THE EARTHS BOW SHOCK AND MAGNETOPAUSE POSITION AS A RESULT OF THE SOLAR WIND-MAGNETOSPHERE INTERACTION

The paper deals with a study of the variations of the Earth's magnetopause and the bow shock position based on simultaneous measurements by the Prognoz 10 and IMP-8 spacecraft. The real boundary position determined by one spacecraft has been compared with the boundary position calculated from Formisano's model. The solar wind parameters, required for the calculation, have been taken from measurements of the other spacecraft. The differences between the calculated and observed boundary positions are discussed from the point of view of possible influences of different solar wind parameters on these deviations. From our discussion it follows that the magnetopause shape calculated by OLSON [(1962), The shape of the tilted magnetopause. J. geophys. Res. 74, 5642.], FAIRFIELD [(1971), Average and unusual location of the Earth's magnetopause and bow shock. J. geophys. Res. 76, 6700.] or CHOE et al. [(1973), Precise calculation of the magnetosphere surface for a tilted dipole. Planet. Space Sci. 21, 485.] for a dipole magnetic field seems to be a better approximation than Formisano's three-dimensional fit. On the other hand, Formisano's fit to the bow shock shape can be used for determination of the bow shock position if the additional influence of the interplanetary magnetic field strength is taken into account.