CHORUS WAVES PLAY A MAJOR ROLE IN SHAPING EARTH S RADIATION BELTS FROM ATMOSPHERIC LOSSES DRIVEN BY PITCH-ANGLE SCATTERING TO LOCAL ACCELERATION IN THE HEART OF THE OUTER BELT. THE AMPLITUDE AND ANGULAR DISTRIBUTION OF CHORUS WAVES ARE KEY INPUTS TO QUASI-LINEAR AND NON-LINEAR WAVE-PARTICLE INTERACTION MODELS. PRECISE MEASUREMENT AND KNOWLEDGE OF THESE PARAMETERS IS THEREFORE VITAL TO ACCURATE MODELING OF THE RADIATION BELTS. UNCERTAINTIES IN WHISTLER-MODE WAVE ELECTRIC FIELDS MEASURED BY VAN ALLEN PROBES HAVE BEEN UNCOVERED AND ATTRIBUTED TO ANTENNA SHEATH IMPEDANCE EFFECTS. UNDER SPECIFIC PLASMA CONDITIONS THE MEASURED ELECTRIC FIELD AMPLITUDE WAS REPORTED TO BE AS LOW AS 10% OF THAT PREDICTED BY THEORY WITH DISCREPANCIES INCREASING WITH DECREASING PLASMA DENSITY. TO DATE THIS TYPE OF ANALYSIS HAS ONLY BEEN PERFORMED ON VAN ALLEN PROBES OBSERVATIONS BUT THESE EFFECTS ARE CERTAIN TO IMPACT OTHER SPACECRAFT MEASUREMENTS USING SIMILAR INSTRUMENTATION. KNOWLEDGE OF THESE UNCERTAINTIES IS CRUCIAL BOTH FOR QUANTIFYING THE IMPACT OF OBLIQUE QUASI-ELECTROSTATIC CHORUS WAVES ON RADIATION BELT PARTICLES AS WELL UNDERSTANDING THE EFFECT ON PARAMETERS DERIVED FROM ELECTRIC FIELD OBSERVATIONS INCLUDING THE POYNTING VECTOR. WHISTLER-MODE WAVE ELECTRIC FIELD MEASUREMENT UNCERTAINTIES WILL BE INVESTIGATED WITH MMS SPACECRAFT DATA USING THE SAME METHOD AS APPLIED TO VAN ALLEN PROBES. THAT IS COMPARING THE MEASURED ELECTRIC FIELD TO THAT PREDICTED USING THE OBSERVED MAGNETIC FIELD AND THE WHISTLER-MODE DISPERSION RELATION. THE MMS ORBIT EXTENDING OUT TO LARGER RADIAL DISTANCES AND HENCE LOWER PLASMA DENSITIES MAKES IT IDEAL FOR FURTHER EXPLORING ELECTRIC FIELD MEASUREMENT UNCERTAINTIES IN THE LOW-DENSITY CASE. THE IMPACT OF THESE UNCERTAINTIES WILL BE ASSESSED FOR VAN ALLEN PROBES AND MMS THROUGH COMPARISONS OF ELECTRIC FIELD WAVE AMPLITUDE AND THE ANGULAR DISTRIBUTIONS OF WAVE NORMAL ANGLE AND POYNTING VECTOR DIRECTION. NO SUCH STUDIES HAVE DIRECTLY ADDRESSED THE IMPACT ON THESE PARAMETERS WHICH ARE CRUCIAL FOR UNDERSTANDING ENERGY DISPERSION IN THE MAGNETOSPHERE AND ALSO FOR THE ACCURACY OF AMPLITUDE AND WAVE NORMAL ANGLE DISTRIBUTIONS USED IN RADIATION BELT MODELING. AS SUCH THE PROPOSED WORK DIRECTLY CONTRIBUTES TOWARDS IMPROVING THE CHARACTERIZATION OF PHYSICAL PROCESSES IN THE MAGNETOSPHERIC ENVIRONMENT. THE SCIENCE OBJECTIVE OF THIS PROPOSAL IS TO: CHARACTERIZE THE ANGULAR DISTRIBUTION OF POYNTING VECTOR DIRECTION AND WAVE NORMAL ANGLE FOR WHISTLER-MODE CHORUS WAVES AND QUANTIFY HOW UNCERTAINTIES IN ELECTRIC FIELD OBSERVATIONS MAY IMPACT THESE DISTRIBUTIONS. TO DO THIS THE FOLLOWING QUESTIONS WILL BE ANSWERED: Q1) WHAT ARE THE CHARACTERISTICS OF THE ANGULAR DISTRIBUTION OF BOTH POYNTING VECTOR AND WAVE NORMAL ANGLE FOR CHORUS WAVES OBSERVED BY VAN ALLEN PROBES AND MMS HOW DO THESE DISTRIBUTIONS COMPARE AND HOW DO THEY VARY OVER THE ORBITS SAMPLED BY EACH MISSION? Q2) HOW DOES THE CHORUS WAVE ELECTRIC FIELD OBSERVED BY MMS COMPARE TO THE ELECTRIC FIELD PREDICTED FROM THE WHISTLER-MODE DISPERSION RELATION AND THE MEASURED MAGNETIC FIELD? Q3) HOW DO DISCREPANCIES BETWEEN THE OBSERVED AND THEORETICALLY PREDICTED ELECTRIC FIELD IMPACT PARAMETERS DERIVED FROM VAN ALLEN PROBES AND MMS OBSERVATIONS SUCH AS POYNTING FLUX MAGNITUDE AND POYNTING VECTOR ORIENTATION? MMS FIELDS AND FPI DATA AND VAN ALLEN PROBES EMFISIS AND EFW DATA WILL BE USED IN THE PROPOSED WORK. THIS PROPOSAL DIRECTLY CONTRIBUTES TOWARDS THE 2013-2022 DECADAL SURVEY IN SOLAR AND SPACE PHYSICS SCIENTIFIC GOALS TO 'DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS' AND TO 'DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE' IN ADDITION TO THE 2014