Asymmetric Reconnection Within a Flux Rope‐Type Dipolarization Front

Marshall, A.; Burch, J. L.; Reiff, P. H.; Webster, J.; Torbert, R. B.; Ergun, R. E.; Russell, C. T.; Strangeway, R. J.; Giles, B. L.; Nakamura, R.; Hwang, K-J; Genestreti, K. J.

doi:10.1029/2019ja027296

Cited by 7 publications

(18 citation statements)

References 55 publications

(105 reference statements)

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“…We note that the strong variations of the B z field seen in Figure 9a made applying the LMN coordinate system to Event 3 difficult. This is because the L component in LMN would be close to the x direction in GSM, as seen in earlier studies (Marshall et al., 2020 ). This might suggest the filamentation of the original tail current sheet and even its strong bending, which would distort the global picture for this WS predicted by DM reconstruction (Figure 8 ).…”

Section: Observationssupporting

confidence: 69%

A New Perspective on Magnetotail Electron and Ion Divergent Flows: MMS Observations

et al. 2022

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Magnetic reconnection is a key process in collisionless plasmas that converts magnetic energy into plasma kinetic and thermal energies through a rapid change of magnetic field topology. At the Earth's magnetopause, the reconnection process leads to efficient transport of solar wind energy into the magnetosphere, whereas in the magnetotail, it explosively releases the accumulated magnetic energy and causes global geomagnetic disturbances leading to auroral substorms (Baker et al., 1996;Hones, 1984). The energy conversion and topological changes take place in a very small region surrounding an X-line where ions or both ions and electrons are decoupled from the magnetic field. These regions are called the diffusion regions. They have a multiscale structure due to different masses and hence dynamics of ions and electrons. A larger ion diffusion region (IDR) with unmagnetized ions usually contains a smaller-scale electron diffusion region (EDR) where both electrons and ions are unmagnetized.A distinctive feature of the magnetotail reconnection onset is that corresponding plasma motions are needed to reduce the original finite normal magnetic field for the formation of an X-line. This is not necessary in case of antiparallel or sheared magnetic field configurations, such as at the magnetopause. Indeed, there is some controversy regarding whether fast plasma divergent flows in the magnetotail are a consequence or a cause of the magnetic topology change. In the former and the most commonly accepted scenario, the magnetic topology first changes because of the slow evolution of the tail induced by the external driving and subsequent microscale tearing instability (e.g., Liu et al., 2014). Therefore, plasma divergent flows arise from the unbalanced magnetic tension of the sharply kinked, newly reconnected field lines around the X-line.The latter scenario was originally proposed by Lin and Swift (2002). On the basis of the analysis of their 2-D global hybrid simulations, they conjectured that the magnetic topology change can be internally driven by the spontaneous generation of plasma divergent flows. The idea of such flows preceding and likely driving the reconnection onset was later elaborated on by Siscoe et al. (2009) andTanaka et al. (2019) in the analysis of their magnetohydrodynamic (MHD) simulations. These plasma divergent flows are referred to below as plasma "watersheds" (WSs), to distinguish them from reconnection ejecta emanated from an already formed X-line. Most recently, Sitnov, Motoba, and Swisdak (2021), using fully kinetic 3-D particle-in-cell (PIC) simulations,

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Section: Observationssupporting

confidence: 69%

A New Perspective on Magnetotail Electron and Ion Divergent Flows: MMS Observations

et al. 2022

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“…Journal of Geophysical Research: Space Physics electron diffusion region near the center of it (Marshall et al, 2020). J Á E increases to 0.89 nW/m 3 as J y and E y climb to their local maximum and remains positive until after B z drop from its maximum (Figure 2m).…”

Section: 1029/2020ja028568mentioning

confidence: 97%

“…Simultaneously, the intensification of current in the Y and −Z directions can be clearly seen during the DF interval (Figure 2k). This case has been studied in detail and indeed defined as a FR‐type DF with an electron diffusion region near the center of it (Marshall et al, 2020). J ⋅ E increases to 0.89 nW/m 3 as J y and E y climb to their local maximum and remains positive until after B z drop from its maximum (Figure 2m).…”

