Observations of Relativistic and Ultra-Relativistic Electron Bursts in Earth's Magnetotail: The Role of Magnetic Reconnection in Electron Acceleration

Magnetic reconnection is a fundamental process driving charged particle acceleration in space plasma environments. Traditionally, theoretical and simulation models of this acceleration are validated using in-situ spacecraft measurements from reconnection regions in the near-Earth magnetosphere. In this presentation, we showcase observations revealing that electron acceleration during reconnection can be far more efficient than previously estimated, producing electron populations with energies reaching several MeV. Remarkably, these bursts occur even in regions where the thermal electron energies are below 1 keV. These observations, made possible by recent low-altitude CubeSat missions monitoring magnetotail electron fluxes, provide new insights into the mechanisms driving electron acceleration in Earth's magnetotail.