ELECTROMAGNETIC ION CYCLOTRON (EMIC) WAVES ARE PERVASIVE PLASMA WAVES THAT CAN SCATTER ENERGETIC PARTICLES AND HEAT COLD PARTICLES. PAST WORK HAS ALSO HINTED AT ASSOCIATIONS BETWEEN PLASMA COMPOSITION AND WAVES OBSERVED AT DIFFERENT MAGNETOSPHERIC LOCATIONS. THE PRIMARY SCIENCE OBJECTIVE OF THIS PROPOSAL IS TO SPECIFICALLY INVESTIGATE THE LOW-ENERGY PLASMA COMPOSITION AND ITS EFFECTS ON EMIC WAVE PROPERTIES USING MAGNETOSPHERIC MULTISCALE'S DISTINCTIVE INSTRUMENTATION AND MULTI-SATELLITE WAVE AND PARTICLE MEASUREMENT CAPABILITIES. WE WILL ANALYZE MMS PARTICLE AND WAVE MEASUREMENTS WHEN EMIC WAVES ARE PRESENT. WE WILL INCLUDE TIMES WHEN FAST PLASMA FLOWS (CONVECTION ULF WAVES IONOSPHERIC OUTFLOWS) ACCELERATE THE USUALLY HIDDEN COLD PLASMA CORE INTO THE ENERGY RANGE MEASURED BY THE PARTICLE INSTRUMENTS. SUCH FLOWS ALONG OR ACROSS THE MAGNETIC FIELD ARE OPPORTUNITIES TO MEASURE THE FULL LOW-ENERGY PLASMA COMPOSITION (FULL DISTRIBUTION FUNCTIONS PER ION SPECIES) AND FURTHER ANALYZE EFFECTS OF MULTIPLE ION SPECIES ON EMIC WAVE PROPERTIES. WE WILL APPLY PUBLIC MMS MISSION DATASETS (THAT ARE AVAILABLE 30 DAYS PRIOR STEP-2 DEADLINE) DURING SINGLE SATELLITE AND MULTI-SATELLITE EMIC WAVE ACTIVITY TOWARDS THIS INVESTIGATION. THIS INCLUDES APPLICATION OF DATA GATHERED TO TESTS OF LINEAR THEORY OF EMIC WAVES FOR VARIOUS MAGNETOSPHERIC LOCATIONS AND ACTIVITY CONDITIONS. MMS DATA FOR APPLICATION TO THIS STUDY APPEAR BELOW. WE WILL USE SPACE PHYSICS ENVIRONMENT DATA ANALYSIS SOFTWARE (SPEDAS) FOR THE ANALYSIS. SIMILAR TOOLS AND METHODOLOGY HAVE BEEN SUCCESSFULLY APPLIED TO STUDIES ON THEMIS AND MMS DATA CITED BELOW. MMS DATASETS BY INSTRUMENT (ACRONYM): FAST PLASMA INSTRUMENT-DUAL ION AND ELECTRON SENSORS (FPI-DIS&DES) HOT PLASMA COMPOSITION ANALYZER (HPCA) ACTIVE SPACECRAFT POTENTIAL CONTROL DEVICE (ASPOC) SPIN-PLANE AND AXIAL DOUBLE PROBES (SDP&ADP) ANALOG AND DIGITAL FLUXGATE MAGNETOMETERS (AFG&DFG I.E. FGM) ENERGETIC ION SPECTROMETER (EIS) ANALYSIS TOOLS&METHODOLOGY: - ANALYSIS OF PARTICLE DISTRIBUTION FUNCTIONS AND COMPOSITION: LEE J. H. AND V. ANGELOPOULOS (2014) ON THE PRESENCE AND PROPERTIES OF COLD IONS NEAR EARTH'S EQUATORIAL MAGNETOSPHERE JGR-SPACE DOI:10.1002/2013JA019305. - EMIC WAVE ANALYSIS AND MODELING: (1) LEE J. H. AND V. ANGELOPOULOS (2014) OBSERVATIONS AND MODELING OF EMIC WAVE PROPERTIES IN THE PRESENCE OF MULTIPLE ION SPECIES AS FUNCTION OF MAGNETIC LOCAL TIME JGR-SPACE DOI:10.1002/2014JA020469; (2) LEE J. H. L. CHEN V. ANGELOPOULOS AND R. M. THORNE (2012) THEMIS OBSERVATIONS AND MODELING OF MULTIPLE ION SPECIES AND EMIC WAVES: IMPLICATIONS FOR A VANISHING HE+ STOP BAND JGR-SPACE DOI:10.1029/2012JA017539. - MULTI-SATELLITE WAVE ANALYSIS: TURNER D. L. J. H. LEE ET AL. (2017) EXAMINING COHERENCY SCALES SUBSTRUCTURE AND PROPAGATION OF WHISTLER-MODE CHORUS ELEMENTS WITH MMS JGR-SPACE DOI:10.1002/2017JA024474. RELEVANCE&BROADER IMPACTS:THE PLASMA COMPOSITION AND WAVE DATA PRODUCTS WE WILL COMPILE ARE TIMELY AND RELEVANT TO NASA MMS. FOR EXAMPLE HIGH CONCENTRATION OF LOW-ENERGY HEAVY IONS MAY INFLUENCE MAGNETIC RECONNECTION OCCURRING AT THE MAGNETOPAUSE OR IN THE MAGNETOTAIL. THE PROJECT IS RELEVANT TO THE HELIOPHYSICS DECADAL SURVEY (HDS) GOAL: "DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS" AND TO THE SCIENCE AREA "MAGNETOSPHERE-IONOSPHERE COUPLING". OUTCOMES WILL HAVE BROADER IMPACTS LIKE PROVIDING CONTEXT FOR PAST AND ONGOING THEMIS MEASUREMENTS. BECAUSE PLASMA COMPOSITION REGULATES THE EFFECTIVENESS OF EMIC WAVES IN SCATTERING ENERGETIC PARTICLES THE OUTCOMES ARE APPLICABLE TO HIGH PRIORITY SCIENCE GOALS OF THE VAN ALLEN PROBES MISSION. THE RELEVANCE OF OUR PROJECT ACROSS SATELLITE MISSIONS HIGHLIGHTS ITS RELEVANCE TO THE BROAD HDS GOALS AND TO NASA.