THE PRIMARY GOAL OF THIS PROPOSAL IS TO ELUCIDATE THE CAUSAL RELATIONSHIP BETWEEN THE HIGH-LATITUDE ENERGY INPUT AND THE FORMATION OF THERMOSPHERIC NEUTRAL MASS DENSITY ANOMALY THROUGH DETAILED MODEL-DATA INTERCOMPARISON. MORE SPECIFICALLY WE WILL ADDRESS THE FOLLOWING OUTSTANDING SCIENTIFIC QUESTIONS: (1) WHAT ARE THE SPATIAL AND TEMPORAL DISTRIBUTIONS OF HIGH-LATITUDE ENERGY INPUT IN TERMS OF JOULE HEATING AND AURORAL PRECIPITATION FOR DIFFERENT SOLAR WIND AND GEOMAGNETIC CONDITIONS? WHAT IS THE PARTITION OF ENERGY INPUT OVER THE POLAR CAP COMPARED TO THAT IN THE AURORAL ZONE? (2) HOW DOES THE THERMOSPHERE RESPOND TO HIGH-LATITUDE ENERGY INPUT? WHAT IS THE RELATIVE IMPORTANCE OF THE DIFFERENT PHYSICAL PROCESSES THAT DRIVE THERMOSPHERIC NEUTRAL DENSITY DISTRIBUTIONS IN THE POLAR CAP AS WELL AS AT MIDDLE AND LOW LATITUDES? (3) WHAT IS THE RELATIVE IMPORTANCE OF JOULE HEATING VERSUS AURORAL PRECIPITATION ON THERMOSPHERIC DENSITY ANOMALY? WHAT FRACTION OF JOULE AND AURORAL ENERGY INPUT IS DEPOSITED IN THE UPPER THERMOSPHERE WHERE ITS INFLUENCE ON DENSITY IS GREATER? THESE QUESTIONS ARE IMPORTANT NOT ONLY FOR UNDERSTANDING THE PHYSICAL PROCESSES GOVERNING THE GLOBAL THERMOSPHERE BUT ALSO FOR PREDICTING THE NEAR-EARTH SPACE WEATHER AS THERMOSPHERIC DENSITY PERTURBATIONS POSSESS SERIOUS HAZARDS TO SATELLITE OPERATIONS. THIS INVESTIGATION WILL MAKE EXTENSIVE USE OF DATA FROM BOTH CURRENT AND PAST NASA MISSIONS INCLUDING TIMED C/NOFS AND IMAGE LEVERAGED BY OTHER SPACE AND GROUND BASED OBSERVATIONS IN ORDER TO OBTAIN THE MOST REALISTIC SPECIFICATION OF HIGH-LATITUDE ENERGY INPUT UNDER DIFFERENT SOLAR WIND AND GEOMAGNETIC CONDITIONS BY APPLYING THE ASSIMILATIVE MAPPING OF IONOSPHERIC ELECTRODYNAMICS (AMIE) PROCEDURE. WE WILL USE THE THERMOSPHERE-IONOSPHERE-ELECTRODYNAMICS GENERAL CIRCULATION MODEL (TIEGCM) TO DELINEATE THE VARIOUS DYNAMICAL AND CHEMICAL PROCESSES AFFECTING THE THERMOSPHERE. NUMERICAL SIMULATIONS WITH THE TIEGCM WILL BE CARRIED OUT TO DETERMINE THE SPATIAL AND TEMPORAL SCALES OF THERMOSPHERIC DISTURBANCES AND TO QUANTIFY THE RELATIVE IMPORTANCE OF JOULE HEATING AND AURORAL PRECIPITATION ON THE THERMOSPHERE. THE PROPOSAL DIRECTLY ADDRESSES THE 2ND HIGH-LEVEL SCIENCE GOAL OF THE HELIOPHYSICS DECADAL SURVEY: DETERMINE THE DYNAMICS AND COUPLING OF EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS AND IS HIGHLY RELEVANT TO NASA S STRATEGIC GOALS TO EXPLORE THE PHYSICAL PROCESSES IN THE SPACE ENVIRONMENT FROM THE SUN TO THE EARTH AND TO DEVELOP THE KNOWLEDGE AND CAPABILITY TO DETECT AND PREDICT EXTREME CONDITIONS IN SPACE TO PROTECT LIFE AND SOCIETY AS OUTLINED IN THE HELIOPHYSICS SCIENCE AND TECHNOLOGY ROADMAP FOR 2014-2033. OUR PROPOSAL IS FULLY IN LINE WITH THESE HIGH-PRIORITY SCIENCE OBJECTIVES. THE PROPOSED INVESTIGATION WILL ADVANCE OUR UNDERSTANDING OF ENERGETIC COUPLING OF THE IT SYSTEM A CRITICAL STEP TOWARD A MORE RELIABLE SPECIFICATION AND EVENTUAL FORECAST OF THE THERMOSPHERE. AN IMPROVED UNDERSTANDING OF HOW HIGH-LATITUDE ENERGY INPUT AFFECT THE THERMOSPHERE FROM HIGH LATITUDES TO THE MID- AND LOW-LATITUDE REGIONS WILL GREATLY BENEFIT THE UPCOMING MISSIONS (E.G. ICON AND GOLD). KNOWLEDGE GAINED THROUGH THIS INVESTIGATION CONCERNING THE SPATIAL AND TEMPORAL SCALES OF THERMOSPHERIC VARIABILITY WILL ALSO AID THE DESIGN AND OPTIMIZATION OF FUTURE MULTI-SPACECRAFT CONSTELLATION MISSIONS SUCH AS GDC.