When the magnetic field lines of the Earth and the interplanetary magnetic field lines (IMF) of the sun are anti-parallel, they may reconnect and the previously closed terrestrial field lines become open and are tied to the solar wind. These open magnetic field lines are dragged towards the nightside by the solar wind, forming the elongated magnetotail, where they accumulate. The accumulation of magnetic field lines in the stretched tail yields a surplus of magnetic energy, which is subsequently (explosively) converted into kinetic energy by the so-called magnetic reconnection. This causes a prompt rearrangement of the magnetic field lines from a previously open to a closed configuration. Since the closed magnetic field lines are still stretched, the stored magnetic energy is released through the magnetic tension force, accelerating the close field lines earthward together with the plasma. This process, from a stretched to a more dipolar field configuration, is called the magnetotail dipolarization. Magnetotail dipolarizations are a key ingredient in the mass, energy and flux transport in the Earth's magnetotail. The main aim of this thesis is to obtain a better understanding of the magnetic field dipolarization process, and how these short-duration high-speed plasma flows, so-called bursty bulk flows (BBFs), together with the front-like magnetic field dipolarizations (dipolarization fronts, DFs), transfer the flux from the distant tail towards the Earth. Therefore, the in-situ measurements of the magnetic field and plasma by the Cluster and Magnetospheric Multiscale (MMS) multi-spacecraft missions are used. The results suggest that DFs are kinetic structures, on the order of one ion gyroradius/inertial length. They can be considered as small vertical current sheets, in which the currents mainly flow perpendicular to the magnetic field. Furthermore, DFs tend to be tangential discontinuities in an early stage after reconnection, separating an energetic, tenuous plasma population from the ambient plasma sheet population. As a consequence of the zero mass flow across a tangential discontinuity a local flux pile-up ahead of the DF takes place as the DF moves earthward. We find a higher magnetic flux in front of fast moving DFs. Closer to the Earth, the plasma population before and after the DFs converge, and the DFs start to brake and become unstable, disordered structures.