Statistics of the Intense Current Structure in the Dayside Magnetopause Boundary Layer

This paper presents a comprehensive study of the intense current structure (ICS) at the dayside magnetopause, by using the high-resolution data from the Magnetospheric Multiscale (MMS) mission. About 3,600 ICSs with current density exceeding 1.2 μA/m2 have been detected during phase 1a and 1b within the magnetopause boundary layer (MBL). We find that most ICSs have a temporal duration of less than 1 second and thickness of less than one ion inertial length. The number of ICSs decreases with the thickness increasing from the electron-scale to the ion-scale. The occurrence rate of the ICS is relatively higher close to Earth and in the dusk sector near the meridian, probably caused by the large solar wind dynamic pressure. In a local boundary normal coordinate system, the occurrence rate is higher on the magnetosheath side. For most ICSs, the current is carried by electrons. The perpendicular current is larger than the parallel current for more ICSs. The energy conversion J·E is primarily through the perpendicular current and electric field, while the non-ideal energy conversion J·E’ is mainly dominated by the parallel component. ICSs provide much stronger energy conversion and dissipation compared to the ambient plasma in the MBL. This study improves our understanding of the characteristics of the ICS and its role in solar wind-magnetosphere coupling.