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We report observations of a Bursty Bulk Flow (BBF) penetrating close to the outer edge of the radiation belt. The turbulent BBF braking region is characterized by ion velocity fluctuations, magnetic field (B) variations, and intense electric fields (E). In this event, energetic (>100 keV) electron and ion fluxes are appreciably enhanced. Importantly, fluctuations in energetic electrons and ions suggest local energization. Using correlation distances and other observed characteristics of turbulent E, test-particle simulations support local energization by E that favors higher-energy electrons and leads to an enhanced energetic shoulder and tail in the electron distributions. The energetic shoulder and tail could be amplified to MeV energies by adiabatic transport into the radiation belt where |B| is higher. This analysis suggests that turbulence generated by BBFs can, in part, supply energetic particles to the outer radiation belt and that turbulence can be a significant contributor to particle acceleration.

We present observations that suggest the X-line of guide-field magnetic reconnection is not necessarily orthogonal to the plane in which magnetic reconnection is occurring. The plane of magnetic reconnection is often referred to as the L–N plane, where L is the direction of the reversing and reconnecting magnetic field and N is normal to the current sheet. The X-line is often assumed to be orthogonal to the L–N plane (defined as the M-direction) in the majority of theoretical studies and numerical simulations. The four-satellite Magnetospheric Multiscale (MMS) mission, however, observes a guide-field magnetic reconnection event in Earth’s magnetotail in which the X-line may be oblique to the L–N plane. This finding is somewhat opportune as two of the MMS satellites at the same N location report nearly identical observations with no significant time delays in the electron diffusion region (EDR) even though they have substantial separation in L. A minimum directional derivative analysis suggests that the X-line is between 40° and 60° from M, adding support that the X-line is oblique. Furthermore, the measured ion velocity is inconsistent with the apparent motion of the MMS spacecraft in the L-direction through the EDR, which can be resolved if one assumes a shear in the L–N plane and motion in the M-direction. A nonorthogonal X-line, if somewhat common, would call for revisiting theory and simulations of guide-field magnetic reconnection, reexamination of how the reconnection electric field is supported in the EDR, and reconsidering the large-scale geometry of the X-line.

We examine a rare and interesting observation of magnetic reconnection embedded in a large-scale region of strong turbulence in which magnetic field annihilation is energizing ions and electrons. The magnetic reconnection event is in Earth’s magnetotail and is associated with enhanced energetic particle fluxes indicating local particle acceleration. Despite substantial electric and magnetic field fluctuations throughout the surrounding, large-scale region, the ongoing magnetic reconnection has many similar properties to laminar, 2D magnetic reconnection including Hall electric fields, Hall magnetic fields, a thin electron current sheet, and ion and electron jets. Notably, the electron jet emerging from the electron diffusion region (EDR) appears to transport sufficient off-diagonal momentum to infer that off-diagonal electron stress can support the reconnection electric field in the EDR even in a turbulent environment. Although the electron jet appears to be briefly (∼1 s) deflected or possibly interrupted by an electromagnetic disturbance, the reconnection appears to otherwise continue for a long period (∼30 minutes) as evidenced by a persistent ion jet. This particular finding implies that the fundamental electron-scale processes inside of the EDR in turbulent magnetic reconnection are not necessarily distinct from those in laminar magnetic reconnection. These observations provide direct confirmation that magnetic reconnection can not only be responsible for but also can continue in regions of large-scale turbulence. Because the electric and magnetic fields of strong turbulence are linked to particle acceleration, it follows that particle acceleration also can continue as a consequence of turbulent magnetic reconnection.