ИСТИНА

The properties of pickup helium ions in a vicinity of the neutral helium focusing cone is studied numerically. The transport of the ions is described by the Fokker-Planck type equation for the anisotropic velocity distribution function, which takes into account pitch-angle scattering, adiabatic cooling and focusing in the interplanetary magnetic field, and energy diffusion. The solar wind parameters, which are used in the numerical model, correspond to the most recent very quiet solar minimum starting in 2007. We show that the pickup helium ion focusing cone measured with spacecraft during this period of time can be shifted in ecliptic longitude relative to the neutral helium cone, and thus can not be considered as an implicit indicator of the interstellar flow direction. The value of the shift depends on the mean free path of pickup ions. The larger is the mean free path, the larger is the shift.