IMF control of the location of Venusian bow shock: The effect of themagnitude of IMF component tangential to the bow shock surface

摘要

The interplanetary magnetic field (IMF) frozen in the solar wind, together with the solar EUV radiation, can significantly affect the location of Venusian bow shock. To recognize the IMF effect on the Venusian bow shock, we investigated 1680 bow shock crossings recorded by Venus Express during the unusually long-lasting solar minimum (May 2006 to December 2010), of which the effect of solar EUV variation was significantly decreased. Our analysis shows that during the unusually long-lasting solar minimum, the effect of the solar EUV flux on the Venusian bow shock location is negligible. Neither solar wind dynamic pressure nor solar wind velocity has observable effect on the Venusian bow shock location. However, the IMF magnitude has a strong control of the Venusian bow shock location. We found that the size of Venusian bow shock linearly increases with the magnitude of the IMF component tangential to the bow shock surface, and this relationship can account for the perpendicular-parallel asymmetry and magnetic pole-equator asymmetry found in previous researches, as well as the magnetic dawn-dusk asymmetry discerned in this study.