Section: Case Studymentioning

confidence: 99%

Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

et al. 2020

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Dipolarization front (DF) is an important region involved with energy conversion and flux transport in the planet's magnetotail. Using observation data from the recent Magnetospheric Multiscale (MMS) mission, we have identified and analyzed 215 DF events. Significant magnetic energy conversion and transport are observed at the DFs, which show strong dawn-dusk asymmetry. We find that the transport process dominates the change of local magnetic energy. Nearly 70% of the events show net Poynting flux flowing into the DF region. Such effect is more significant than local magnetic energy dissipation, averagely. When DF approaches the near-Earth region, the net flow-in Poynting flux decreases and magnetic energy dissipation increases. Our results suggest that the downstream magnetic energies of transient magnetic reconnections in the midtail may be transported to the near-Earth region by one DF event after another. These intensive strikes to the magnetosphere in the near-planet region may drive stronger storms, compared with the previous knowledge about DF. Plain Language Summary Dipolarization front (DF), a sharp boundary with a scale of ion inertial length, is frequently observed at the nightside of the terrestrial magnetosphere. It is widely believed that DF plays a key role in magnetic flux transport and energy conversion in the magnetotail. Reliable data from Magnetospheric Multiscale (MMS) give us an opportunity to investigate the magnetic energy conversion and transport associated with DF. We have statistically studied 215 DF events and found that the magnetic dissipation increases when DF moves toward the near-Earth region. It is interesting that the change of local magnetic energy mainly results from the net inflow Poynting flux, which is much larger than the magnetic energy dissipation in the midtail. These results suggest that DF has a long lifetime during the transport in the magnetotail and might produce a more intense impact on the inner magnetosphere and ionosphere.

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“…The LMN unit vectors, specified in the Geocentric Solar Ecliptic (GSE) coordinate system, have the following components: e L = [−0.11648, +0.27887, +0.95324], e M = [+0.07826, +0.95936, −0.27110], and e N = [−0.99010, +0.04302, −0.13357]. This LMN coordinate system is nearly the same as the one that was determined by Marshall et al (2020), differing from the latter mainly by the opposite signs of the M and N orts. The normal component of the structure velocity was determined by the timing method (Russell et al, 1983), and two other components were estimated as the average ion velocity within the 1.5 s reconstruction interval 14.51.30.25-14.51.31.75 UT.…”

Section: Steady Statementioning

confidence: 92%

“…The reconstruction of Korovinskiy et al (2021) has also revealed the signatures of CS time dependence, observed during the first 0.4 s, when the out-of-plane component E y demonstrated some reduction and the function V ey (A) was not single-valued (see Figures 2A, 3E of the cited paper), which resulted in a low reconstruction accuracy within this interval (see Figure 6 of Korovinskiy et al (2021) or Figure 3). To investigate the model failure in an unsteady CS, we addressed the event of September 8, 2018, when at nearly 14:51:30 UT, MMS encountered an EDR near the center of a flux-rope type dipolarization front (Marshall et al, 2020). The reconstruction is performed in the co-moving LMN reference frame.…”

Section: Steady Statementioning

confidence: 99%

Electron magnetohydrodynamics Grad–Shafranov reconstruction of the magnetic reconnection electron diffusion region

Korovinskiy

Panov

Nakamura

et al. 2023

Front. Astron. Space Sci.

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We present a study of the electron magnetohydrodynamics Grad–Shafranov (GS) reconstruction of the electron diffusion region (EDR) of magnetic reconnection. Two-dimensionality of the magnetoplasma configuration and steady state are the two basic assumptions of the GS reconstruction technique, which represent the method’s fundamental limitations. The present study demonstrates that the GS reconstruction can provide physically meaningful results even when these two assumptions, which are hardly fulfilled in spacecraft observations, are violated. This conclusion is supported by the reconstruction of magnetic configurations of two EDRs, encountered by the Magnetospheric Multiscale (MMS) Mission on July 11, 2017 and September 8, 2018. Here, the former event exhibited a violation of two-dimensionality, and the latter event exhibited a violation of steady state. In both cases, despite the deviations from the ideal model configuration, reasonable reconstruction results are obtained by implementing the herein introduced compressible GS reconstruction model. In addition to the discussed fundamental limitations, all existing versions of the GS reconstruction technique rely on a number of minor simplifying assumptions, which restrict the model scope and efficiency. We study the prospects for further model improvement and generalization analytically. Our analysis reveals that nearly all these minor limitations can be overcome by using a polynomial MMS-tailored reconstruction technique in the space of rotationally invariant variables instead of Cartesian coordinates.

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Asymmetric Reconnection Within a Flux Rope‐Type Dipolarization Front

Cited by 7 publications

References 55 publications

A New Perspective on Magnetotail Electron and Ion Divergent Flows: MMS Observations

A New Perspective on Magnetotail Electron and Ion Divergent Flows: MMS Observations

Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

Electron magnetohydrodynamics Grad–Shafranov reconstruction of the magnetic reconnection electron diffusion region

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