WE PROPOSE TO USE COMBINED MODELING AND DATA ANALYSIS METHODS WITHIN A NOVEL FRAMEWORK OF FIELD-LINE RANDOM WALK TO IMPROVE OUR UNDERSTANDING OF THE LARGE LONGITUDINAL SPREADS OF IMPULSIVE SOLAR ENERGETIC PARTICLE (SEP) EVENTS AS OBSERVED BY MULTIPOINT INSITU SPACECRAFT MEASUREMENTS. COMMONLY THE INTERPLANETARY TRANSPORT OF SEPS IS DESCRIBED BY A KINETIC FOKKER-PLANCK (FP) TYPE OF EQUATION. HOWEVER DUE TO ITS DIFFUSIVE NATURE IN THE PERPENDICULAR TRANSPORT THIS APPROACH FALLS SHORT IN EXPLAINING THE FAST ACCESS OF PARTICLES TO A WIDE RANGE OF LONGITUDES. WE PROPOSE TO EXTEND THE ANALYSIS OF WIDESPREAD SEP EVENTS TO INCLUDE THE EFFECTS OF FIELD-LINE WANDERING IN ORDER TO BETTER UNDERSTAND THE RELEVANT TRANSPORT PROCESSES IN THESE EVENTS. SCIENCE QUESTIONS: IN THIS PROPOSAL WE AIM TO ANSWER THE FOLLOWING SCIENCE QUESTIONS: (1) HOW ARE SEPS ABLE TO QUICKLY ACCESS LONGITUDINALLY WIDELY SEPARATED LOCATIONS IN THE INNER HELIOSPHERE? (2) WHICH ROLE DOES INTERPLANETARY TURBULENCE PLAY IN CROSS-FIELD TRANSPORT OF PARTICLES AND HOW DO SPATIAL VARIATIONS IMPACT ON PARTICLE DISTRIBUTIONS? (3) WHAT IS THE RELATIVE IMPORTANCE OF THE NEAR-SUN INJECTION REGION OF SEPS VS. INTERPLANETARY TRANSPORT EFFECTS FOR THE SPATIAL DISTRIBUTION OF SEPS? (4) HOW ARE ELECTRON ENERGY SPECTRA SHAPED DURING THEIR TRANSPORT FROM COMPACT FLARING REGIONS TO 1AU? METHODS: A COMBINATION OF MODELING AND DATA ANALYSIS WILL HELP TO UNDERSTAND THE SIGNIFICANCE OF DIFFERENT TRANSPORT PROCESSES INVOLVED IN SEP PROPAGATION. WE WILL USE A NOVEL RECENTLY DEVELOPED TRANSPORT MODEL WHICH INCLUDES PARTICLE MOTION ALONG FIELD LINES THAT MEANDER AS A RESULT OF PLASMA TURBULENCE. SUCH A NON-DIFFUSIVE PROPAGATION MODE CAN BE SHOWN TO DOMINATE THE SEP CROSS-FIELD PROPAGATION EARLY IN THE SEP EVENT HISTORY. WE WILL COMPARE THE NEW MODEL RESULTS TO THE STANDARD MODELING USING ONLY A FOKKER- PLANCK EQUATION WITH DIFFUSIVE PERPENDICULAR TRANSPORT USING BOTH IDEALIZED SEP EVENTS AND A DATASET OF SEP OBSERVATIONS. THESE WILL INCLUDE IN-SITU ELECTRON AND ION OBSERVATIONS AND CONTEXTUAL REMOTE OBSERVATIONS OF THE SUN AND SOLAR ATMOSPHERE. RELEVANCE: STUDYING THE TRANSPORT PROCESSES ASSOCIATED WITH ENERGETIC PARTICLES ARRIVING AT EARTH ORBIT IS OF CRITICAL IMPORTANCE FOR SPACE EXPLORATION SINCE SEPS CAN SIGNIFICANTLY INCREASE RADIATION LEVELS IN THE NEAR-EARTH ENVIRONMENT POTENTIALLY DAMAGING TECHNOLOGICAL ASSETS AND IMPACTING ON THE HEALTH AND SAFETY OF HUMANS IN SPACE. OUR PROPOSAL DIRECTLY ADDRESSES THE SCIENCE GOALS OF THE STEREO MISSION ("UNDERSTAND HOW SEPS ARE DISTRIBUTED SO EFFICIENTLY AROUND THE SUN") AND THREE OF THE FOUR DECADAL SURVEY GOALS. THIS RESEARCH IS TIMELY DUE TO THE OBSERVATIONS OF WIDESPREAD SEP EVENTS BY STEREO AND THE UPCOMING SOLAR PROBE PLUS AND SOLAR ORBITER MISSIONS WHICH WILL ADD FURTHER TO OUR OBSERVATIONAL BASIS IN ORDER TO UNDERSTAND ENERGETIC PARTICLE PROPAGATION IN THE INNER HELIOSPHERE.