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Properties of magnetic reconnection in Earth's magnetotail are determined by prereconnection current sheet characteristics. Although spacecraft observations have revealed that the spatial profiles of two important parameters, density and temperature, across the prereconnection magnetotail current sheet are inhomogeneous, the effects of the inhomogeneities on reconnection processes have received insufficient attention. Using Time History of Events and Macroscale Interactions during Substorm (THEMIS) and Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) observations, we show that the inhomogeneities are ubiquitous throughout the magnetotail. Using particle-in-cell simulations, we demonstrate that strong density inhomogeneity increases magnetotail reconnection rate, and strong temperature inhomogeneity further increases reconnection outflow speed (although reconnection rate does not change significantly). Overall, these inhomogeneities expedite energy conversion efficiency and secondary plasmoid formation during reconnection. As the current sheet density and temperature characteristics vary considerably with geocentric distance and time under different geospace conditions, a large variety of reconnection and postreconnection dynamics results from this dependence.

Plain Language Summary Magnetic reconnection, a fundamental plasma process by which magnetic energy is explosively released to accelerate and heat charged particles via topologic change of magnetic field lines, happens in Earth's magnetotail current sheet. This magnetotail current sheet has inhomogeneous density and temperature profiles across it. We demonstrate that these density and temperature inhomogeneities are important because they exist throughout the magnetotail and control properties of magnetotail reconnection in various aspects.