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We examine a Dipolarization Front (DF) event with an embedded electron diffusion region (EDR), observed by the Magnetospheric Multiscale (MMS) spacecraft on 08 September 2018 at 14:51:30 UT in the Earth's magnetotail by applying multi‐scale multipoint analysis methods. In order to study the large‐scale context of this DF, we use conjunction observations of the Cluster spacecraft together with MMS. A polynomial magnetic field reconstruction technique is applied to MMS data to characterize the embedded electron current sheet including its velocity and the X‐line exhaust opening angle. Our results show that the MMS and Cluster spacecraft were located in two counter‐rotating vortex flows, and such flows may distort a flux tube in a way that the local magnetic shear angle is increased and localized magnetic reconnection may be triggered. Using multi‐point data from MMS we further show that the local normalized reconnection rate is in the range of R ∼ 0.16 to 0.18. We find a highly asymmetric electron in‐ and outflow structure, consistent with previous simulations on strong guide‐field reconnection events. This study shows that magnetic reconnection may not only take place at large‐scale stable magnetopause or magnetotail current sheets but also in transient localized current sheets, produced as a consequence of the interaction between the fast Earthward flows and the Earth's dipole field. Plain Language Summary: Magnetic Reconnection is a key energy conversion process, where magnetic energy is converted into kinetic energy of plasma particles. During this process the magnetic field topology changes and the plasma particles decouple from the magnetic field in the so‐called diffusion region and get accelerated, forming a fast outflow jet. Over the last decades, hints arise that reconnection can take place at many different places in the magnetosphere and also very locally and intermittently. Fast plasma flows in the Magnetotail, moving toward the Earth, are assumed to be a consequence of magnetic reconnection, and are often accompanied by dipolar‐shaped magnetic flux bundles, embedded into them. The leading edges of such flux bundles are called dipolarization fronts (DF). In this work, we investigate a DF event, which hosts a diffusion region. First, we study the large‐scale characteristics of the DF, by utilizing data from both the Magnetospheric Multiscale (MMS) and the Cluster mission, that observe different regions of the event almost simultaneously. Second, we performed a 3D magnetic field reconstruction technique and compared the results to MMS data, to investigate the event on small scales. Key Points: A thin current sheet inside a dipolarization front, embedded in a diverging flow is analyzed using a polynomial reconstruction techniqueTransient reconnection event is detected in a high magnetic shear region, where the magnetic field is deflected due to duskward fast plasma flowThe reconstructed current sheet has a guide field of ∼1.8 the reconnecting component with normalized reconnection rate between 0.16 and 0.18 [ABSTRACT FROM AUTHOR]

The present study is focused on the problem of reconstruction of the magnetic configuration in the magnetic reconnection electron diffusion region (EDR). The problem is addressed in the frame of electron magnetohydrodynamics with kept electron inertia term. We introduce the new reconstruction model independent of divergence of the electron pressure tensor and reconnection electric field. The model is tested on the magnetotail reconnection event of July 11, 2017 observed by the Magnetospheric Multiscale (MMS) spacecraft in the course of crossing the very core part of the reconnection region, the internal EDR. This new model demonstrates considerably better accuracy of the longitudinal electron velocity reconstruction due to the lower sensitivity to the configuration deviation from the two‐dimensional time‐independent model adopted in our study. We suggest also a new technique to estimate the guide field, implementing the reconstruction of magnetic potential of the in‐plane magnetic field and relying on symmetric properties of magnetic reconnection. Plain Language Summary: Magnetic reconnection is a fundamental plasma process responsible for the magnetic field reconfiguration and transforming magnetic energy to kinetic and thermal energy of plasma. In the Earth's magnetosphere, the magnetospheric conditions are monitored by several spacecraft missions. Among them, the NASA Magnetospheric Multiscale (MMS) mission is designed for exploring the process of reconnection. On July 11, 2017 at about 22:34 UT MMS was located in the magnetotail at a very fortunate position, intersecting the reconnection region in its very central part, the so‐called electron diffusion region (EDR). Since MMS consists of four identical spacecraft, MMS provides an excellent tool for testing analytical models of reconnection. Taking the data of one probe as the boundary condition for the analytical model, one can compare the results of calculations with other probes data. In the present paper we suggest a new model of EDR, and compare it to the existing one using the data of 2017/07/11 event. This comparison has shown that the electron inertia term plays an important role in the EDR physics; the proper handling of this term allows considerable improvement of the EDR reconstruction accuracy. Key Points: A model for electron diffusion region (EDR) reconstruction in electron magnetohydrodynamics (EMHD) approximation with kept electron inertia is developedReconstruction of the out‐of‐plane magnetic field is performed independent of the reconnection electric field and pressure anisotropyReconstruction is applied for self‐consistent estimate of the guide field value and local coordinate system orientation [ABSTRACT FROM AUTHOR]