The location and rate of occurrence of near-Earth magnetotail reconnection as observed by Cluster and Geotail

A statistical characterization of the location and rate of occurrence of magnetic reconnection in the near-Earth magnetotail is performed by analyzing the set of ion diffusion region (DR) observations made by the Cluster and Geotail spacecraft during solar maximum and the declining phase. The occurrence rate is analyzed in terms of its dependence on both XGSM⁎XGSM⁎ and YGSM⁎YGSM⁎ (where coordinates are in the solar wind aberrated geocentric solar magnetospheric system). Within the limits of the statistics available to this study, we find the purely XGSM⁎-dependentXGSM⁎-dependent occurrence rate to be roughly constant over a large portion of the near-Earth magnetotail. In contrast, we find the purely YGSM⁎-dependentYGSM⁎-dependent occurrence rate to be biased towards dusk with a local maximum between 0RE≤YGSM⁎≤5RE. The YGSM⁎-dependentYGSM⁎-dependent occurrence rate is then used to construct a quasi-2D formulation of the DR occurrence rate, which has explicit dependence on XGSM⁎XGSM⁎ and implicit dependence on YGSM⁎YGSM⁎. The quasi-2D occurrence rate is then used to examine the predicted ephemeris of the Magnetospheric MultiScale (MMS) spacecraft. We estimate that, during its near-Earth magnetotail survey phase, MMS will likely observe 11±4 DR events.

• Cluster and Geotail observations of the nightside ion diffusion region are analyzed.
• The occurrence rate of events is calculated as a function of XGSM and YGSM.
• The occurrence rate is used to estimate the number of events MMS will observe.