  We study motion of a relativistic charged particle in a plane slow
electromagnetic wave and background uniform magnetic field. The wave propagates
normally to the background field. Under certain conditions, the resonance
between the wave and the Larmor motion of the particle is possible. Capture
into this resonance results in acceleration of the particle along the wave
front (surfatron acceleration). We analyse the phenomenon of capture and show
that a captured particle never leaves the resonance and its energy infinitely
grows. Scattering on the resonance is also studied. We find that this
scattering results in diffusive growth of the particle energy. Finally, we
estimate energy losses due to radiation by an accelerated particle.
