The influence of the radial IMF on the magnetospheric system

Abstract:

The radial interplanetary magnetic field events are one of the special solar wind conditions when the orientation of IMF is aligned with the solar wind velocity. The radial IMF events usually are regarded as quiet solar conditions, but the unique orientation of the IMF can lead to some consequences in the magnetospheric system. The events are usually accompanied with the low density, temperature, weak magnetic field, and the perturbations of all solar wind parameters are weak. The radial field condition also displaces the foreshock region from the dawn side to cover almost the whole dayside region. The change of the foreshock location causes a highly fluctuating magnetosheath, and these fluctuations can further influence the magnetosphere. We show that when the radial field passes through the bow shock, the tangential components are enhanced and the B_x component also turns to the tangential direction due to draping along the magnetopause. The draped field forms a north-south asymmetric structure outside the magnetopause because the B_z component has different orientation in conjugate hemispheres. The asymmetric field structure will lead to asymmetry of the reconnection location and it further reconstructs the magnetic field structure near the magnetopause and creates a thick boundary layer.