On the Occurrence of Magnetic Reconnection Along the Terrestrial Magnetopause, Using Magnetospheric Multiscale (MMS) Observations in Proximity to the Reconnection Site

Abstract

Observations at the reconnection site from the Magnetospheric Multiscale mission are used to examine the occurrence of magnetic reconnection along the magnetopause in relation to both the upstream interplanetary magnetic field (IMF) orientation and local magnetosheath variations. While there is a statistically larger number of reconnection intervals observed downstream of the quasi‐parallel bow shock than is accounted for based on the histogram of overall IMF orientations, it is surmised that increased fluctuations downstream of the quasi‐parallel bow shock cause greater large‐scale motion of the magnetopause surface; but do not preferentially enhance the occurrence of steady magnetic reconnection. An examination of the locations of observed reconnection sites relative to model predictions also suggest that enhanced magnetosheath fluctuations do not result in steady reconnection occurring at random locations at the magnetopause.

Statistical Comparison of Various Dayside Magnetopause Reconnection X‐Line Prediction Models

“…If there are multiple instances of |ΔV L | > 70 km/s within the 10 min period, then the interval which has the highest peak of ΔV L is checked for the presence of a jet. The methodology to identify jet reversals is based on the methodology developed by Trattner, Burch, et al (2017) and used in previous statistical studies (Petrinec et al, 2022;Trattner, Burch, et al, 2017).…”

“…This enhancement, known as a reconnection jet, is an indication that reconnection is occurring nearby. Enhanced ion velocities with switching directions are called jet reversals, and are evidence of an X‐line nearby the spacecraft position (e.g., Cowley, 1982; Dunlop et al., 2011; Gosling et al., 1982; Paschmann et al., 1979; Petrinec et al., 2022; Pu et al., 2007; Trattner, Burch, et al., 2017).…”

“…In order to identify jet‐reversal, we look for switches in Δ V L by more than ±70 km/s within a 2‐min window of the 10‐min time series data. Previous studies (Petrinec et al., 2022; Trattner, Burch, et al., 2017) have used the same velocity change and time window values for a similar data set. This study adds additional conditions to the crossings in order to constrain uncertain crossing measurements.…”

“…The methodology to identify jet reversals is based on the methodology developed by Trattner, Burch, et al. (2017) and used in previous statistical studies (Petrinec et al., 2022; Trattner, Burch, et al., 2017).…”

Tracking Magnetopause Motion Using Cold Plasmaspheric Ions

“…Tests using over 300 MMS magnetopause crossings early in the mission showed that the model predicted the location of the reconnection X‐line within ±1 R E with approximately 85% accuracy (Petrinec et al., 2016; Trattner et al., 2017a, 2017b; Trattner, Fuselier, et al., 2021; Trattner, Petrinec, & Fuselier, 2021). This model is valid even for MP motion not associated with the erosion of the magnetopause by reconnection; such as motion due to changes in the dynamic pressure, fluctuations downstream of the quasi‐parallel bow shock, and rotations in clock angle (Fuselier et al., 2023; Petrinec et al., 2022; Russell et al., 1997).…”