THIS PROJECT WILL INVOLVE BOTH THE ANALYSIS OF IN SITU OBSERVATIONS AND THE DEVELOPMENT OF SIMULATIONS. WE WILL STUDY MEASUREMENTS MADE WITH VARIOUS INSTRUMENTS ON THE HELIOS WIND AND ACE SPACECRAFT. FOR THE MOST PART WE WILL RETRIEVE THESE DATA FROM CDAWEB BUT (COURTESY OF PROF. ECKART MARSCH) WE WILL ALSO UTILIZE ELECTRON AND ION DISTRIBUTION MEASUREMENTS FROM HELIOS. FOR OUR SIMULATIONS WE WILL EMPLOY LANGEVIN MODEL/COLLISIONAL HYBRID EXPANDING BOX CODE. IN GENERAL HYBRID SIMULATION CODES TREAT IONS SELF-CONSISTENTLY AS KINETIC PARTICLES FOR WHICH THE FULL EQUATION OF MOTION IS SOLVED BUT TREAT ELECTRONS AS A MAGNETIZED FLUID THAT IS ASSUMED TO BE ISOTHERMAL AND (IN MOST CASES) MASSLESS. NONLINEAR EFFECTS OF ION-CYCLOTRON RESONANT INTERACTIONS ARE THEREFORE AUTOMATICALLY INCLUDED. THE EFFECTS OF THE IONS ON THE WAVE DISPERSION RELATION AND THE EFFECT OF THE WAVES ON THE ION DISTRIBUTION FUNCTIONS ARE ALSO TREATED IN A FULLY NON-LINEAR SELF-CONSISTENT MANNER. THE HYBRID EXPANDING BOX (HEB) MODEL WAS DEVELOPED TO INVESTIGATE THE INTERACTION BETWEEN SOLAR WIND IONS THE LOCAL WAVE FIELD AND SOLAR-WIND EXPANSION. COULOMB COLLISIONS IN WEAKLY COLLISIONAL PLASMAS ARE ESSENTIALLY KINETIC PHENOMENON AND NEED A KINETIC TREATMENT. IN PARTICLE-IN-CELL CODES THE COULOMB COLLISIONS ARE OFTEN MODELLED BY STOCHASTIC ENERGY AND MOMENTUM EXCHANGE BETWEEN RANDOMLY PAIRED PARTICLES. AN ALTERNATIVE POSSIBILITY IS TO INCLUDE COULOMB COLLISIONS IN PARTICLE-IN-CELL CODES USING ONE-PARTICLE STOCHASTIC FORCING GIVEN BY THE LANGEVIN EQUATION CORRESPONDING TO THE FOKKER-PLANCK COLLISION EQUATION. THIS MODEL WAS DEVELOPED FOR BI-MAXWELLIAN SCATTERS BY HELLINGER AND TRAVNICEK IN VIEW OF LARGE PARTICLE TEMPERATURE ANISOTROPIES OBSERVED IN THE SOLAR WIND.

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