MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub‐Alfvénic Flow

Farrugia, C. J.; Lugaz, Noé; Alm, L.; Vasquez, Bernard J.; Argall, M. R.; Kucharek, H.; Matsui, H.; Torbert, R. B.; Lavraud, B.; Contel, O. Le; Cohen, I. J.; Burch, J. L.; Russell, C. T.; Strangeway, R. J.; Shuster, J. R.; Dorelli, J.; Eastwood, J. P.; Ergun, R. E.; Fuselier, S. A.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Yuri V.; Lindqvist, Per‐Arne; Marklund, Göran; Paulson, K. W.; Petrinec, S. M.; Phan, T. D.; Pollock, C. J.

doi:10.1002/2017ja024563

Cited by 3 publications

(11 citation statements)

References 33 publications

(53 reference statements)

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“…These results are consistent with those reported by Farrugia et al. (2017) for this crossing. However, even for the full time interval in the figure, there is no sign reversal of the correlation between

\vec{B}

and

\vec{V}

.…”

Section: Observationssupporting

confidence: 94%

“…It occurred in an approximate GSE longitude range, from −50 E  during the outward magnetopause crossing to −8 E  during the inward crossing some 10 h later. A portion of the event has been previously examined by Farrugia et al (2017). The present paper provides an overview of the total events and a discussion of possible origins of what we refer to as the "Anomalous Reconnection Layer" (ARL).…”

Section: Summary Of Observationsmentioning

confidence: 99%

“…The prior study by Farrugia et al. (2017) was focused on the subinterval 00:00–03:00 UT on 01 January, which contains two transitions between the magnetosheath proper and what they refer to as the magnetosphere. On account of its unusual magnetic field direction and other properties, we have chosen to instead identify this region as a distinct layer, the ARL, sandwiched between the magnetosheath proper and the magnetopause proper.…”

Section: Observationsmentioning

confidence: 99%

“…A portion of the overall event has already been examined in detail by Farrugia et al. (2017). These authors interpreted the event in terms of multiple crossings of the magnetopause.…”

Section: Introductionmentioning

confidence: 99%

“…Crossings 3 and 4 were identified by Farrugia et al (2017) as possible passes of MMS through the ion diffusion region associated with a nearby reconnection site. Detailed analysis of these two crossings can be found in their paper, in which our ARL is referred to as the magnetosphere.…”

mentioning

confidence: 99%

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Anomalous Reconnection Layer at Earth's Dayside Magnetopause

et al. 2021

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Observations by the Magnetospheric Multiscale spacecraft (MMS) of an unusual layer, located between the dayside magnetosheath and the magnetosphere, alternating with encounters with the magnetosheath during an extended time period between December 31, 2015 and January 01, 2016, when the interplanetary magnetic field was strongly southward and the Earth's dipole tilt large and negative, are presented. It appears to have been magnetically connected to both magnetosphere and magnetosheath. The layer appears to be located mostly on closed field lines and was bounded by a rotational discontinuity (RD) at its magnetosheath edge and by the magnetosphere on its earthward side. A separatrix layer, with heated magnetosheath electrons streaming unidirectionally along the field lines, was present sunward of the RD. We infer that the layer was started by a dominant reconnection site well north of the spacecraft and that it may have gained additional width, from a large drop in solar wind density and ram pressure, which preceded the beginning of the event by more than an hour. Relative to the magnetosheath, in which the magnetic field was strongly southward, this unusual layer was characterized by a less southward, more dawnward magnetic field of lower magnitude. The plasma density and flow speed in the region were lower than in the magnetosheath, albeit with Alfvénic jetting occurring at the magnetosheath edge as well as at the magnetospheric edge of the layer. The closing of the magnetic field lines requires the existence of another reconnection site, located southward/tailward of MMS.

