THIS WORK WILL USE SATELLITE DATA AND GLOBAL MODELING TO DETERMINE WHETHER THE UPWARD EXTENSION OF THE WINTER POLAR VORTEX TO MESOPAUSE HEIGHTS ACTS TO VERTICALLY COUPLE THE SUN-EARTH SYSTEM. THIS EFFORT IS MOTIVATED BY THE ENERGETIC PARTICLE PRECIPITATION INDIRECT EFFECT (EPP IE) WHEREBY NITROGEN OXIDES (NOX=NO+NO2) PRODUCED BY EPP (EPP-NOX) ARE TRANSPORTED DOWNWARD IN THE ATMOSPHERE AND DESTROY OZONE. WE WILL EMPLOY A NOVEL AND ROBUST METHOD TO IDENTIFY THE HIGH ALTITUDE VORTEX AS A LAGRANGIAN COHERENT STRUCTURE (LCS). LCSS ARE SURFACES OF MAXIMUM SEPARATION IN FLUID SYSTEMS ACTING AS BARRIERS TO MATERIAL TRANSPORT IN NONLINEAR TIME-VARYING FLOWS. IN THIS WORK WE ASK: DO LCSS SPAN THE MESOPAUSE AND ACT TO FOCUS DESCENT OF EPP-NOX WITHIN THEIR INTERIOR? IN THE LAST DECADE IT HAS BECOME WIDELY APPRECIATED THAT THE WINTERTIME POLAR VORTICES PLAY A CENTRAL ROLE IN VERTICALLY COUPLING THE ATMOSPHERE FROM THE GROUND TO GEOSPACE. IN TERMS OF THE EPP IE THE ATMOSPHERIC RESPONSE IS LARGEST WHEN THE VORTEX IN THE MESOSPHERE IS STRONG ; HOWEVER THUS FAR THE CONNECTION HAS BEEN QUALITATIVE. LCSS ARE BARRIERS THAT DEFINE DIFFERENT CHARACTERISTIC REGIONS OF A FLOW; THEY ARE OBJECTIVE AND QUANTIFIABLE AS THE SURFACE OF MAXIMUM FINITE TIME LYAPUNOV EXPONENT. THE IMPLICATIONS OF A RECENT STUDY OF LCSS IN THE THERMOSPHERE ARE TWO-FOLD WITH RESPECT TO NOX: FIRST SINCE THERMOSPHERIC LCSS ARE CORRELATED WITH GEOMAGNETIC ACTIVITY THE LCSS MAY RELATE TO REGIONS OF NO PRODUCTION. SECONDLY IT IS POSSIBLE THAT ONCE THE NOX IS PRODUCED THE LCSS THEN ACT AS A BARRIER IN DETERMINING THE TRANSPORT OF THE NOX THROUGHOUT THE THERMOSPHERE. WE HYPOTHESIZE THAT LCSS SERVE AS BOUNDARIES TO THE WINTER POLAR VORTEX AND THAT THEY VARY WITH ALTITUDE. THIS WORK WILL DETERMINE HOW OFTEN AND TO WHAT EXTENT LCSS EXIST AT MESOPAUSE ALTITUDES AND QUANTIFY THE RELATIONSHIP BETWEEN LCS SIZE STRENGTH AND ZONAL SYMMETRY AND NOX DISTRIBUTIONS. THE OVERARCHING GOAL OF THE PROPOSED WORK IS TO EVALUATE AND DEMONSTRATE THE USE OF LCSS FOR DIAGNOSING VERTICAL TRANSPORT IN THE ATMOSPHERE. IN PARTICULAR WE SEEK TO IDENTIFY LCSS NEAR THE WINTER MESOPAUSE AND QUANTIFY THEIR ROLE IN VERTICAL COUPLING THE ATMOSPHERE VIA EPP WITH DATA ASSIMILATIVE MODELING TO PROVIDE REALISTIC EPP IE FLOWS. THIS WORK RESPONDS TO THE MOST RECENT HELIOPHYSICS DECADAL SURVEY S CALL TO DETERMINE THE DYNAMICS AND COUPLING OF THE EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS. WE WILL QUANTIFY THE LINK BETWEEN LCSS IN THE MESOSPHERE AND THE EPP IE USING A MODEL THAT ASSIMILATES OBSERVATIONS FROM THE THERMOSPHERE IONOSPHERE MESOSPHERE ENERGETICS AND DYNAMICS (TIMED) AND AERONOMY OF ICE IN THE MESOSPHERE (AIM) SATELLITES IN NASA'S HELIOPHYSICS SYSTEM OBSERVATORY. UNDERSTANDING THE EXTENT TO WHICH EPP-NOX ACTS AS A VERTICAL COUPLING AGENT BY INTERFERING WITH CATALYTIC OZONE LOSS PROCESSES DIRECTLY SUPPORTS NASA HELIOPHYSICS GOAL TO UNDERSTAND OUR ATMOSPHERE S RESPONSE TO EPP AND ASSOCIATED EFFECTS ON NO AND O3 . THE WHOLE ATMOSPHERE COMMUNITY CLIMATE MODEL WITH THERMOSPHERE AND IONOSPHERE EXTENSION (WACCM-X) A COMPREHENSIVE NUMERICAL MODEL FROM THE SURFACE THROUGH THE THERMOSPHERE WILL BE USED FOR THIS INVESTIGATION. WE WILL INCORPORATE SATELLITE DATA FROM THE SOUNDING OF THE ATMOSPHERE USING BROADBAND EMISSION RADIOMETRY (SABER) MICROWAVE LIMB SOUNDER (MLS) AND SOLAR OCCULTATION FOR ICE EXPERIMENT (SOFIE) INSTRUMENTS. OUR QUESTIONS WILL BE ANSWERED VIA THE FOLLOWING EXPERIMENTS: DIAGNOSE LCSS NEAR THE POLAR WINTER MESOPAUSE IN WACCM-X DATA ASSIMILATION RESEARCH TESTBED (DART) A MODEL VERSION WHERE THE STRATOSPHERE AND MESOSPHERE ARE CONSTRAINED BY SABER AND MLS SATELLITE OBSERVATIONS. COMPARE LCS PROPERTIES WHERE THE MODEL IS FREE-RUNNING TO SABER MLS AND SOFIE. ) ANALYZE SOFIE PROFILES ACROSS THE EDGE OF LCSS AS A FUNCTION OF TIME TO ASSESS WHETHER STRONGER DOWNWARD TRANSPORT OCCURS ON THE INTERIOR.