US PARTICIPATION IN THE THOR MISSION PHASE ATHIS PROPOSAL SEEKS FUNDING TO PARTICIPATE IN THE ESA PHASE A STUDY FOR THE TURBULENCE HEATING OBSERVER MISSION (THOR). WE PROPOSE TO CONTRIBUTE TO AN ION MASS SPECTROMETER (IMS) A TURBULENCE ELECTRON ANALYZER (TEA) FOR ELECTRONS AND AN ELECTRIC FIELD INSTRUMENT (EFI) TO THE THOR MISSION. THIS MISSION IS DESIGNED TO ANSWER THE SCIENCE QUESTIONS:1) HOW IS PLASMA HEATED AND PARTICLES ACCELERATED?2) HOW IS THE DISSIPATED ENERGY PARTITIONED?3) HOW DOES DISSIPATION OPERATE IN DIFFERENT REGIMES OF TURBULENCE?UNDERSTANDING THE PHYSICAL PROCESSES OF PARTICLE ACCELERATION HEATING AND TURBULENCE IS KEY TO UNDERSTANDING PLASMA PROCESSES IN THE MAGNETOSPHERE THE SOLAR WIND PLANETARY ENVIRONMENT AND EVEN ASTROPHYSICAL SETTINGS. THIS MISSION FOCUSES ON MAKING MEASUREMENTS AT HIGH TIME RESOLUTION ON THE ION AS WELL AS THE ELECTRON SCALE SO THAT THE PHYSICS IN BOTH REGIMES CAN BE ADDRESSED. THORS PRIMARY SCIENCE OBJECTIVES RELATE DIRECTLY TO THREE OF THE KEY SCIENCE GOALS RECOMMENDED BY THE 2013 NRC DECADAL SURVEY IN SPACE AND SOLAR PHYSICS:GOAL 1. DETERMINE THE ORIGINS OF THE SUNS ACTIVITY AND PREDICT THE VARIATIONS IN THE SPACE ENVIRONMENT.GOAL 2. DETERMINE THE DYNAMICS AND COUPLING OF EARTHS MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS.GOAL 4. DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE.THIS MISSION DIRECTLY ADDRESSES FUNDAMENTAL PROCESSES AND THE PROPOSED US CONTRIBUTION IS CRITICAL TO THE MISSION GOALS AND SUCCESS.