Applying Magnetic Curvature to MMS Data to Identify Thin Current Sheets Relative to Tail Reconnection

Abstract

Thin current sheets (TCSs) have been postulated to be a necessary precondition for reconnection onset. Magnetic reconnection X‐lines in the magnetotail have been observed to be more common duskward of midnight. We take advantage of the MMS tetrahedral formation during the 2017–2020 MMS tail seasons to calculate the thickness of the cross‐tail neutral sheet relative to ion gyroradius. While a similar technique was applied to Cluster data, current sheet thickness over a broader range of radial distances has not been robustly explored before this study. We compare our analysis to recent theories regarding mechanisms of tail current sheet thinning and to recent simulations. We find MMS spent more than twice as long in ion‐scale TCSs in the pre‐midnight sector than post‐midnight, despite nearly even plasma sheet dwell time. The dawn‐dusk asymmetry in the distribution of Ion Diffusion Regions, as previously reported in relation to regions of TCSs, is also analyzed.

Global Structure of Magnetotail Reconnection Revealed by Mining Space Magnetometer Data

“…A recent systematic survey of MMS plasma and field data in 2017 (Rogers et al, 2019) identified 12 such magnetotail IDRs, defined as correlated reversals of the proton bulk flow velocity, v x , and the North-South magnetic field, B z , as shown in Figure 1 inset, along with additional Hall magnetic and electric field signatures. That analysis was later extended to 2018-2020 for a total of 26 IDR events (Rogers et al, 2023) labeled here A-Z, "IDR alphabet", listed in Table 2. The second column in the table lists the starting date and time of each IDR interval found in Rogers et al (2023).…”

“…That analysis was later extended to 2018-2020 for a total of 26 IDR events (Rogers et al, 2023) labeled here A-Z, "IDR alphabet", listed in Table 2. The second column in the table lists the starting date and time of each IDR interval found in Rogers et al (2023). Due to the 5 min cadence of our DM approach, the actual reconstructed times are rounded to the nearest 5 min as indicated in the third column.…”

“…The second column in the table lists the starting date and time of each IDR interval found in Rogers et al. (2023). Due to the 5 min cadence of our DM approach, the actual reconstructed times are rounded to the nearest 5 min as indicated in the third column.…”

“…The recent four‐probe Magnetospheric MultiScale (MMS) mission (Burch, Moore, et al., 2016) enabled microscopic analysis of magnetotail reconnection down to electron gyroradius scales (Torbert et al., 2018). During 4 yr of MMS observations, 26 potential X‐line encounters were found in the magnetotail (Rogers et al., 2019, 2023), where explosive reconnection causes substorms (Angelopoulos et al., 2020, 2008; Sitnov, Stephens, et al., 2019). They were detected in the form of Ion Diffusion Regions (IDRs) characterized by reversals of the North‐South component of the magnetic field, B z , and of the Sun‐Earth component of the proton bulk flow velocity, v x .…”

Three‐Dimensional Magnetic Reconnection Spreading in Current Sheets of Non‐Uniform Thickness

“…7 in Tsyganenko (1998)). Thin current sheets are more commonly found from midnight to dusk (Rogers et al., 2023). The anti‐parallel field configuration and low collisionality make it an ideal system to apply the theory.…”