  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.
