理论( Theory of 3D reconnection dynamics )

• 单个 Null 与 Null pair 对重联发生和重联率大小的影响

Page 12: Magnetic Reconnection — Questions & Challenges

Possible answers

• 应用回旋动力学理论研究电子压强梯度张量非对角项的贡献;

• 重联率 Scaling 的实验研究;• 双流体理论、回旋动力学理论中 Whistler or Alfv

en 频率 whistler 与其它模式(如 LHW )的耦合;

• 剪切流及 Alfven 共振研究 • 边界驱动无碰撞磁重联研究( Hall MHD + Hybri

d codes)

Page 13: Magnetic Reconnection — Questions & Challenges

Possible answers

• Separator 上的磁镜效应及电子加速与加热机制

• Anti-parallel reconnection — Component reconnection :一个过程的两种表现形式;统计研究

Page 14: Magnetic Reconnection — Questions & Challenges

SUMMARY

• Hall effects well understood• Electron dynamics not• 3D features getting attentions

• MHD & Magnetic reconnection FTP (PKU, ZJU, NAOC, USTC, DLUT)

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