SUBAURORAL POLARIZATION STREAMS (SAPS) ARE A LATITUDINALLY NARROW BAND OF HIGH-SPEED PLASMA DRIFTS OCCURRING MOSTLY IN THE AFTERNOON TO MIDNIGHT SECTOR. THEY ARE LOCATED IN A REGION THAT IS JUST OUTSIDE OF THE AURORAL OVAL OF ELECTRON PRECIPITATION WHERE THE DOWNWARD REGION-2 CURRENTS FROM THE INNER MAGNETOSPHERE FLOW THROUGH THE LOW IONOSPHERIC CONDUCTIVITY REGION OF MIDDLE LATITUDE PLASMA DENSITY TROUGH AND ARE CLOSED BY THE UPWARD REGION-1 CURRENTS TO THE MAGNETOSPHERE IN THE AURORAL OVAL. THIS REGION IS THUS THE DYNAMIC INTERFACE OF DIFFERENT REGIMES OF THE COUPLED MAGNETOSPHERE IONOSPHERE THERMOSPHERE (M-I-T) SYSTEM. COMPLEX PHYSICAL PROCESSES OF DIFFERENT TEMPORAL AND SPATIAL SCALES OCCUR IN THIS REGION. A FULL DESCRIPTION OF THE FUNDAMENTAL PHYSICAL PROCESSES THAT GOVERN THE OCCURRENCE CHARACTERISTICS VARIATIONS AND EFFECTS OF SAPS IS STILL ELUSIVE AND CHALLENGING BECAUSE IT REQUIRES A SYSTEMATIC APPROACH INVOLVING HIGH-RESOLUTION FIRST PRINCIPLES SIMULATIONS AND COMPREHENSIVE OBSERVATIONS OF THE ENTIRE M-I-T SYSTEM. THESE MODELING AND OBSERVATIONAL CAPABILITIES HAVE NOT BEEN AVAILABLE UNTIL RECENTLY. HERE WE PROPOSE TO EXPLORE AND UNDERSTAND THESE PHYSICAL PROCESSES THEIR CHANGES WITH SOLAR WIND AND GEOPHYSICAL CONDITIONS AND THEIR EFFECTS ON THE M-I-T SYSTEM THROUGH NUMERICAL SIMULATIONS AND MODEL-DATA COMPARISONS. THIS GOAL WILL BE ACHIEVED BY ADDRESSING THE FOLLOWING SCIENTIFIC QUESTIONS: 1) HOW DO SAPS CHANGE WITH SOLAR WIND AND GEOPHYSICAL CONDITIONS? 2) WHAT ARE THE EFFECTS OF SAPS ON THE GLOBAL I-T SYSTEM? 3) WHAT ARE THE FEEDBACK EFFECTS OF THE I-T CHANGES DURING SAPS EVENTS ON M-I COUPLING AND THE MAGNETOSPHERE?