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

This paper presents a comprehensive study of the intense current structures (ICSs) at the dayside magnetopause, by using the high‐resolution data from the Magnetospheric Multiscale (MMS) mission. About 3,600 ICSs with a current density exceeding 1.2 μA/m2 have been detected within the magnetopause boundary layer (MBL). We find that most ICSs crossed the spacecraft in less than 1 s, corresponding to an average thickness of less than one ion inertial length (di). The number of ICSs decreases with the thickness increasing from the electron‐scale to the ion‐scale. Boundary layers closer to Earth have more ICS than boundary layers further away from Earth, probably caused by the large solar wind dynamic pressure. The occurrence rate of the ICS is higher in the dusk sector near the meridian. For most ICSs, the current is carried by electrons. The perpendicular current (90° to the magnetic field) is larger than the parallel current (0° or 180° to the magnetic field) for more ICSs. The energy conversion between the magnetic field and plasma as measured by J·E $\boldsymbol{J}{\dot{}}\boldsymbol{E}$ is primarily through the perpendicular current and electric field, while the energy dissipation J·E′=J·(E+Ve×B) $\boldsymbol{J}{\dot{}}{\boldsymbol{E}}^{\prime }=\boldsymbol{J}{\dot{}}(\boldsymbol{E}+{\boldsymbol{V}}_{\boldsymbol{e}}\times \boldsymbol{B})$ 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. Plain Language Summary Current sheet is the hotbed for various instabilities and an important site for energy exchange between electromagnetic fields and plasmas. Current structures with electric current density exceeding 1 μA/m2 have frequently observed by the Magnetospheric Multiscale mission at the dayside magnetopause boundary layer. Important features of these intense current structures, such as the occurrence rate, current carrier, contribution to energy conversion, are not clear. This paper presents a comprehensive analysis of more than three thousand intense current structures at the magnetopause. We show that most of these current structures are extremely short in time domain and have thicknesses less than the ion inertial length. Moreover, they play important roles in energy dissipation within the boundary layer. These results are of great h