The magnetic configuration of the high-latitude cusp and dayside magnetopause under strong magnetic shears

This paper investigates the structure of the magnetic field near the magnetopause (MP) by analyzing the multiple-point magnetic measurements from the Cluster mission. In this paper, the spatial distribution of the curvature radius of the MP surface at the noon-midnight meridian and for situations with moderate dynamical pressure of solar wind is implied from direct measurements of magnetic field curvature for the first time. The investigation focused on conditions of strong magnetic shear and in which a clear boundary layer is present at the MP. It has been confirmed that the magnetic field lines surrounding the cusp bend sunward at the precusp region and tailward at the postcusp region, implying the existence of a cusp field indentation. The minimum curvature radius of the near-MP field at both precusp and postcusp regions is about 2 R-E. As the latitude decreases, the curvature radius at the MP increases gradually, so that, as the subsolar point is approached, the curvature radius of the MP is nearly equal to the geocentric distance. These results compare well with existing MP models but reveal the limitations inherent in such statistical estimates of local MP curvature, particularly surrounding the cusp regions. The analysis of the magnetic measurements has also verified the existence of the magnetic bottles at both precusp and postcusp regions, which may play a role for the trapping of the charged particles of magnetosphere.