Geometric interpretation of electromagnetic memory and large gauge transformation

We develop a geometric characterization of electromagnetic memory in terms of the optical data of charged-particle congruences. We derive the worldline deviation of charged particles near null infinity for both massless and massive particles and construct the corresponding optical data. We show that the asymptotic shear of the charged-particle congruence provides an equivalent encoding of electromagnetic memory and its associated large gauge transformation. This establishes a geometric interpretation of electromagnetic memory and large gauge transformations in terms of the asymptotic evolution of charged-particle congruences.