THE PLASMASPHERE IS A TORUS OF COLD PLASMA SURROUNDING EARTH. ITS SHAPE IS DYNAMICALLY DETERMINED BY A BALANCE OF SOLAR WINDDRIVEN CONVECTION CO-ROTATION WITH EARTH'S MAGNETIC FIELD AND REFILLING FROM IONOSPHERIC OUTFLOW. HISS EFFICIENTLY SCATTERS ELECTRONS FACILITATING THEIR LOSS TO THE ATMOSPHERE AND THEREBY PLAYING A SIGNIFICANT ROLE IN SHAPING INNER MAGNETOSPHERIC ELECTRON POPULATIONS INCLUDING THE RADIATION BELTS. FOR THIS REASON ELECTRON LOSS BY HISS WAVE SCATTERING IS A CRITICAL COMPONENT OF COMPUTATIONAL MODELS OF THE INNER MAGNETOSPHERE. SUCH MODELS INCLUDE THIS IMPORTANT PHYSICAL PROCESS USING OBSERVATIONS IN THE FORM OF STATISTICAL MAPS OF HISS WAVE CHARACTERISTICS (E.G. INTENSITY SPECTRAL SHAPE) PARAMETERIZED BY LOCATION WITHIN THE MAGNETOSPHERE AND GEOMAGNETIC ACTIVITY LEVEL. DESPITE OF THE LONG HISTORY OF INNER MAGNETOSPHERE RESEARCH THE VAN ALLEN PROBES MISSION HAS REVEALED NEW ASPECTS OF HISS. IN PARTICULAR IT WAS SHOWN THAT HISS EXTENDS TO LOWER FREQUENCIES THAN WAS PREVIOUSLY ASSUMED. THIS LOW FREQUENCY HISS HAS A DIFFERENT SPATIAL DISTRIBUTION THAN HIGHER FREQUENCY HISS. LOW FREQUENCY HISS AND HISS LEAKING OUT FROM THE PLASMASPHERE (EXOHISS) BOTH LEAD TO INCREASED EFFICIENCY OF HIGH ENERGY ELECTRON SCATTERING WHEN INCLUDED IN MODELS OF INNER MAGNETOSPHERIC ELECTRON DYNAMICS. ALSO RECENT STUDIES HAVE DEMONSTRATED THAT THE SPATIAL DISTRIBUTION OF HISS WAVE POWER IS ORGANIZED WITH RESPECT TO THE PLASMAPAUSE LOCATION (THE OUTER EDGE OF THE PLASMASPHERE). THIS STRONG CONSTRAINT IS AVERAGED AWAY BY TRADITIONAL L-SHELL PARAMETERIZATIONS OF HISS WHICH PRODUCE BLURRED PHYSICALLY UNREALISTIC STATISTICAL HISS INTENSITY MAPS. THE SCIENTIFIC OBJECTIVE OF THE PROPOSED WORK IS TO QUANTIFY THE IMPORTANCE OF THESE ASPECTS OF HISS PHYSICS CURRENTLY MISSING FROM PREDICTIVE MODELING ON ELECTRON DYNAMICS IN THE INNER MAGNETOSPHERE. SCIENCE QUESTIONS: [1] WHAT ARE THE OBSERVED DISTRIBUTIONS OF HISS AMPLITUDE SPECTRAL SHAPE AND WAVE NORMAL ANGLE WHEN INCLUDING LF HISS EXOHISS AND ORGANIZATION BY PLASMAPAUSE LOCATION? [2] HOW ARE THE PROPERTIES OF INNER MAGNETOSPHERIC ELECTRON POPULATIONS INFLUENCED BY THESE `MISSING' ASPECTS OF HISS INCLUDING ELECTRON PITCH ANGLE DISTRIBUTIONS SPECTRUM AND LIFETIMES? [3] DOES INCLUSION OF THESE `MISSING' HISS ASPECTS IMPROVE THE ACCURACY OF MODELED ELECTRON DYNAMICS IN THE INNER MAGNETOSPHERE? METHODOLOGY: [1] USE VAN ALLEN PROBES DATA TO PRODUCE COMPREHENSIVE STATISTICAL MAPS OF HISS PROPERTIES (EXPLICITLY INCLUDING LF HISS EXOHISS AND ORGANIZATION BY PLASMAPAUSE LOCATION) OPTIMIZED FOR USE BY PREDICTIVE INNER MAGNETOSPHERIC MODELS. [2] RUN SENSITIVITY SIMULATIONS USING THE VERSATILE ELECTRON RADIATION BELT (VERB) CODE FOR INNER MAGNETOSPHERIC PREDICTIVE MODELING INCLUDING THE 'MISSING' HISS ASPECTS ONE BY ONE THEN ALL TOGETHER. ELECTRON PROPERTIES (E.G. PITCH ANGLE DISTRIBUTION SPECTRA LIFETIME) RETURNED BY THESE SIMULATIONS ARE TO BE COMPARED WITH SIMULATIONS USING HISS PARAMETERIZATIONS FROM PREVIOUS WORKS. [3] USE THE VERB CODE TO MODEL INNER MAGNETOSPHERIC ELECTRON DYNAMICS FOR A RANGE OF OBSERVED GEOMAGNETIC EVENTS WHERE EACH EVENT IS MODELED USING HISS PARAMETERIZATIONS DEVELOPED PRIOR TO THIS STUDY AND USING HISS PARAMETERIZATIONS DEVELOPED BY THIS STUDY. WE WILL THEN QUANTIFY THE DIFFERENCES BETWEEN BOTH MODEL RESULTS AND VAN ALLEN PROBES OBSERVATIONS FOR EACH MODELED EVENT. THIS RESEARCH FOCUSES ON THE DECADAL SURVEY GOAL: [1] DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS.