DUSK-PREMIDNIGHT PLASMA CONVECTION IN THE SUBAURORAL IONOSPHERE IS OFTEN ENHANCED AT NARROW LATITUDES (SAPS). THE LATITUDINAL EXTENT OF THE FLOWS CAN OCCASIONALLY BECOME A DEGREE OR LESS WITH THE PEAK SPEED EXCEEDING A FEW KM/S. THOSE ARE CALLED SUBAURORAL ION DRIFTS (SAID) AS A SUBSET OF SAPS. SAPS/SAID HAVE BEEN RECOGNIZED AS A FUNDAMENTAL COMPONENT OF THE CONVECTION ELECTRIC FIELD IN THE INNER MAGNETOSPHERE AND THUS ARE KEY FEATURES IN INNER MAGNETOSPHERE-IONOSPHERE COUPLING. THE OVERARCHING GOAL OF THIS PROPOSED STUDY IS TO DETERMINE OCCURRENCE CONDITIONS AND PROPERTIES OF SAID WITH A PARTICULAR EMPHASIS ON WHAT PROCESSES PREFERABLY DRIVE SAID RATHER THAN SAPS (WITHOUT SAID). THREE SPECIFIC SCIENCE QUESTIONS ARE PROPOSED: (1) HOW DO SAID RELATE TO INJECTION BOUNDARIES AND PLASMAPAUSE? (2) WHAT ARE SOLAR WIND AND GEOMAGNETIC CONDITIONS THAT FAVOR SAID? (3) HOW DO SAID OCCURRENCE RELATE TO MAGNETOTAIL CONDITIONS? THIS INVESTIGATION IS TIMELY BECAUSE THE 2ND NIGHTSIDE SEASONS BY RBSP HAS BEEN COMPLETED AND THEMIS HAS ACHIEVED 10 YEARS OF MEASUREMENTS GIVING A SOLID DATASET TO ADDRESS THE PROPOSED QUESTIONS AND BECAUSE COMMUNITY S ATTENTION TO INNER MAGNETOSPHERE PHYSICS IS FURTHER INCREASING DUE TO THE RECENT LAUNCH OF THE ERG MISSION. THE PROPOSAL USES A UNIQUE APPROACH (SEE SECTION 2 AND 4) TO HIGHLIGHT 2-D TRANSPORT PROCESSES IN COMBINATION WITH THE SATELLITES TO IDENTIFY FUNDAMENTAL DIFFERENCES IN THE MODES OF INNER MAGNETOSPHERE CONVECTION. RELEVANCE TO THE GI PROGRAM: THIS PROPOSED STUDY AIMS TO UNDERSTAND FUNDAMENTAL FEATURES OF THE ELECTRIC FIELD IN THE INNER MAGNETOSPHERE AND THUS THIS STUDY WILL ADDRESS DECADAL SURVEY GOALS #2 DETERMINE THE DYNAMICS OF EARTH S MAGNETOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS AND #4 DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THIS STUDY WILL PRIMARILY USE CURRENT NASA MISSION DATA FROM THEMIS VAN ALLEN PROBES GEOTAIL ACE AND WIND (OMNI) PARTICULARLY FOR ADDRESSING THE FIRST AND THIRD SCIENCE QUESTIONS. NON- NASA DATASET WILL ALSO BE USED AS SECONDARY DATASETS TO ASSIST CLOSING THE PROPOSED SCIENCE. SPECIFIC SCIENCE QUESTIONS DATA METHOD AND WORK PLAN: (1) HOW DO SAID RELATE TO INJECTION BOUNDARIES AND PLASMAPAUSE? BY TAKING ADVANTAGE OF IN-SITU MEASUREMENTS WE WILL DETERMINE HOW THE EARTHWARD AND TAILWARD BOUNDARIES OF SAID RELATE TO TRAPPED PLASMA POPULATION NAMELY ELECTRON AND ION INJECTION BOUNDARIES AND PLASMAPAUSE MEASURED BY THEMIS AND VAN ALLEN PROBES. THOSE WILL BE COMPARED TO SAPS EVENTS WITHOUT SAID TO EXAMINE HOW DIFFERENTLY PLASMA BOUNDARIES RELATE TO SAID ELECTRIC FIELD. (2) WHAT ARE SOLAR WIND AND GEOMAGNETIC CONDITIONS THAT FAVOR SAID? WHILE BOTH SAPS AND SAID PREFERENTIALLY OCCUR DURING GEOMAGNETICALLY ACTIVE TIMES THEIR TIMINGS HAVE NOTABLE DIFFERENCES. SAPS INITIATE AT OR SOON AFTER SUBSTORM ONSET WHILE SAID TEND TO OCCUR SUBSTANTIALLY AFTER SUBSTORM ONSET (>30 MIN). USING SATELLITE-GROUND COORDINATION EVENTS WE WILL DETERMINE IN WHAT GEOMAGNETIC CONDITIONS SAID TEND TO OCCUR. PARTICULARLY WE WILL DETERMINE WHAT REGULATES INITIATION AND TERMINATION OF SAID. WE WILL IDENTIFY STORM AND SUBSTORM PHASES IN GEOMAGNETIC INDICES AND INJECTIONS IN IMAGER DATA. (3) HOW DO SAID OCCURRENCE RELATE TO MAGNETOTAIL CONDITIONS? WE WILL DETERMINE HOW DIFFERENT MAGNETOTAIL CONDITIONS ARE DURING SAID EVENTS AS COMPARED TO SAPS WITHOUT SAID. USING THEMIS AND GEOTAIL WE WILL CHARACTERIZE LOCATION AND STRENGTH OF PARTICLE INJECTIONS PLASMA SHEET DENSITY AND TEMPERATURE WHICH DETERMINE HOW DEEPLY PARTICLES ARE INJECTED INTO THE INNER MAGNETOSPHERE. SUPERDARN IN THE PREMIDNIGHT SECTOR WILL BE USED TO DETECT SAID AND ITS ENHANCEMENTS ASSOCIATED WITH INJECTIONS.