  We study auto-propulsion of a interface particle, which is driven by the
Marangoni stress arising from a self-generated asymmetric temperature or
concentration field. We calculate separately the long-range Marangoni flow
v^{I} due to the stress discontinuity at the interface and the short-range
velocity field v^{P} imposed by the no-slip condition on the particle surface;
both contributions are evaluated for a spherical floater with temperature
monopole and dipole moments. We find that the self-propulsion velocity is given
by the amplitude of the "source doublet" which belongs to short-range
contribution v^{P}. Hydrodynamic interactions, on the other hand, are
determined by the long-range Marangoni flow v^{I}; its dipolar part results in
an asymmetric advection pattern of neighbor particles, which in turn may
perturb the known hexatic lattice or even favor disordered states.
