DURING GEOMAGNETIC STORMS A LARGE VOLUME OF IONS IS TRANSPORTED FROM THE MAGNETOTAIL DEEP INTO THE INNER MAGNETOSPHERE LEADING TO ION ACCELERATION TO THE ENERGIES OF TENS TO HUNDREDS KEV. ENERGIZED IONS BECOME THE DOMINANT SOURCE OF PLASMA PRESSURE IN THE INNER MAGNETOSPHERE. ION ACCELERATION AND TRANSPORT FROM THE TAIL INTO THE INNER MAGNETOSPHERE CAN OCCUR AT DIFFERENT SPATIAL AND TEMPORAL SCALES RANGING FROM GLOBAL QUASI-STEADY CONVECTION TO LOCALIZED IMPULSIVE INJECTION EVENTS. THE OVERARCHING GOAL OF THE PROPOSED RESEARCH IS TO ADVANCE THE PHYSICAL UNDERSTANDING OF THESE MULTI-SCALE PROCESSES. SPECIFICALLY WE WILL ADDRESS THE FOLLOWING SCIENCE QUESTIONS: SQ1 INJECTION PROPERTIES. HOW DEEP INTO THE INNER MAGNETOSPHERE CAN LOCALIZED ION INJECTIONS PENETRATE? WHAT ARE THEIR PROPERTIES (SPATIAL EXTENT MAXIMUM ENERGY ION COMPOSITION)? HOW DO THE INJECTION PROPERTIES DEPEND ON GEOMAGNETIC ACTIVITY AS MEASURED BY GLOBAL INDICES (DST AL) AND THE LEVEL OF SOLAR WIND DRIVING? SQ2 ACCELERATION MECHANISMS. WHAT ARE THE MAGNETOTAIL SOURCE POPULATIONS (I.E. LOCATION ENERGY PITCH-ANGLE DISTRIBUTION) OF ENERGETIC IONS IN THE INNER MAGNETOSPHERE? WHAT ARE THE RELATIVE ROLES OF THE ADIABATIC AND NON-ADIABATIC MECHANISMS IN THE ACCELERATION OF DIFFERENT ION SPECIES (H HE O)? SQ3 RELATIVE CONTRIBUTIONS. WHAT ARE THE RELATIVE CONTRIBUTIONS OF GLOBAL MAGNETOSPHERIC CONVECTION AND LOCALIZED INJECTIONS IN THE BUILDUP OF STORM-TIME RING CURRENT? THE PROPOSED INVESTIGATION IS BUILT ON THE SYNERGY BETWEEN DATA ANALYSIS OF ENERGETIC ION ACCELERATION AND TRANSPORT AND STATE-OF-THE-ART MODELING TECHNIQUES. TO QUANTIFY INJECTION PROPERTIES WE WILL USE ENERGETIC ION MEASUREMENTS WITH THE COMPOSITION (H: 10-600 KEV HE: 70-1 MEV O: 40 KEV - 1 MEV) FROM THE RBSPICE INSTRUMENT OF THE TWIN SPACECRAFT VAN ALLEN PROBES MISSION. USING A LARGE DATABASE (>100) OF INJECTIONS ON RBSPICE WE WILL CATALOGUE THE FOLLOWING PROPERTIES: (1) THE MLT AND L OF THE INJECTION SITE; (2) ION COMPOSITION; (3) THE MAXIMUM ENERGY OF EACH ION SPECIES; (4) THE PARTIAL CONTRIBUTION TO PLASMA PRESSURE; (4) THE GEOMAGNETIC CONDITIONS PARAMETERIZED BY THE STORM (DST INDEX) AND THE SUBSTORM ACTIVITY (AL INDEX); (5) THE LEVEL OF THE SOLAR WIND DRIVING MEASURED BY THE SOLAR WIND CONVECTION ELECTRIC FIELD (VBS). A GLOBAL MHD-RING CURRENT MODEL (LFM-RCM) WILL BE USED FOR SIMULATING THE ELECTRIC AND MAGNETIC FIELDS ASSOCIATED WITH GLOBAL MAGNETOSPHERIC CONVECTION AND SMALL-SCALE LOCALIZED INJECTIONS. A THREE-DIMENSIONAL TEST-PARTICLE APPROACH IN THE MHD-SIMULATED ELECTROMAGNETIC FIELDS WILL BE USED FOR THE DETAILED ANALYSIS OF ION ACCELERATION. FIRST WE WILL RUN A SERIES OF BACKWARD TEST-PARTICLE SIMULATIONS TO IDENTIFY THE LOCATION AND PROPERTIES OF ION SOURCE POPULATIONS IN THE MAGNETOTAIL. THEN TO IDENTIFY THE RELATIVE ROLES OF ADIABATIC AND NON-ADIABATIC MECHANISMS IN THE ACCELERATION OF DIFFERENT ION SPECIES WE WILL CONDUCT FORWARD TEST-PARTICLE SIMULATIONS USING THE FULL LORENTZ FORMULATION AS WELL AS THE GUIDING-CENTER APPROXIMATION AND COMPARE THEIR RESULTS WITH ION SPECTRA OBSERVED BY RBSPICE. FINALLY WE WILL DETERMINE THE RELATIVE CONTRIBUTIONS OF GLOBAL CONVECTION AND LOCALIZED INJECTIONS TO THE BUILDUP OF RING CURRENT PRESSURE BY CONDUCTING FORWARD TEST-PARTICLE SIMULATIONS IN (A) TIME-AVERAGED CONVECTION FIELDS AND (B) IN THE UNATTENUATED FIELDS WHICH ACCOUNT FOR BOTH GLOBAL CONVECTION AND LOCALIZED TRANSIENT EVENTS. SIMULATION RESULTS WILL BE USED TO COMPUTE TOTAL ION PRESSURE IN INNER MAGNETOSPHERE. THIS WILL PROVIDE CLOSURE OVER THE GOALS OF THE PROPOSED RESEARCH. THE GOAL OF THIS PROJECT IS DIRECTLY RELEVANT TO GOALS 2 AND 4 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 DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE .