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Magnetic reconnection, a process characterized by the mixing of distinct magnetic flux tubes within a magnetized plasma, results in the exchange of energy between the electromagnetic fields of these flux tubes and the confined plasma. This phenomenon is observed across various astrophysical entities, playing a pivotal role in the energization and global transport of plasma. On Earth, magnetic reconnection is integral to the dynamics of the magnetotail, facilitating the depressurization of the tail during earthward convection, markedly elevating the temperature of magnetotail plasma, and generating field-aligned particle beams that pro- mote wave generation and growth. Observations across the magnetotail and under varying levels of geomagnetic activity have demonstrated magnetic reconnection’s importance and prevalence. It significantly influences global magnetospheric plasma energy transport during both quiescent and active periods through episodic magnetic reconnection events that pro- pel heated plasma ejecta in both earthward and tailward directions. Given its central role in global plasma transport and energization within the magnetotail this Ph.D. thesis seeks to elucidate key aspects of magnetotail reconnection to enhance our understanding of the magnetotail’s evolution.Investigating the dynamics of magnetotail reconnection presents a multifaceted challenge. This Ph.D. thesis leverages ongoing inner-magnetosphere missions and advanced magnetic field models to dissect three critical aspects of this issue. 1) Assess whether global plasma convection during geomagnetic storms is influenced by intermittent or quasi-continuous mag- netotail reconnection. While prior studies have primarily concentrated on relatively quiet conditions, revealing two distinct plasma transport modes in the magnetotail—substorms characterized by irregular reconnection at approximately 25-30 Earth radii (RE) and steady magnetospheric convection featuring more consistent reconnection beyond 40 RE —a detailed investigation during intense storm conditions is notably absent. This analysis aims to cate- gorize magnetotail reconnection during storms as either intermittent or continuous, offering significant insights into energy transport mechanisms under such conditions. 2) Examine the frequency and impact of near-Earth magnetotail reconnection during storms, a phenomenon less understood compared to non-storm conditions traditionally located beyond 25 RE. With the recent solar cycle prompting more frequent storms, emerging evidence supports the oc- currence of very-near-Earth reconnection (VNERX). This study explores VNERX events and their contribution to storm dynamics. 3) Study the heating processes that take place during magnetotail reconnection. Simulations and observations show that most of the par- ticle energy gained through reconnection is in the form of thermal energy. In the near-Earth tail, gradients in plasma pressure can transfer the kinetic energy from reconnection ejecta into plasma heat far away from the x-line. However, in the mid-tail, where reconnection occurs most frequently, these gradients are diminished. We study whether particle heating is still significant in magnetotail reconnection at these distances, and what factors control that heating. The heating process of mid-tail reconnection has important implications towards understanding the thermal profile of the plasma sheet, a major source of plasma for the inner magnetosphere and the storm-associated ring current.

We review recent studies of magnetotail flow bursts and their connection to the inner magnetosphere. The flow bursts are propelled by the curvature force of the dipolarizing flux bundles released by tail reconnection. They energize the inner edge of the plasma sheet at times of substorms, drive substorm field-aligned currents, and cause particle injections, plasma waves, and particle precipitation. These flow bursts do not enhance the ring current significantly at non-storm times (by definition), but they are a critical aspect of substorm dynamics - they are observed to stop outside geosynchronous altitude [Sergeev et al., JGR, 2012]. Storm main phase flow bursts also tend to stop prior to arriving at the geosynchronous region [Runov et al., JGR, 2021]. During storms, only some flow bursts have been found to be initiated at a very-near Earth reconnection site (closer than 13 Earth radii) and those only occur during the main phase [Beyene et al., JGR, 2023 in prep.]. During storms, while there exist numerous transient enhancements of an otherwise elevated AE index, there are very few embedded substorm-like intervals. Early work [Kissinger et al., JGR, 2014] also suggests that steady magnetospheric convection (SMC) intervals during storms cause enhancements of relativistic electrons in the inner magnetosphere. However, neither substorms nor SMCs are common during storms [Beyene et al., JGR 2022]. Here we explore how the intermittent, fast flows from tail reconnection might have access to the near-Earth during storms and how they may power the ring current., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)