Magnetic monopoles and neutron stars

A magnetic monopole in the interstellar medium can be accelerated near a neutron star by its huge magnetic field. It would acquire an energy of approx.1020 eV and collide with the star surface. We consider the possibility of the production of secondary monopoles and antimonopoles by this incident monopole interacting with the star material. These secondary monopoles are also accelerated by the magnetic field, and it is shown that they can produce other secondary monopoles, and so on, giving an avalanche of monopoles. This process, which could be effective for monopoles with a mass up to approx.105 GeV/c2, would lead to the extinction of the star magnetic field. Furthermore, the number of secondary monopoles injected in the interstellar medium is high enough for some of them to interact with other neutron stars. The avalanche phenomenon would then propagate from neutron star to neutron star until all of them in the Galaxy are demagnetized, and this within a time scale of approx.105 years. Highly magnetized neutron stars are observed, therefore, (i) either the density of magnetic monopoles in the interstellar medium is strikingly low (many orders of magnitude below the present upper limits) or (ii) the magnetic monopoles do not produce secondary monopoles while interacting with matter, above a certain level which is determined