2. Physics of Space Plasma

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2. Physics of Space Plasma

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2017 ASS-0926Let Uniform B, E=0, B in the z direction
2.2 SINGLE-PARTICLE MOTION
ExB drift No current
External force drift Current
The second adiabatic invariant The first adiabatic invariant
The total magnetic flux Φ enclosed by a drift surface is the third adiabatic invariant
• Characteristics of plasma: Quasi neutrality, collective behavior, good conductor.
• Phase space: 3D displacement + 3D velocity • The phase-space density function f(r, v, t) is also called the single-particle distribution function.
• Volume = dv dr = dvx dvy dvz dx dy dz • The differential phase-space volume = f(r, v, t) dv dr
2.3 COLLECTIONS OF PARTICLES
The zeroth moment of the distribution
The first moment of the distribution
The average kinetic energy per particle of s type in a unit volume of the plasma
The hydrostatic partial pressure
where N is the number of independent components of velocity, Ps is in Pascale (Pa), 1 Pa= 1N/m2.
V t
Maxwellian distribution
V t
Ionosphere 1012 103 10−5 10−3
Magnetosphere 107 107 10−8 102
Solar core 1032 107 -- 10−11
Solar wind 106 105 10−9 10
Interstellar medium 105 104 10−10 10
Intergalactic medium
Spacecraft (satellite) potential
characteristic time, characteristic length, collision frequency, mean free path, gyro frequency, gyro radius, plasma frequency, Debye length
Fp = 9000 N1/2, plasma frequency Fp in Hz, electron density N in #/cm3
Plasma frequency
http://abyss.uoregon.edu/
l >> rH (ν<<ω), Collision less plasma l << rH (ν>>ω), Collision plasma
Scale height
Hydrodynamics vs. Magnetohydrodynamics (MHD) Individual particle motions vs. Properties of a collection of many particles
Frozen-in flux
dt d !!!!!!