An empirical model for the location and occurrence rate of near-Earth magnetotail reconnection

Abstract

We introduce an empirical model for the location and rate of occurrence of magnetic reconnection in the near-Earth magnetotail. The model is constructed using Geotail data, including the set of diffusion region and fast tailward flow events identified in Nagai et al. (2005). Events are arranged by their X GSM location. The event occurrence profile is normalized by the time spent by Geotail within a distance d of the modeled neutral sheet. To locate the neutral sheet, we use the empirical model of Fairfield (1980). We organize our data via a coordinate system that conforms to the Fairfield neutral sheet model. In this new coordinate system, we calculate the deviation of physical neutral sheet crossings from their Fairfield-model-predicted locations. We equate d to constant multiples of this standard deviation (0.5 RE, 2 R E, and 5 RE). Using these values, we find that our deduced rate of occurrence of reconnection events has a magnitude consistent with those from similar calculations found in the existing literature. We then use our empirical model to analyze the predicted ephemeris for the Magnetospheric Multiscale (MMS) mission. We predict that during its upcoming near-tail survey phase, MMS will observe between nine and four diffusion region events (nominal estimate of 7), and between 57 and 31 fast tailward flow events (nominal estimate of 47). Because of the restrictive nature of the criteria used to identify diffusion region events, we emphasize that the number of predicted events that we calculate represents a conservative estimate. Key Points We characterize the location and occurrence rate of nightside reconnection The occurrence rate is calculated using the Fairfield neutral sheet model The occurrence rate is used to analyze MMS predicted ephemeris ©2013. American Geophysical Union. All Rights Reserved.