A THREE-YEAR RESEARCH PROGRAM IS PROPOSED TO STUDY THE ONSET AND EVOLUTION OF EQUATORIAL PLASMA BUBBLES THAT DEVELOP IN THE POST-MIDNIGHT EQUATORIAL IONOSPHERE. THE DEVELOPMENT OF EQUATORIAL IRREGULARITIES IS KNOWN AS EQUATORIAL SPREAD F (ESF) AND TYPICALLY OCCURS AFTER SUNSET. HOWEVER IT HAS BEEN FOUND THAT QUIET-TIME ESF OCCURS IN THE POST-MIDNIGHT SECTOR DURING LOW SOLAR FLUX CONDITIONS. THE OCCURRENCE OF POST-MIDNIGHT ESF WAS EVEN MORE NOTICEABLE DURING THE RECENT EXTREME SOLAR MINIMUM OF 2008/2009. THE PRIMARY OBJECTIVE OF THIS RESEARCH PROGRAM IS TO ANSWER THE QUESTION: WHY DOES ESF DEVELOP IN THE POST-MIDNIGHT SECTOR DURING SOLAR MINIMUM CONDITIONS RATHER THAN IN THE POST-SUNSET SECTOR? WE WILL USE A COMPREHENSIVE DATA/MODELING METHODOLOGY TO ADDRESS THIS OVERARCHING SCIENCE QUESTION. SPECIFICALLY WE WILL USE DATA FROM THE NASA CINDI INSTRUMENT ABOARD THE C/NOFS SATELLITE AND THE NRL IONOSPHERE MODEL SAMI3 TO INVESTIGATE THE CAUSE(S) OF POST-MIDNIGHT F REGION PLASMA IRREGULARITIES. THE CINDI OBSERVATIONS WILL ALSO BE COMPLEMENTED BY GROUND-BASED RADAR MEASUREMENTS. THE C/NOFS SATELLITE MISSION OBTAINED IN SITU IONOSPHERE DATA FROM 2008 TO 2015 WHICH INCLUDES THE EXTREME SOLAR MINIMUM PERIOD 2008 - 2010. THE NASA CINDI INSTRUMENT PROVIDES DATA FOR THE ION VELOCITY VECTOR TEMPERATURE AND COMPOSITION. THESE DATA WILL BE ANALYZED DURING THE MISSION LIFETIME AND WILL PROVIDE INSIGHT INTO THE PHYSICAL DIFFERENCES OF THE IONOSPHERE/THERMOSPHERE SYSTEM FOR SOLAR MINIMUM AND MAXIMUM CONDITIONS. IN CONJUNCTION WITH THE DATA ANALYSIS WE WILL USE THE NAVAL RESEARCH LABORATORY (NRL) GLOBAL HIGH-RESOLUTION IONOSPHERIC CODE SAMI3 WHICH PROVIDES A COMPREHENSIVE DESCRIPTION OF IONOSPHERIC DYNAMICS ON BOTH GLOBAL AND REGIONAL SCALES. IN FACT SAMI3 IS THE ONLY CODE THAT CAN MODEL ESF PLASMA BUBBLES WITHIN A GLOBAL 3D IONOSPHERE MODEL. IT IS THIS UNIQUE CAPABILITY OF SAMI3 THAT MAKES IT POSSIBLE TO ATTACK THE IMPORTANT PROBLEM OF POST-MIDNIGHT ESF DURING SOLAR MINIMUM CONDITIONS. THIS INVESTIGATION DIRECTLY RELATES TO THE HELIOPHYSICS RESEARCH BROAD CATEGORY "IONOSPHERE-THERMOSPHERE-MESOSPHERE " AND TO THE SPECIFIC SCIENCE AREA "IONOSPHERE-ATMOPHERE COUPLING." THE PROPOSED RESEARCH EFFORT FOLLOWS RECOMMENDATIONS DESCRIBED IN THE DECADAL SURVEY. IN PARTICULAR ONE OF THE MAJOR SCIENCE GOALS OF THE DECADAL SURVEY IS TO "DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS." LASTLY UNDERSTANDING AND MODELING IONOSPHERIC PLASMA IRREGULARITIES IS IMPORTANT BECAUSE OF THEIR IMPACT ON SPACE WEATHER. THEY CAN CAUSE SCINTILLATION AND LARGE SPATIAL AND TEMPORAL VARIATIONS IN THE IONOSPHERIC DELAY OF RADIO SIGNALS USED BY SPACE-BASED COMMUNICATION AND NAVIGATION SYSTEMS.