Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail

We report observations of turbulent dissipation and particle acceleration from large‐amplitude electric fields ( E ) associated with strong magnetic field ( B ) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti‐earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally >100 keV, and strong variation. There are numerous occurrences of | E | >100 mV/m including occurrences of large potentials (>1 kV) parallel to B and occurrences with extraordinarily large J · E ( J is current density). In this event, we find that the perpendicular contribution of J · E with frequencies near or below the ion cyclotron frequency ( f ci ) provide the majority net positive J · E . Large‐amplitude parallel E events with frequencies above f ci to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration.