Density Function ns Number density, mass density, charge density
Homework Problem 3.6, 3.7, 3.8
charge x voltage = energy Equilibrium Distribution
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.