Magnetic Hump Associated with Electron Vortex at Dipolarization Front

Abstract

As the plasma boundary between two distinct plasma populations, dipolarization fronts (DFs) host abundant kinetic-scale substructures that change their normal directions and thus cause their deformation. However, studies on such deformation caused by an electron vortex have been lacking. Here, we present novel observations of a subion-scale magnetic hump (MHu) associated with an oblique electron vortex at a DF through strengthening three components of the magnetic field. A radial electric field in the MHu, showing bipolar variation, is also associated with the electron vortex as it is mainly ascribed to the electron convection term. There is apparent energy conversion ( $\overrightarrow{J}\cdot \overrightarrow{E}$ ∼−0.3 nw m ^−3 ) from the particles to the electromagnetic field in the MHu’s leading part, which is accompanied by inflow and outflow of electromagnetic energy (nonzero ${\rm{\nabla }}\cdot \overrightarrow{S}$ ). The other regions of the DF host opposite energy conversion ( $\overrightarrow{J}\cdot \overrightarrow{E}$ > 0). Broadband parallel electrostatic waves are also observed in the MHu. Our study provides insights into the kinetic-scale processes at DFs.

Keywords

• Space weather
• Space plasmas
• Planetary magnetospheres