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\vec{B}

and

\vec{V}

.…”

Section: Observationssupporting

confidence: 94%

Section: Summary Of Observationsmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

“…A portion of the overall event has already been examined in detail by Farrugia et al. (2017). These authors interpreted the event in terms of multiple crossings of the magnetopause.…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Anomalous Reconnection Layer at Earth's Dayside Magnetopause

et al. 2021

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MMS Observations of Storm‐Time Magnetopause Boundary Layers in the Vicinity of the Southern Cusp

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Chen

Fuselier

et al. 2022

Geophysical Research Letters

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For southward interplanetary magnetic field (IMF), day-side reconnection produces a low-latitude magnetopause BL composed of newly reconnected magnetic flux. On the magnetosheath side, the magnetosheath boundary layer (MSBL) contains both magnetosphere and magnetosheath plasma (Cowley, 1982;Eastman & Hones, 1979;Mitchell et al., 1987). At the low-shear magnetopause, electrons above 50 eV can be used as an indicator of the transition from magnetosheath to MSBL, due to the changing topological connection (Fuselier et al., 1997). The low-latitude boundary layer (LLBL; Nakamura, 2021), composed of magnetospheric reconnected field lines, is where the solar wind plasma penetrates Earth's magnetosphere. The purpose of this study is to illuminate the physics of these boundaries layers during geomagnetic storms.Typically, geomagnetically disturbed periods are characterized by enhanced entry of plasma, stronger convection, and more magnetospheric transport. Although, less is known about the magnetopause BLs during strong disturbances, since the number of useful observations is limited by the frequency of storms, occurring at about 20/year (Reyes et al., 2021). For a moderate storm, Sonnerup (1971) reported an Explorer-12 crossing of both the MSBL and LLBL, providing early evidence for the open magnetosphere model. Maynard et al. (1991) studied BL dynamics during a storm based on multi-spacecraft observations and concluded that the x-line extended over a significant range of local time, allowing the magnetosheath plasma access into the magnetosphere over this range.

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Storm‐Time Magnetopause: Pressure Balance

et al. 2022

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The magnetopause (MP) is a thin current sheet which separates shocked solar wind (SW) flow carrying frozen-in interplanetary magnetic field (IMF) from the area controlled by the terrestrial magnetic field forming the Earth's magnetosphere. The MP shape and position are determined by the upstream conditions characterized by the dynamic pressure (P DYN ) and by IMF orientation, mostly represented by its B Z component. When approaching the Earth magnetosphere, the supersonic SW is converted into a subsonic plasma flow through a formation of the bow shock. The region between the bow shock and MP, so called the magnetosheath, is occupied by the SW plasma that is slowed down, heated, and compressed and its dynamic pressure is converted into the thermal (ion plus electron) and magnetic pressures. The sum of the pressures is expected to be nearly equal to the SW dynamic pressure (note that farther from the subsolar point, the magnetosheath velocity is non-zero). However, Samsonov et al. (2012) andSamsonov et al. (2016) reported that the total pressure exerted onto the subsolar MP is lower than the SW dynamic pressure and their ratio depends on the IMF orientation. Thus, the MP location is given by a balance of the magnetosheath total pressure and magnetospheric magnetic pressure because the pressure of hot and tenuous magnetospheric plasma is supposed to be negligible. This approach is used in many MP empirical models because it leads to scaling of the MP standoff distance as 𝐴𝐴 𝐴𝐴 −1∕6 DYN . Based on this simple consideration, the magnitude of the magnetospheric magnetic field (B MSP ) would be larger than that in the magnetosheath (B MSH ). However, Farrugia et al. (2017) presented the observations of two dayside MP crossings when B MSH is by a factor of 2.2 larger than B MSP during a passage of the magnetic cloud when IMF was high, the upstream dynamic pressure dropped notably under 1 nPa and the SW flow became sub-Alfvénic. Although these circumstances in the SW are exceptional, the interaction of a low Mach number (M A

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MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub‐Alfvénic Flow

Cited by 3 publications

References 33 publications

Anomalous Reconnection Layer at Earth's Dayside Magnetopause

Anomalous Reconnection Layer at Earth's Dayside Magnetopause

MMS Observations of Storm‐Time Magnetopause Boundary Layers in the Vicinity of the Southern Cusp

Storm‐Time Magnetopause: Pressure Balance

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