Kinetic-scale Flux Rope in the Magnetosheath Boundary Layer

Abstract

We here present a new type of kinetic-scale (∼1 ion gyroradius) flux rope (KFR) in the Earth's dayside magnetosheath boundary layer with Magnetospheric Multiscale high temporal cadence data. This structure exhibits a slight twist of magnetic field that is possibly generated by a field-Aligned current, which differs from typical dayside flux ropes usually observed within the current sheet where magnetic reconnection can occur. The perpendicular electron fluxes within 19-52 eV are increased ∼10% inside the KFR. Detailed analysis shows that these perpendicular electrons may encounter their mirror point (at the position of the KFR, strong field region) when traveling from the magnetosheath toward the ionosphere and will be reflected to the magnetosheath. A possible scenario is that this KFR is different from previous flux ropes that transfer electron flux to the magnetosphere but could intercept magnetosheath large pitch angle electron flux to the magnetosphere.