Analysis of the 3-D shape of the terrestrial bow shock by interball/magion 4 observations

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Location and shape of the terrestrial bow shock are analyzed using MAGION 4 (sub satellite of INTERBALL 1) crossings of this boundary and upstream solar wind parameters measured by the WIND spacecraft. Different crossing points were mapped to the Sun — Earth line and to the terminator plane using an analytical model of the planetary bow shock previously developed for the Martian bow shock investigation. Analysis of the subsolar bow shock position as a function of Alfvenic Mach number ( M a ) revealed fine effect that this boundary tends to approach the Earth when M a is decreasing for field-aligned flow of the solar wind, while for non field-aligned flow the bow shock moves away from the planet. Asymmetry of the terrestrial bow shock in the terminator plane is found for non field-aligned flow with anisotropic Friedrichs diagrams.