THE HELIOSPHERE IS A COMPLEX SYSTEM IN WHICH THE TRANSPORT OF MASS MOMENTUM AND ENERGY FROM LARGE TO SMALL SCALES AND THE EVENTUAL DISSIPATION OF ENERGY AS PLASMA HEAT SHAPES THE GLOBAL EVOLUTION. AS MODELING THE PHYSICAL PROCESS INVOLVED AT ALL SCALES IS NOT YET TRACTABLE WE STUDY IN THIS PROJECT THE MECHANISMS THAT ACT TO TRANSFER ENERGY BETWEEN ELECTROMAGNETIC FIELDS AND CHARGED PARTICLES USING A COMBINATION OF THEORETICAL MODELING AND IN SITU SOLAR WIND OBSERVATIONS. A NUMBER OF DIFFERENT PROCESSES HAVE BEEN PROPOSED WHICH MAY MEDIATE THIS ENERGY TRANSFER BUT THERE IS NO CLEAR SCIENTIFIC CONSENSUS AS TO WHICH OF THESE MECHANISMS OPERATE IN THE SOLAR WIND. EACH MECHANISM PREFERENTIALLY TRANSFERS ENERGY TO OR FROM PARTICLES WITH UNIQUE CHARACTERISTIC VELOCITIES AND MAY DOMINATE THE ENERGIZATION UNDER DIFFERENT SOLAR WIND AND PLASMA CONDITIONS. IN ORDER TO OBSERVATIONALLY DIFFERENTIATE BETWEEN THESE PROPOSED MECHANISMS WE WILL SEARCH FOR DISTINCT VELOCITY-SPACE SIGNATURES IN PARTICLE DISTRIBUTIONS AND ASSOCIATED ELECTRIC AND MAGNETIC FIELDS. THE NATURE OF THESE SIGNATURES WILL BE MOTIVATED BY ANALYTIC MODELS AND NUMERICAL SIMULATIONS WHICH COMBINED WITH SOLAR WIND OBSERVATIONS WILL ALLOW US TO ASSOCIATE PARTICULAR PLASMA AND SOLAR WIND PARAMETER REGIMES WITH THE OCCURRENCE OF PARTICULAR ENERGIZATION MECHANISMS. ..THE PROPOSED PROJECT IS DIVIDED INTO FOUR TASKS: .1) IDENTIFY INSTANCES OF PARTICULAR ENERGIZATION MECHANISMS OPERATING IN THE SOLAR WIND FROM IN SITU OBSERVATIONS USING CORRELATIONS BETWEEN VELOCITY-SPACE PARTICLE DISTRIBUTIONS AND ELECTROMAGNETIC FIELDS. .2) CHARACTERIZE THE PLASMA AND SOLAR WIND PARAMETERS FOR WHICH DIFFERENT ENERGIZATION MECHANISMS DOMINATE. .3) APPLY AN ALTERNATIVE STABILITY DETERMINATION METHOD TO SOLAR WIND OBSERVATIONS TO ASCERTAIN HOW UNSTABLE THE SOLAR WIND IS WHEN CONSIDERING MULTIPLE SOURCES OF FREE ENERGY. .4) IMPROVE EXISTING PARAMETERIZED MODELS FOR SOLAR WIND STABILITY USING THE ALTERNATIVE STABILITY DETERMINATION METHOD. ..CHARACTERIZING WHICH MECHANISMS ACT UNDER WHAT SOLAR WIND AND/OR PLASMA CONDITIONS WILL IMPROVE OUR UNDERSTANDING OF THE HELIOSPHERE AND ENABLE GLOBAL MODELS OF THIS SYSTEM TO INCORPORATE MORE PHYSICALLY MOTIVATED SMALL SCALE PHYSICS. .