《空间物理学》课程教学资源（PPT课件讲稿）空间等离子体和单粒子的运动、Kinetic Theory和MHD简介

空间物理学(D 2空间等离子体和单 粒子的运动、 Kinetic Theory和MHD简介

1 2.空间等离子体和单 粒子的运动、Kinetic Theory 和 MHD 简介 空间物理学（I）

Outline ■等离子体的定义 ■磁矩守恒量 ■ Debye长度和等离子体 磁镜效应 的特性 ■ Trapped particles ■空间等离子体 ■辐射带 ■电离层 ■单个带电粒子的运动■极光的产生 ■回旋波 ■磁冻结效应 Guiding center motion■ Kinetic theory简介 ■MHD简个

Outline: ◼ 等离子体的定义 ◼ Debye长度和等离子体 的特性 ◼ 空间等离子体 ◼ 单个带电粒子的运动 ◼ 回旋波 ◼ Guiding center motion ◼ 磁矩守恒量 ◼ 磁镜效应 ◼ Trapped particles ◼ 辐射带 ◼ 电离层 ◼ 极光的产生 ◼ 磁冻结效应 ◼ Kinetic theory简介 ◼ MHD简介 2

等离子体 ■等离子体的定义: 由自由电子和自由离子组成的集合体(气体),其正 负电荷数目相同。在平均作用的意义上,等离子体对外呈 现电中性。 等离子体的直接特性: 自由离子和自由电子占主导地位(即 带电粒子所受到的势能远小于粒子热运动 的动能),随机的热运动克服库仑势

3 等离子体 ◼ 等离子体的定义: 由自由电子和自由离子组成的集合体（气体），其正 负电荷数目相同。在平均作用的意义上，等离子体对外呈 现电中性。 等离子体的直接特性： 自由离子和自由电子占主导地位（即 带电粒子所受到的势能远小于粒子热运动 的动能），随机的热运动克服库仑势

Property Gas Plasma Electrical Usually very high Conductivity Air is an excellent insulator until it breaks down into For many purposes, the conductivty of a plasma may plasma at electric field strengths above 30 kilovolts pe be treated as infinite Two or three g species All gas particles behave in a similar way, influenced by gravity and by collisions with one another Electrons, ions, protons and neutrons can be ished by the sign an their charo that they behave independently in many circumst with different bulk velocities and temperatures, allowing phenomena such as new types of waves and Velocity Maxwellian Often non-Maxwellian distribution Collisions usually lead to a Maxwellian velocity Collisional interactions are often weak in hot plas and external forcing can drive the plasma far from fast particles equilibrium and lead to a significant population of lly fast particl Interactions Binary Collective Two-particle collisions are the rule, three-body Waves, or organized motion of plasma, are very collisions extremely rare important because the particles can interact at long ranges through the electric and magnetic forces http://en.wikipediaorg/wiki/plasma%28physIcs%29

4 Property Gas Plasma Electrical Conductivity Very low Air is an excellent insulator until it breaks down into plasma at electric field strengths above 30 kilovolts per centimeter. Usually very high For many purposes, the conductivity of a plasma may be treated as infinite. Independently acting species One All gas particles behave in a similar way, influenced by gravity and by collisions with one another. Two or three Electrons, ions, protons and neutrons can be distinguished by the sign and value of their charge so that they behave independently in many circumstances, with different bulk velocities and temperatures, allowing phenomena such as new types of waves and instabilities. Velocity distribution Maxwellian Collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very few relatively fast particles. Often non-Maxwellian Collisional interactions are often weak in hot plasmas and external forcing can drive the plasma far from local equilibrium and lead to a significant population of unusually fast particles. Interactions Binary Two-particle collisions are the rule, three-body collisions extremely rare. Collective Waves, or organized motion of plasma, are very important because the particles can interact at long ranges through the electric and magnetic forces. http://en.wikipedia.org/wiki/Plasma_%28physics%29

分离的正离子和电子是否会在电场力的库仑 相互作用下结合成电中性原子或者分子?频繁的 带电粒子碰撞对等离子体的影响是什么? Plasma lamt Seehttp://en.wikipedia.org/wiki/plasma%28physicS%29

5 See http://en.wikipedia.org/wiki/Plasma_%28physics%29 Plasma lamp 分离的正离子和电子是否会在电场力的库仑 相互作用下结合成电中性原子或者分子？频繁的 带电粒子碰撞对等离子体的影响是什么？

什么样的条件使得等离子体稳定存在? 1保持电中性 2自由粒子的存在 3发生碰撞的几率低

6 什么样的条件使得等离子体稳定存在？ 1.保持电中性 2.自由粒子的存在 3.发生碰撞的几率低

德拜屏蔽( Debye Shielding) 等离子体存在一个特征长度,在此特征长 度以外,带电粒子间库仑势场因为屏蔽效应迅 速减弱。这个特征长度定义为 Debyelength。 kT

7 德拜屏蔽(Debye Shielding) 等离子体存在一个特征长度，在此特征长 度以外，带电粒子间库仑势场因为屏蔽效应迅 速减弱。这个特征长度定义为Debye length。 2 0 0 n e kTe D   =

Magneti confinement nfinement fusio fusio olor core 10 solar corona Solar wind , Ne 10 Int erst ellar space fluorescent light Aurora Flat plasmas fo exist. 10310 5 10151 0 21 102710 Number Density(Charged Particles/m3) Copyright 1996 Contemp orary Physics Education Project of doe fusion labs, NASa, and Steve albe Debye Length由温度和带电粒子的密度共同决定

8 Debye Length由温度和带电粒子的密度共同决定

Debye and Coulomb potential Debye and Coulomb potential 库仑势 4兀c 德拜势 tE repo 4 Distance

9 Debye and Coulomb potential r Q 4 0 1    = exp( ) 4 1 0 D r r Q     = − 库仑势 德拜势

德拜屏蔽( Debye Shielding) 统计物理指出自由粒子在相空间*的分布大致如下 fe(v=n m,,-+g rhr// kT 相空间指(Vx。 v..rr2)组成的坐标空间

10 德拜屏蔽(Debye Shielding) 统计物理指出自由粒子在相空间*的分布大致如下：         +  −         = e e e e k T m V q k T m n 2 2 2 1 3 e 0 exp 2 f (v)  *相空间指（vx , vy , vz , rx , ry , rz）组成的坐标空间