Generation of a Strong Parallel Electric Field and Embedded Electron Jet in the Exhaust of Moderate Guide Field Reconnection

Wetherton, Blake; Egedal, J.; Lê, A.; Daughton, W.

doi:10.1029/2022gl098907

Cited by 4 publications

(5 citation statements)

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“…A final remark is that while the present EMHD reconstruction assumes isotropy of the gyrotropic part of electron velocity distributions (Hasegawa et al., 2021 ), strong electron temperature anisotropy is common in reconnection layers (Figures 1e and 8e ), in particular, in the presence of guide field (e.g., Wetherton et al., 2022 ). Further improvement of the EMHD method is thus necessary to incorporate electron pressure anisotropy effects.…”

Section: Discussionmentioning

confidence: 88%

Ion‐Scale Magnetic Flux Rope Generated From Electron‐Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

et al. 2023

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Magnetopause (MP) reconnection often occurs in a time-dependent and/or localized manner, generating flux transfer events (FTEs). FTEs are characterized by a bipolar variation of the magnetic field component normal to the nominal MP and also generally by an enhancement of the field magnitude around the event center (see Raeder (2006) and Hasegawa (2012) for reviews). While large-scale FTEs (typically with dimensions ∼1 𝐴𝐴 RE ) have been extensively investigated both theoretically and observationally and their formation processes are relatively

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Section: Discussionmentioning

confidence: 88%

Ion‐Scale Magnetic Flux Rope Generated From Electron‐Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

et al. 2023

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“…Then the question comes to why there is a large E ‖ in guide-field reconnection. In a kinetic simulation of reconnection with a moderate guide-field, a large E ‖ , which is cocurrent with the electron current sheet, is generated to balance the parallel electron pressure gradient of the two electron populations across this current sheet: one is relatively isotropic, and the other is anisotropic (Wetherton et al, 2022). In the moderate guide-field reconnection (the normalized guide field is ∼0.5), the electron firehose condition is marginally approached, responsible for the unmagnetized isotropic electron population.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…First, we assume E ‖ is mostly in the M-N plane to get the checked relation above, but E ‖ is not always in this plane from observations (Wilder et al, 2018). Second, the full pressure tensor effects are not included (Wetherton et al, 2022).…”

Section: Discussion and Summarymentioning

confidence: 99%

“…This large E ‖ is balanced by the electron pressure gradient in an MMS event study (Wilder et al, 2017). As revealed from a kinetic simulation of moderate guide field reconnection, E ‖ is suggested to be balanced by the parallel electron pressure gradient caused by a transition between isotropic and anisotropic electrons at the two sides of the electron jet (Wetherton et al, 2022). However, the generation of this E ‖ in strong guide-field reconnection is still not fully understood.…”

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confidence: 98%

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Electron Dynamics in the Electron Current Sheet During Strong Guide‐Field Reconnection

Wang

Tang

et al. 2023

Geophysical Research Letters

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Magnetic reconnection is a fundamental process with explosive energy conversion from magnetic fields to plasmas and rapid reconfiguration of magnetic field lines. In general, the reconnecting magnetic fields do not have to be antiparallel, and an additional magnetic component known as the guide field (B g ) can appear in the direction perpendicular to the reconnecting plane. With the increase of B g , the guide field can gradually magnetize electrons in the central diffusion region (e.g., Le et al., 2013), resulting into the transition from antiparallel to guide-field reconnection (Swisdak et al., 2005). In guide-field reconnection, B g can cause the diamagnetic drift of the X-line, which may eventually suppress reconnection (e.g., Phan et al., 2013;Swisdak et al., 2003). The reconnection current sheet is deflected by the J L × B g force (J L is the current along the reconnecting direction, Goldman et al., 2011;Tang et al., 2022), and the Hall field structure is accordingly distorted (Eastwood et al., 2010). The reconnection electric field becomes parallel to the guide field in the vicinity of the X-line, which leads to the shift of the local energy conversion location to the magnetic field reversal points (Genestreti et al., 2017) and the significance of parallel energy dissipation (Wilder et al., 2018). In addition, this parallel electric field (E ‖ ) can accelerate electrons from one direction, and decelerate electrons from the other direction, forming a density cavity on one edge of the exhaust (Eastwood et al., 2018) and electron beams that are unstable for electron beamtype instabilities (e.g.,

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“…A final remark is that while the present EMHD reconstruction assumes isotropy of the gyrotropic part of electron velocity distributions (Hasegawa et al, 2021), strong electron temperature anisotropy is common in reconnection layers (Figures 1e and 7e), in particular, in the presence of guide field (e.g., Wetherton et al, 2022). Further improvement of the EMHD method is thus necessary to incorporate electron pressure anisotropy effects.…”

Section: The Last Point Implies That While Significant J • Ementioning

confidence: 94%

Three-Dimensional Ion-Scale Magnetic Flux Rope Generated from Electron-Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

Hasegawa

Denton

Dokgo

et al. 2022

Preprint

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We present in-depth analysis of three southward-moving meso-scale (ion-to magnetohydrodynamic-scale) flux transfer events (FTEs) and subsequent crossing of a reconnecting electron-scale current sheet (ECS), which were observed on 8 December 2015 by the Magnetospheric Multiscale spacecraft near the subsolar magnetopause under southward and duskward magnetosheath magnetic field conditions. Our aims are to understand the generation mechanism of ion-scale magnetic flux ropes (ISFRs) and to reveal causal relationship among magnetic structures of the ECS, electromagnetic energy conversion, and kinetic processes in magnetic reconnection layers. Magnetic field reconstruction methods show that a flux rope with a length of about one ion inertial length existed and was growing in the ECS, supporting the idea that ISFRs can be generated from secondary magnetic reconnection in ECS. Grad-Shafranov reconstruction applied to the three FTEs shows that the FTE flux ropes had axial orientations similar to that of the ISFR in the ECS. This suggests that these FTEs also formed through the same secondary reconnection process, rather than multiple X-line reconnection at spatially separated locations. Four-spacecraft observations of electron pitch-angle distributions and energy conversion rate suggest that the ISFR had three-dimensional magnetic topology and secondary reconnection was patchy or bursty. Previously reported positive and negative values of , with magnitudes much larger than expected for typical magnetopause reconnection, were seen in both magnetosheath and magnetospheric separatrix regions of the ISFR. Many of them coexisted with bi-directional electron beams and intense electric field fluctuations around the electron gyrofrequency, consistent with their origin in separatrix activities.

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Generation of a Strong Parallel Electric Field and Embedded Electron Jet in the Exhaust of Moderate Guide Field Reconnection

Cited by 4 publications

References 39 publications

Ion‐Scale Magnetic Flux Rope Generated From Electron‐Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

Ion‐Scale Magnetic Flux Rope Generated From Electron‐Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

Electron Dynamics in the Electron Current Sheet During Strong Guide‐Field Reconnection

Three-Dimensional Ion-Scale Magnetic Flux Rope Generated from Electron-Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations

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