Multi-scale coupling during magnetopause reconnection: the interface between the electron and ion diffusion regions
arXiv:2003.03010 · doi:10.1029/2020JA027985
Abstract
Magnetospheric Multiscale (MMS) encountered the primary low-latitude magnetopause reconnection site when the inter-spacecraft separation exceeded the upstream ion inertial length. Classical signatures of the ion diffusion region (IDR), including a sub-ion-Alfvénic de-magnetized ion exhaust, a super-ion-Alfvénic magnetized electron exhaust, and Hall electromagnetic fields, are identified. The opening angle between the magnetopause and magnetospheric separatrix is . The exhaust preferentially expands sunward, displacing the magnetosheath. Intense pileup of reconnected magnetic flux occurs between the magnetosheath separatrix and the magnetopause in a narrow channel intermediate between the ion and electron scales. The strength of the pileup (normalized values of 0.3-0.5) is consistent with the large angle at which the magnetopause is inclined relative to the overall reconnection coordinates. MMS-4, which was two ion inertial lengths closer to the X-line than the other three spacecraft, observed intense electron-dominated currents and kinetic-to-electromagnetic-field energy conversion within the pileup. MMS-1, 2, and 3 did not observe the intense currents nor the particle-to-field energy conversion but did observe the pileup, indicating that the edge of the generation region was contained within the tetrahedron. Comparisons with particle-in-cell simulations reveal that the electron currents and large inclination angle of the magnetopause are interconnected features of the asymmetric Hall effect. Between the separatrix and the magnetopause, high-density inflowing magnetosheath electrons brake and turn into the outflow direction, imparting energy to the normal magnetic field and generating the pileup. The findings indicate that electron dynamics are likely an important influence on the magnetic field structure within the ion diffusion region.
Submitted to the Journal of Geophysical Research: Space Physics
References in corpus (15)
- Two-scale structure of the electron dissipation region during collisionless magnetic reconnection
- Why does steady-state magnetic reconnection have a maximum local rate of order 0.1?
- Kinetic signatures of the region surrounding the X-line in asymmetric (magnetopause) reconnection
- A Review of the 0.1 Reconnection Rate Problem
- Magnetospheric Multiscale Dayside Reconnection Electron Diffusion Region Events
- The Effects of Turbulence on Three-Dimensional Magnetic Reconnection at the Magnetopause
- Universality of lower hybrid waves at Earth's magnetopause
- Enhanced Electron Mixing and Heating in 3D Asymmetric Reconnection at the Earth's Magnetopause
- The effect of a guide field on local energy conversion during asymmetric magnetic reconnection: MMS observations
- Turbulence in Three-Dimensional Simulations of Magnetopause Reconnection
- MMS observation of asymmetric reconnection supported by 3-D electron pressure divergence
- Localized Oscillatory Dissipation in Magnetopause Reconnection
- Orientation and stability of asymmetric magnetic reconnection x-line
- Orientation of x-lines in asymmetric magnetic reconnection - mass ratio dependency
- On the collisionless asymmetric magnetic reconnection rate