Galactic Magnetic Field Models Research Articles

Propagation of charged particles from the Galactic Center

Recent analysis of the anisotropy of cosmic rays at 1018 eV (the AGASA and SUGAR data) show significant excesses from regions close to the Galactic Centre and Cygnus. Our aim is to check whether such anisotropies can be caused by a single source of charged particles. We investigate propagation of protons in two models of the Galactic regular magnetic field (with the irregular component included) assuming that the particles are injected by a short lived discrete source lying in the direction of the Galactic Centre. We show that apart from a direct (prompt) image of the source, the regular magnetic field may cause indirect (delayed) images at quite large angular distances from the actual source direction. The observed image is strongly dependent on the time elapsed after ejection of particles and it is also very sensitive to their energies. For the most favourable conditions for particle acceleration by a young pulsar the predicted fluxes are two to four order of magnitudes higher than that observed. The particular numbers depend strongly on the Galactic magnetic field model adopted but it appears that a single pulsar in the Galactic Centre could be responsible for the observed excess.

Images of very high energy cosmic ray sources in the Galaxy: I. A source towards the galactic centre

Recent analyses of the anisotropy of cosmic rays at 1018 eV (the AGASA and SUGAR data) show significant excesses from regions close to the galactic centre and Cygnus. Our aim is to check whether such anisotropies can be caused by single sources of charged particles. We investigate propagation of protons in two models of the galactic regular magnetic field (with the irregular component included) assuming that the particles are injected by a short-lived discrete source lying in the direction of the galactic centre. We show that apart from a prompt image of the source, the regular magnetic field may cause delayed images at quite large angular distances from the actual source direction. The image is strongly dependent on the time elapsed after ejection of particles and it is also very sensitive to their energy. For the most favourable conditions for particle acceleration by a young pulsar, the predicted fluxes are two to four orders of magnitude higher than those observed. The particular numbers strongly depend on the galactic magnetic field model adopted but it seems that a single pulsar in the galactic centre could be responsible for the observed excess.

ULTRA HIGH ENERGY COSMIC RAYS: PROPAGATION IN THE GALAXY AND ANISOTROPY

We considered propagation of Ultra High Energy Cosmic Rays (UHECR) through the galaxy. We investigated models with sources of UHECR distributed in the same way as Cold Dark Matter (CDM) in a self-consistent way, taking into account both extra-galactic and Galactic contributions. Using a very simple toy model of galactic magnetic field we showed that in the case of galactic origin of UHECRs the anisotropy can reach considerable values. In the case of extragalactic UHECRs origin, the anisotropy appears to be nonvanishing only for electron and photon components due to synchrotron losses, but it can hardly be reassured. The reason is an extremely low flux of UHE electrons and a too low level of γ-ray anisotropy.

Propagation of Cosmic Rays from the Vicinity of the Galactic Centre

AbstractThere is now evidence that there may be a strong source of cosmic ray particles in the general direction of the Galactic Centre. The likelihood is that the observed particles are neutrons with energies of about 1018 eV. Associated with the production of those neutrons, we would expect that large numbers of charged cosmic rays would also be produced, and we investigate here the directional properties of those charged particles as they may be observed at the distance of the Earth from the Galactic Centre. We follow the propagation of such particles through a simple Galactic magnetic field model with both a turbulent and a regular field to determine what field properties most affect the observed beam. It appears that the turbulent field component is crucial to any resulting charged particle observations.

Galactic magnetic-field models derived from Faraday-rotation data

The distribution of rotation measures for 86 sources suggests a two-component model for the magnetic field: a disk component directed towardl= 95°, and a component in the local spiral arm, directed alongl= 70° and 250°, with opposite senses above and below the plane. The latter may be due to a looped field in a cloud surrounding the Sun; its net flux is 3·5 micro-gauss.