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Kinetic Theory
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Particle Distribution Function
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Density Function ns Number density, mass density, charge density
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The Boltzmann Equation: time variation of a distribution function
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Total Derivative in Phase Space
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Homework Problem 3.6, 3.7, 3.8
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Examples of Distribution Functions
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Maxwellian Distribution Functions
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One-dimensional Maxwellian, cont’d
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Thermal speed
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Equilibrium Distribution
charge x voltage = energy
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Velocity Moments
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Bulk flow velocity
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Pressure tensor
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Scalar pressure
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Heat Flux
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Continuity equation: 0th moment of B-equation
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Momentum Equation: 1st moment of B-equation
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The momentum equation
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Pressure Gradient Force
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Pressure as Thermal Energy Density
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Charge and Current Densities
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Moments Measurements in Space Physics
Particle detector measures electric current produced by the charged particles The electric field current, count-rate, is converted to number of density flux according to calibration The flux can be converted to distribution function The detector can select the energy range with energy resolution, as well as type of the particle species Each detector has a finite field angle which determines the spatial resolution The detector(s) scan over directions Fluxes from all energy channels and all looking directions can be added together. Moment factor can be added in the integration process to obtain moments, which are used as macroscopic quantities, such as density, velocity, temperature, (temperature) anisotropy Satellite charge is a major problem in deriving correct distribution function In the existence of multiple populations, “moments” may mean different things. Distribution functions have to be examined in this case.
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