SCIENCE GOALS AND OBJECTIVES: IN RECENT YEARS SMALL SCALE AZIMUTHAL STRUCTURING IN OPTICAL SIGNATURES (KNOWN AS AZIMUTHAL AURORAL FORMS OR AURORAL BEADS - E.G. MOTOBA ET AL. 2012) HAVE BEEN OBSERVED AND ARE ASSOCIATED WITH LOW FREQUENCY PC1/2 WAVE ACTIVITY. WHILE THE CHARACTERISTIC FREQUENCY KINETIC-SCALE STRUCTURING AND ASSOCIATED ELECTRON ENERGIZATION HAVE BEEN ATTRIBUTED TO THE ONSET OF A KINETIC BALLOONING INSTABILITY THERE HAS BEEN LIMITED RIGOROUS COMPARISON BETWEEN THE OBSERVATIONS AND THEORETICAL MODELS. THE AIM OF THIS PROPOSAL IS TO UNDERSTAND THE WAVE AND ENERGIZED ELECTRON SIGNATURES ASSOCIATED WITH THE BALLOONING INSTABILITY IN THE NEAR-EARTH PLASMA SHEET BY COMPARING IMAGE THEMIS (SPACECRAFT AND ASI) CLUSTER FAST AND DMSP OBSERVATIONS OF INSTANCES OF AURORAL BEADS WITH SIMULATIONS OF THE HYBRID GYROFLUID-KINETIC-ELECTRON (GKE) MODEL. IN PARTICULAR WE WILL ADDRESS THE FOLLOWING SCIENCE QUESTIONS: 1) WHAT ARE THE OBSERVED WAVE AND ENERGIZED ELECTRON SIGNATURES ASSOCIATED WITH AURORAL BEADS EVIDENT AT SUBSTORM ONSET? 2) HOW WELL DOES THE KINETIC BALLOONING INSTABILITY ACCOUNT FOR THESE OBSERVED WAVE AND ELECTRON SIGNATURES? AND (3) HOW DO THE CHARACTERISTICS OF THE ENERGIZATION VARY WITH AZIMUTHAL MODE NUMBER? METHODOLOGY: TO ANSWER THESE FUNDAMENTAL SCIENCE QUESTIONS WE WILL CONDUCT SIMULATIONS USING THE GYROFLUID-KINETIC ELECTRON (GKE) MODEL (DAMIANO ET AL. 2015) CONSTRAINED BY AND COMPARED WITH CLUSTER THEMIS IMAGE FAST AND DMSP OBSERVATIONS. THE MODEL IS CODED IN CURVILINEAR COORDINATES AND INCORPORATES BOTH COMPRESSIONAL AND ALFV N WAVE PHYSICS INCLUDING THE RELEVANT ELECTRON DYNAMICS THAT DESCRIBE THE INERTIAL AND KINETIC ALFV N WAVE LIMITS (WHERE PARALLEL ELECTRIC FIELDS CAN BE SUPPORTED) ALONG WITH MIRROR FORCE TRAPPING OF ELECTRONS AND FINITE ION-GYRORADIUS EFFECTS. THE MODEL HAS A PROVEN RECORD FOR INVESTIGATING BOTH MONOENERGETIC (E.G. DAMIANO ET AL. 2007 DAMIANO AND WRIGHT 2008; DAMIANO AND JOHNSON 2012 2013) AND BROADBAND (E.G. DAMIANO ET AL. 2015 2016) ELECTRON ENERGIZATION BY ALFV N WAVES IN THE TERRESTRIAL MAGNETOSPHERE. IN THE EXECUTION OF THE WORK PLAN GROUND BASED THEMIS-ASI (ALL SKY IMAGER) DATA WILL BE USED IN CONJUNCTION WITH CLUSTER THEMIS IMAGE FAST AND DMSP SATELLITE OBSERVATIONS TO IDENTIFY AND CLASSIFY INSTANCES OF THE OCCURRENCE OF AURORAL BEADS AND THE ASSOCIATED WAVE AND PARTICLE SIGNATURES. THIS USE OF THESE MULTIPLE SPACECRAFT WILL FACILITATE COMPREHENSIVE DATA COVERAGE ALL ALONG THE FIELD LINE FROM NEAR (OR BELOW) THE LOW ALTITUDE AURORAL ACCELERATION REGION TO THE TAIL PLASMA SHEET. THE CHARACTERISTICS OF THE SATELLITE OBSERVATIONS WILL THEN BE COMPARED WITH GKE SIMULATIONS OF BALLOONING MODES TO ASCERTAIN HOW WELL THE SIMULATED WAVE AND ELECTRON SIGNATURES COMPARE WITH THE OBSERVATIONS. RELEVANCE: THE OBJECTIVES FOR THE PROPOSAL ARE RELEVANT TO THE HELIOPHYSICS DECADAL SURVEY GOAL (2) DETERMINE THE DYNAMICS AND COUPLING OF THE EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS AND GOAL (4) DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE. THE WORK WILL IN-TURN ADVANCE HSR SCIENCE AREA (10) MAGNETOSPHERE-IONOSPHERE COUPLING/MAGNETOTAIL. ALSO THE PROPOSED WORK WILL ANALYZE DATA FROM THE NASA THEMIS IMAGE FAST AND CLUSTER MISSIONS THAT ARE PUBLICLY AVAILABLE FROM THE NASA GSFC SPACE PHYSICS DATA FACILITY WEBSITE HTTP://CDAWEB.GSFC.NASA.GOV). CLUSTER OBSERVATIONS NOT AVAILABLE IN THE SPDA CAN ALSO BE ACCESSED AT HTTPS:// WWW.COSMOS.ESA.INT/WEB/CSA.