2D Reconstruction of Magnetotail Electron Diffusion Region Measured by MMS

• Published in: Geophysical research letters Vol. 49; no. 19
• Main Authors: Schroeder, J. M., Egedal, J., Cozzani, G., Khotyaintsev, Yu. V., Daughton, W., Denton, R. E., Burch, J. L.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.10.2022; American Geophysical Union (AGU)
• Subjects: Aerospace environments; Diffusion; Dynamics; Earth; Electron diffusion; Electrons; Fluid flow; Geomagnetic field; Geomagnetic tail; Image reconstruction; Magnetic field; Magnetic fields; Magnetic reconnection; magnetosphere; magnetotail; Magnetotails; Modelling; Orbital mechanics; reconnection; Simulation; Spacecraft; Three dimensional models; Two dimensional models
• DOI: 10.1029/2022GL100384
• ISSN: 0094-8276; 1944-8007

Models for collisionless magnetic reconnection in near‐Earth space are distinctly characterized as 2D or 3D. In 2D kinetic models, the frozen‐in law for the electron fluid is usually broken by laminar dynamics involving structures set by the electron orbit size, while in 3D models the width of the electron diffusion region is broadened by turbulent effects. We present an analysis of in situ spacecraft observations from the Earth's magnetotail of a fortuitous encounter with an active reconnection region, mapping the observations onto a 2D spatial domain. While the event likely was perturbed by low‐frequency 3D dynamics, the structure of the electron diffusion region remains consistent with results from a 2D kinetic simulation. As such, the event represents a unique validation of 2D kinetic, and laminar reconnection models. Plain Language Summary Magnetic reconnection is a fundamental process that occurs in the near‐Earth space environment with implications for the safety and longevity of space‐borne electronics in which magnetic field lines rearrange and release energy. To understand whether reconnection is better described as occurring in a 2D‐plane without variation in the third direction versus 3D with variation in all directions, we analyze spacecraft data from the night‐side of Earth's magnetic field. We conclude for the considered event that the innermost region, where the field lines reconnect, remains consistent with results from a 2D simulation. Key Points The fluctuating measurements are consistent with a 2D reconnecting geometry, permitting a detailed spacecraft trajectory to be determined The Magnetospheric Multiscale Mission data is projected onto a 2D spatial domain, revealing the fine‐scale structure of the electron diffusion region (EDR) The EDR includes profiles with strong gradients in fields and flows, consistent with those observed in a matched 2D kinetic simulation