ИСТИНА

Using the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF) vector, we calculated the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004 and also from 12 to 15 February 2008, when the Cassini spacecraft measured the IMF in the solar wind just upstream of Saturn's dayside bow shock. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively, and also for both strong and moderate IMF magnitudes. It is also shown that the computed open field region in Saturn's southern ionosphere agrees with the poleward boundary of the auroras observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope.