Constraining the Location of the Outer Boundary of Earth's Outer Radiation Belt

Characterizing the location of outer boundary radiation belt is a key aspect improving models and helps to constrain our understanding mechanisms by which source seed electron populations are transported into belts. In this paper, we hypothesize that there statistical differences in distribution function across boundary, thus analyze flux data from THEMIS (Time History Events Macroscale Interactions during Substorms) satellites identify location. We validate hypothesis using modeled L* values approximately characterize between functions inside outside Initially, perform simple analysis studying radial evolution functions. This approach does not yield clear discontinuity, highlighting need for more complex treatment data. Subsequently, employ machine learning (with no dependence on position or L*) test range candidate locations. By analyzing performance at each location, ≈8 RE, with results suggesting some variability. typically further out than those used current models.