The photometric scans of the plasma tail of Comet Halley are compared with the profiles of brightness distribution for the tail streams of which were calculated with the use of the diffusion model of the plasma tail We estimated the magnetic field induction and the lifetime of ions in the tail of Comet Halley as well as the coefficients of diffusion during the observations al time. It is shown that the jump of the magnetic field induction in the plasma tail can be a result of a collision of the comet with a highstream solar wind.