  Context. Converging flows with strong magnetic fields of different polarity
can accelerate particles through magnetic reconnection. If the particle mean
free path is longer than the reconnection layer is thick, but much shorter than
the entire reconnection structure, the particle will mostly interact with the
incoming flows potentially with a very low escape probability. Aims. We
explore, in general and also in some specific scenarios, the possibility of
particles to be accelerated in a magnetic reconnection layer by interacting
only with the incoming flows. Methods. We characterize converging flows that
undergo magnetic reconnection, and derive analytical estimates for the particle
energy distribution, acceleration rate, and maximum energies achievable in
these flows. We also discuss a scenario, based on jets dominated by magnetic
fields of changing polarity, in which this mechanism may operate. Results. The
proposed acceleration mechanism operates if the reconnection layer is much
thinner than its transversal characteristic size, and the magnetic field has a
disordered component. Synchrotron losses may prevent electrons from entering in
this acceleration regime. The acceleration rate should be faster, and the
energy distribution of particles harder than in standard diffusive shock
acceleration. The interaction of obstacles with the innermost region of jets in
active galactic nuclei and microquasars may be suitable sites for particle
acceleration in converging flows.
