  We investigate the (conformally coupled) scalar field on a general Carrollian
spacetime in arbitrary dimension. The analysis discloses electric and magnetic
dynamics. For both, we provide the energy and the momenta of the field,
accompanied by their conservation equations. We discuss the conservation and
non-conservation properties resulting from the existence of conformal
isometries and the associated charges. We illustrate those results for a scalar
field propagating on the null boundary of four-dimensional Ricci-flat
Robinson--Trautman spacetimes.
