Restoration of particle pitch angle distribution functions by a maximum entropy algorithm
Abstract
A technique is presented with which to analyze particle flux data in order to resolve features in the pitch angle distribution which are smaller than the angular response width of the detector. This process uses a large number of data points which overlap in pitch angle to construct a maximum entropy criterion for the true angular distribution at constant energy. Statistical arrors in the measured fluxes are allowed by the inclusion of a Chisquared constraint in the calculation. Example electron distribution functions computed from SCATHA observation show loss cone gradients with widths of less than two degrees, with an instrument response of approximately six degrees. Models of both the original and the restored distributions are constructed as sums of biMaxwellians. The differences in the electrostatic stability of these models due to changes in the velocity gradients are discussed. This analysis may have applications for estimating beam, conic, and loss cone features in particle velocity distributions throughout the ionosphere and magnetosphere with significant consequences for waveparticle interactions.
 Publication:

Unknown
 Pub Date:
 November 1986
 Bibcode:
 1986rppa.rept.....R
 Keywords:

 Algorithms;
 Distribution Functions;
 Maximum Entropy Method;
 Particle Density (Concentration);
 Pitch (Inclination);
 Angular Distribution;
 Earth Ionosphere;
 Earth Magnetosphere;
 Electrostatic Charge;
 MaxwellBoltzmann Density Function;
 Stability;
 Velocity Distribution;
 Atomic and Molecular Physics