Origin of the highest energy cosmic rays and the Galactic halo

The origin of the highest energy cosmic rays, particularly of these with pr imary energies E > 10(20) eV, is a puzzle. Both hypotheses, Galactic and ex tragalactic run into troubles: the former - because of an expected large an isotropy, the latter one - because of energy losses on the microwave backgr ound. Even an 'intermediate' hypothesis, that particles are produced by som e particle objects (e.g. radiogalaxies, AGN's) relatively nearby (closer th an some tens of Mpc) has difficulties as there are no such objects visible (Sigl et al. 1994). Here we are continuing our earlier work (Giller and Zielinska 1995, 1996, 1 997), where we had been considering a possibility that our own Galaxy (in p articular the Galactic Centre) could be the origin site of these high energ y particles. Some conditions, however, would have to occur, which have been not often taken into consideration. These are - a/ a very large magnetic h alo (several tens of kiloparsecs) and b/ a time dependent c.r. activity of the Galactic Centre. In our earlier papers we have shown that under the abo ve conditions the problem of anisotropy is greatly reduced, if not lifted. We consider, however, that in the halo, there was practically only an irreg ular field, with an average value B-in = 2 mu G. In this paper we adopt a m ore realistic halo field, with a regular component in the disc and in the h alo and consider a smaller halo (20 kpc).