GOALS: MAGNETOHYDRODYNAMIC (MHD) FAST MODE WAVES (FMW) CAN LEAD TO ENHANCEMENTS/DEPLETIONS IN THE RELATIVISTIC ELECTRON POPULATION THAT AFFECTS SATELLITES IN GEOSTATIONARY ORBIT. THE REGION OUTSIDE THE PLASMASPHERE IS IMPORTANT FOR UNDERSTANDING FMW DYNAMICS; WAVES ORIGINATING IN THE SOLAR WIND ION FORESHOCK MAGNETOSHEATH OR OUTER MAGNETOSPHERE MUST PASS THROUGH THIS REGION BEFORE COUPLING TO INNER MAGNETOSPHERE WAVES OR INTERACTING WITH ENERGETIC PARTICLES DEEP IN THE RADIATION BELTS. PREVIOUS MODELING STUDIES MAKE TWO KEY PREDICTIONS: (1) LOW FREQUENCY FMW MOST IMPORTANT FOR RADIATION BELT INTERACTIONS OFTEN HAVE PROPAGATION CUTOFFS OUTSIDE THE PLASMASPHERE (2) FMW HAVE SIGNIFICANTLY SMALLER AMPLITUDES THAN OTHER ULF WAVE MODES. BOTH (1) AND (2) ARE CENTRAL TO OUR UNDERSTANDING OF THE ROLE OF FMW IN RADIATION BELT INTERACTIONS RELATIVE TO OTHER ULF WAVE MODES. HOWEVER THERE ARE FEW OBSERVATIONAL CONSTRAINTS TO TEST THESE PREDICTIONS; NEARLY ALL PREVIOUS STATISTICAL STUDIES OF ULF WAVE PROPERTIES LACKED IN SITU PLASMA MOMENT OBSERVATIONS A CRITICAL LINE OF EVIDENCE OFTEN NEEDED TO DISTINGUISH FMW FROM OTHER ULF WAVE MODES IN THE WARM PLASMA OUTSIDE THE PLASMASPHERE. THIS PROPOSAL IS FOCUSED ON A SINGLE OBJECTIVE DETERMINE THE PROPERTIES OF MAGNETOSPHERIC MHD FMW OUTSIDE THE PLASMASPHERE DURING DIFFERENT DRIVING CONDITIONS AIMED AT ANSWERING TWO SCIENCE QUESTIONS: HOW IS MAGNETOSPHERIC FMW ENERGY DISTRIBUTED OUTSIDE THE PLASMASPHERE AS A FUNCTION OF FREQUENCY AND DRIVING CONDITION? HOW LARGE ARE TYPICAL FMW AMPLITUDES COMPARED TO OTHER ULF WAVE MODES? THE PROPOSED STUDY WILL PROVIDE NEW OBSERVATIONS THAT BETTER CONSTRAIN THE ROLE OF FMW IN RADIATION BELT INTERACTIONS; FOR EXAMPLE THEY CAN BE USED TO DETERMINE WHETHER SOLAR WIND DRIVEN FMW PENETRATE DEEP ENOUGH INTO THE MAGNETOSPHERE TO AFFECT RADIATION BELT DYNAMICS DIRECTLY OR PLAY MORE INDIRECT ROLES BY RESONANTLY COUPLING TO STANDING ALFV N WAVES THAT IN TURN INTERACT WITH RADIATION BELT PARTICLES. MISSION DATA: OUR PRIMARY DATA FOR THESE TASKS ARE PLASMA MOMENT AND MAGNETIC/ELECTRIC FIELD OBSERVATIONS FROM NASA S TIME HISTORY OF EVENTS AND MACROSCALE INTERACTIONS DURING SUBSTORMS (THEMIS) MISSION; WE WILL USE THESE TO UNAMBIGUOUSLY IDENTIFY FMW AND RECORD THEIR AMPLITUDES. THE THEMIS SATELLITES ARE IDEAL FOR THIS STUDY AS THEY ROUTINELY PROVIDE ALL NECESSARY MEASUREMENTS WITH ROUGHLY A DECADE OF OBSERVATIONS NEAR THE MAGNETIC EQUATORIAL PLANE (WHERE FMW ENERGY IS CONCENTRATED) AND OUTSIDE THE PLASMASPHERE. WE WILL ALSO USE DATA FROM NASA S ACE AND WIND SATELLITES VIA THE OMNIWEB INTERFACE TO MONITOR SOLAR WIND CONDITIONS. TIME PERMITTING WE WILL EXAMINE DATA FROM VAN ALLEN PROBES AND MMS THOUGH THESE DATA ARE NOT REQUIRED TO ADDRESS OUR SCIENCE QUESTIONS. DATA ANALYSIS/METHODOLOGY: WE SHALL IDENTIFY FMW AS PERIODS OF WAVE ACTIVITY WITH MAGNETIC AND THERMAL PRESSURE PERTURBATIONS IN PHASE; THIS WILL REMOVE MIRROR MODE AND COMPRESSIONAL ALFVEN WAVES (POLOIDAL MODES) FROM OUR ANALYSIS. THE FMW OCCURRENCE RATE AND OTHER PROPERTIES WILL THEN BE ORDERED ACCORDING TO SPATIAL POSITION FREQUENCY AND UPSTREAM CONDITIONS OBTAINED FROM OMNIWEB. ALL STEPS IN THE METHODOLOGY HAVE BEEN TESTED AND VETTED IN PREVIOUS WORK BY THE PI AND OTHER RESEARCHERS. RELEVANCE: OUR SCIENCE OBJECTIVE ADDRESSES THE DECADAL SURVEY GOAL DETERMINE THE DYNAMICS AND COUPLING OF THE EARTHS MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS. IT IS ALSO RELEVANT TO THE THEMIS MISSION S SECONDARY OBJECTIVE BY DETERMINING THE EXTENT OF THE WAVE FIELDS THAT ARE PROPOSED TO ACCELERATE THE PARTICLES (THEMIS BERKELEY WEBSITE). FINALLY THE PROPOSED OBJECTIVE IS RELEVANT TO THE NASA GI MAGNETOSPHERE SUBDISCIPLINE AND SOLAR WIND MAGNETOSPHERE COUPLING SCIENCE AREA.