Abstract
This work investigates some aspects of the transport of low-energy positronsin the interstellar medium (ISM). We consider resonance interactions withmagnetohydrodynamic waves above the resonance threshold. Below the threshold,collisions take over and deflect positrons in their motion parallel tomagnetic-field lines. Using Monte-Carlo simulations, we model the propagationand energy losses of positrons in the different phases of the ISM until theyannihilate. We suggest that positrons produced in the disk by an old populationof stars, with initial kinetic energies below 1 MeV, and propagating in thespiral magnetic field of the disk, can probably not penetrate the Galacticbulge.