OVERALL GOAL: WE PROPOSE TO INVESTIGATE THE RELATIVE ROLES OF COULOMB COLLISIONS LOCALLY ENHANCED CONVECTION ELECTRIC FIELDS AND PLASMA WAVES DAMPING IN TRANSFERRING ENERGY FROM THE RING CURRENT TO THE IONOSPHERE-THERMOSPHERE USING A COMBINATION OF IN SITU SATELLITE PARTICLE AND FIELD DATA IN THE INNER MAGNETOSPHERE AND SUBAURORAL RED-LINE SAR ARC EMISSIONS AS A DIAGNOSTIC OF THESE PROCESSES. MOTIVATION: OBSERVATIONS OF SAR ARCS (SPECTRALLY PURE 630.0 NM EMISSION) BY ALL-SKY IMAGERS (ASIS) SUGGEST THAT THEY ARE MORE COMPLICATED THAN PREVIOUSLY THOUGHT WITH INCONSISTENCIES BETWEEN OBSERVATIONS AND PUBLISHED THEORY. THE OCCURRENCE OF LOCALIZED ENHANCED POLEWARD-DIRECTED SUB-AURORAL ELECTRIC FIELDS (TERMED SAPS OR SAID) PRESENT A POSSIBLE MECHANISM FOR THE PRODUCTION OF SAR ARC EMISSIONS PREVIOUSLY NOT CONSIDERED DUE TO LACK OF OBSERVATIONS AND UNDERSTANDING. WE PROPOSE TO CONDUCT A SYSTEMATIC STUDY OF INNER MAGNETOSPHERIC PARTICLE AND FIELD OBSERVATIONS USING DATA FROM THE VAN ALLEN PROBES (VAP) AND THEMIS SPACECRAFT ALONG WITH SUB-AURORAL IONOSPHERIC DATA OF SAR ARCS FROM ASIS AND CO-LOCATED F-REGION DATA FROM DMSP SPACECRAFT AND MILLSTONE HILL INCOHERENT SCATTER RADAR. SCIENCE QUESTIONS: WE WILL LOOK AT LOSS OF RING CURRENT ENERGY VIA COULOMB COLLISIONS OF RING CURRENT IONS WITH COLD PLASMASPHERIC ELECTRONS AND STUDY THE EXTENT TO WHICH SAPS ELECTRIC FIELDS PLAY A ROLE IN PRODUCING SAR ARC EMISSIONS. THE SPECIFIC SCIENCE QUESTIONS ARE: (A) HOW ARE SAR ARCS RELATED TO THE RING CURRENT AND PLASMASPHERE? (B) WHAT ROLE DO COULOMB COLLISIONS PLAY IN PROVIDING ENERGY TO POWER SAR ARCS? (C) WHAT IS THE ROLE OF LARGE SUB-AURORAL ELECTRIC FIELDS IN SAR ARC GENERATION? (D) ARE THERE CONSISTENT SIGNATURES OF EMIC (OR OTHER) WAVES IN REGIONS THAT MAP TO OBSERVED SAR ARCS? METHODOLOGY: IT CONSISTS OF DATA ANALYSIS OF VAP AND THEMIS DATA FOR CASES OF OBSERVED SAR ARCS IDENTIFIED IN ASI DATA SUPPLEMENTED BY RADAR F-REGION AND DMSP TOPSIDE DATA AND BY NUMERICAL SIMULATIONS. WE WILL CLASSIFY THE OBSERVED SAR ARCS IN TERMS OF GEOMAGNETIC CONDITIONS AND STORM PHASE. DATA FROM EIGHT ASIS AT SUB-AURORAL LATITUDES (L~ 3) WITH BROAD LONGITUDINAL DISTRIBUTION WILL BE ANALYZED. WE WILL THEN SEARCH THE COMBINED DATA FROM VAP HOPE RBSPICE EMFISIS AND EFW INSTRUMENTS. WE WILL CHARACTERIZE DC ELECTRIC FIELDS RING CURRENT PARTICLE FLUXES AND ANISOTROPY AND LOCATION OF THE PLASMAPAUSE. ON THEMIS ION AND ELECTRON PARTICLE DATA FROM ESA AND SST INSTRUMENTS AND DENSITY DATA FROM THE SPACECRAFT POTENTIAL WILL BE USED. MILLSTONE HILL RADAR DATA (WHEN AVAILABLE) WILL PROVIDE F-REGION PLASMA DENSITY AND TEMPERATURE HEIGHT PROFILES. WE WILL USE EVENT SIMULATIONS WITH THE SAMI3-RCM FIRST-PRINCIPLES MODEL OF THE RING CURRENT AND IONOSPHERE. CONSTRAINED BY DATA SIMULATIONS WILL BE USED TO COMPUTE SIGNATURES OF RING CURRENT ENERGY LOSSES AND IONOSPHERIC ELECTRON HEATING RATES. OUR COMPARISON WITH RESULTS OF DATA ANALYSIS WILL ALLOWS US TO VALIDATE THEORETICAL PREDICTIONS OR FIND SYSTEMATIC DISCREPANCIES. WORK PLAN: THE PROPOSED WORK INCLUDES: 1) IDENTIFICATION OF STORM PERIODS AND AVAILABLE IN SITU AND GROUND-BASED DATA; 2) COMPUTATION OF FOOTPRINTS OF VAP AND THEMIS TO IDENTIFY OVERFLIGHTS IN BOTH HEMISPHERES THAT MAP INTO THE IONOSPHERE NEAR L=3; 3) ANALYSIS OF THE DATA; 4) NUMERICAL SIMULATIONS TO OBTAIN KEY OUTPUTS; AND 5) CALCULATION OF BRIGHTNESS LEVELS OF RED-LINE EMISSIONS IN REGIONS OF SAR ARCS DUE TO COULOMB COLLISIONS AND SAPS ELECTRIC FIELDS. RELEVANCE: THE PROPOSED WORK IS RELEVANT TO ONE OF THE FOUR SCIENCE GOALS FROM THE DECADAL SURVEY AS IT ADDRESS THE DYNAMICS AND COUPLING OF EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE. IT ALSO ADDRESSES ONE OF THE SCIENCE OBJECTIVES OF VAP BY CONTRIBUTING TO THE UNDERSTANDING OF HOW AND WHY THE RING CURRENT VARIES DURING STORMS.