2009/09/22 by P. Jean, W. Gillard, Alexandre Marcowith +2
Physics and Astronomy · #Advection #Annihilation #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Computational physics #Cosmic ray #Dark Matter and Cosmic Phenomena #Electron #Galaxy #Interstellar medium #Magnetic field #Magnetohydrodynamic drive #Magnetohydrodynamics #Monte Carlo method #Nuclear physics #Physics #Plasma #Positron #Quantum mechanics #Scattering #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/200809830
18 pages, 12 figures, accepted in Astronomy and Astrophysics
arxiv created 2009/09/22 · openalex publication_date 2009/10/27 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
<i>Aims. <i/>We seek to understand the propagation mechanisms of positrons in the interstellar medium (ISM). This understanding is a key to determine whether the spatial distribution of the annihilation emission observed in our Galaxy reflects the spatial distribution of positron sources and, therefore, makes it possible to place constraints on the origin of positrons.<i>Methods. <i/>We review the different processes that are likely to affect the transport of positrons in the ISM. These processes fall into three broad categories: scattering off magnetohydrodynamic waves, collisions with particles of the interstellar gas, and advection with large-scale fluid motions. We assess the efficiency of each process and describe its impact on the propagation of positrons. We also develop a model of positron propagation, based on Monte-Carlo simulations, which enable us to estimate the distances traveled by positrons in the different phases of the ISM.<i>Results. <i/>We find that low-energy () positrons generally have negligible interactions with magnetohydrodynamic waves, insofar as these waves are heavily damped. Positron propagation is mainly controlled by collisions with gas particles. Under these circumstances, positrons can travel very large distances (up to for 1 MeV positrons) along magnetic field lines before annihilating.