  We study the null asymptotic structure of Einstein-Maxwell theory in
three-dimensional (3D) spacetimes. Although devoid of bulk gravitational
degrees of freedom, the system admits a massless photon and can therefore
accommodate electromagnetic radiation. We derive fall-off conditions for the
Maxwell field that contain both Coulombic and radiative modes with
non-vanishing news. The latter produces non-integrability and fluxes in the
asymptotic surface charges, and gives rise to a non-trivial 3D Bondi mass loss
formula. The resulting solution space is thus analogous to a dimensional
reduction of 4D pure gravity, with the role of gravitational radiation played
by its electromagnetic cousin. We use this simplified setup to investigate
choices of charge brackets in detail, and compute in particular the recently
introduced Koszul bracket. When the latter is applied to Wald-Zoupas charges,
which are conserved in the absence of news, it leads to the field-dependent
central extension found earlier in [arXiv:1503.00856]. We also consider
(Anti-)de Sitter asymptotics to further exhibit the analogy between this model
and 4D gravity with leaky boundary conditions.
