SCIENCE GOALS AND OBJECTIVES: THE ROLE OF MAGNETIC TOPOLOGY IN SOLAR-WIND ACCELERATION IS A FUNDAMENTAL UNSOLVED PROBLEM IN SOLAR PHYSICS. PSEUDOSTREAMERS DIFFER FROM THE MORE TRADITIONAL HELMET STREAMERS IN THAT THEY SEPARATE OPEN-FIELD LINES OF THE SAME POLARITY RATHER THAN THE OPPOSITE POLARITY. CURRENTLY THERE IS NO CONSENSUS ON THE NATURE OF SOLAR WIND ASSOCIATED WITH PSEUDOSTREAMERS. WE WILL PRODUCE THE DEFINITIVE OBSERVATIONAL SURVEY QUANTIFYING PSEUDOSTREAMER MORPHOLOGIES TOPOLOGIES AND PHYSICAL PARAMETERS AND COMPARE TO HELMET STREAMER PROPERTIES AND SOLAR-WIND MODEL PREDICTIONS. IN PARTICULAR WE WILL ANSWER THE FOLLOWING QUESTIONS: 1) ARE THERE STANDARD MORPHOLOGICAL FEATURES ASSOCIATED WITH PSEUDOSTREAMERS? HOW DO THESE COMPARE TO HELMET STREAMERS? DO THEY DEPEND ON CORONAL LOCATION?; 2) WHAT ARE THE PHYSICAL AND TOPOLOGICAL PROPERTIES OF PSEUDOSTREAMERS AND HOW DO THESE COMPARE TO HELMET STREAMERS?; AND 3) DO THE SAME PHYSICAL PROCESSES THAT HEAT AND ACCELERATE THE SLOW SOLAR WIND IN HELMET STREAMERS OPERATE IN PSEUDOSTREAMERS? MISSION DATA AND MODELING: THIS INVESTIGATION WILL USE DATA FROM CURRENTLY-OPERATING MISSIONS OF THE HELIOPHYSICS SYSTEM OBSERVATORY: SOHO AND SDO; AND FROM GROUND-BASED OBSERVATORIES COMBINED WITH POTENTIAL FIELD SOURCE SURFACE (PFSS) MODELS AND FORWARD MODELING (USING THE SOLARSOFT IDL FORWARD PACKAGE). ALL DATA AND MODELS ARE PUBLICLY AVAILABLE. METHODOLOGY: WE WILL 1) SYSTEMATICALLY STUDY THE CORONAL MORPHOLOGY AND LOCATION OF PSEUDOSTREAMERS FOR SOLAR CYCLES 23 AND 24 (TO DATE) USING DATA FROM SOHO SDO AND GROUND-BASED OBSERVATORIES; 2) MEASURE AND COMPARE PSEUDOSTREAMER AND HELMETSTREAMER PHYSICAL PARAMETERS INCLUDING ELECTRON DENSITY AND TEMPERATURE PROTON AND ION TEMPERATURES OUTFLOW VELOCITIES ELEMENTAL COMPOSITION AND VARIABILITY; 3) PROBE THE MAGNETIC STRUCTURE OF PSEUDOSTREAMERS AND TEST THE VALIDITY OF EXTRAPOLATIONS BY MEASURING STOKES LINEAR POLARIZATION IN OPTICALLY-THIN IR CORONAL EMISSION LINES AND COMPARING TO FORWARD-MODELED LINEAR POLARIZATION AND MAGNETIC EXPANSION FACTORS DETERMINED FROM PFSS EXTRAPOLATIONS; AND 4) CONSTRAIN AND DRIVE THE DEVELOPMENT OF THEORETICAL MODELS OF CORONAL HEATING AND SOLAR WIND ACCELERATION BY COMPARING OUR MEASURED QUANTITIES WITH MODEL PREDICTIONS. RELEVANCE TO NASA: THE PROPOSED INVESTIGATION WILL EXTEND THE FRONTIER OF THE EXISTING KNOWLEDGE OF SOLAR WIND SOURCE REGIONS BY 1) CONNECTING MAGNETIC TOPOLOGY WITH PLASMA PARAMETERS; AND 2) EXPLORING VARIATION OF HEATING AND ACCELERATION PROCESSES DUE TO DIFFERENT MAGNETIC TOPOLOGIES AND GLOBAL DIFFERENCES IN SOLAR ACTIVITY LEVEL. THIS STRONGLY SUPPORTS THE HELIOPHYSICS RESEARCH OBJECTIVE TO UNDERSTAND THE FUNDAMENTAL PHYSICAL PROCESSES OF THE SPACE ENVIRONMENT FROM THE SUN TO THE EARTH TO OTHER PLANETS AND BEYOND TO THE INTERSTELLAR MEDIUM. (STRATEGIC GOAL 3B.1). THE RESEARCH OBJECTIVES ARE IDEALLY SUITED TO ADDRESS THE HELIOPHYSICS DECADAL SURVEY GOALS #1. "DETERMINE THE ORIGINS OF THE SUN'S ACTIVITY AND PREDICT THE VARIATIONS IN THE SPACE ENVIRONMENT" AND #4. "DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE.