Abstract A model balancing diffusive field‐line curvature (FLC) scattering loss with other local source, loss, and transport processes is used to compute the L‐shell location of the proton radiation belt outer boundary, where intensity falls below observable levels. The FLC scattering rate increases with increasing L and proton energy, decreasing equatorial pitch angle, and increasing geomagnetic activity, as determined with the Kp‐dependent T89 external magnetic field combined with a dipole internal field. Simulated proton intensity near the outer boundary is compared to measurements from both the low‐altitude SAMPEX satellite and the high‐altitude Van Allen Probes satellites, with correction for instrumental biases caused by field‐of‐view, energy range, and the east‐west effect. Good agreement between observations and simulations is obtained for average boundary locations, time‐dependent variations caused by magnetic storms, and average equatorial pitch‐angle distributions.
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