Pressure Tensor Elements Breaking the Frozen-In Law During Reconnection in Earth’s Magnetotail

Egedal, J.; Ng, Jonathan; Lê, A.; Daughton, W.; Wetherton, Blake; Dorelli, J.; Gershman, D. J.; Rager, A. C.

doi:10.1103/physrevlett.123.225101

Cited by 45 publications

(62 citation statements)

References 34 publications

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“…This result was first derived in (Le et al, 2010) and has been verified in numerical studies (Le et al, 2013, 2016; Ng et al, 2011) and spacecraft observations (Egedal et al, 2019). Equation is perhaps an unexpected result as this scaling law for B H implies that the current across the EDR is set by pressure anisotropy and not by the reconnection electric field as is expected from resistive reconnection models (Parker, 1957).…”

Section: The Firehose Parameter and Anisotropy Scalingsupporting

confidence: 71%

“…The regime of low guide magnetic field B g / B rec < 0.15 is particularly important to reconnection in the Earth magnetotail. For symmetric inflow conditions, kinetic simulation studies show that this low guide field regime can be further divided into a regime of no electron jets 0.05 < B g / B rec < 0.15 and a regime B g / B rec < 0.05 with the formation of moderate length ≃30 d e electron jets (Goldman et al, 2011; Hesse et al, 2008; Karimabadi et al, 2007; Le et al, 2010; Shay et al, 2007), directly relevant to observations in the Earth's magnetotail, (Egedal et al, 2019; Torbert et al, 2018). In this letter, we extend this physics understanding to account for asymmetries in the two inflow regions setting the upstream condition for the EDRs.…”

Section: Introductionmentioning

confidence: 97%

“…The process is the source of energetic events in many types of plasmas, from tokamak disruptions in the laboratory (Wesson, 1990) to coronal mass ejections in the sun (Priest & Forbes, 2000), and may even play a role in extreme events such as gamma ray bursts in distant galaxies (Schopper et al, 1998;Zhang & Yan, 2011). A key aspect of reconnection research is centered on how the electron bulk flow decouples from the motion of the magnetic field lines within electron diffusion region (EDRs), permitting for rapid changes in the system size magnetic field line topology (Dungey, 1953). Extended EDRs with embedded electron jets have been detected in situ by spacecraft in the Earth's magnetosphere (Phan et al, 2007;Wilder et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Influence of Inflow Density and Temperature Asymmetry on the Formation of Electron Jets during Magnetic Reconnection

Montag

Egedal

Daughton

2020

Geophysical Research Letters

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The structure of the electron diffusion region (EDR), fundamental to a comprehensive theory of magnetic reconnection, is highly sensitive to asymmetry in the plasma parameters across the reconnection current layer. Using known scaling laws for the inflow region electron pressure anisotropy, a model is developed to predict the formation of extended electron jets within the EDR. Confirmed by kinetic simulation, the analysis shows how embedded electron jets are driven for scenarios fulfilling a generalized symmetry conditions based on the marginal firehose condition.

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Section: The Firehose Parameter and Anisotropy Scalingsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Influence of Inflow Density and Temperature Asymmetry on the Formation of Electron Jets during Magnetic Reconnection

Montag

Egedal

Daughton

2020

Geophysical Research Letters

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“…[2018] and Figure 2 from Egedal et al. [2019]). J. Chen (1992) and Büchner and Zelenyi (1989) detailed quasiadiabatic particle dynamics, in which particles in fields with curvature scales comparable to their gyroradii behave in a mixture of structured gyromotion (adiabatic) and chaotic scattering (nonadiabatic) depending strongly on their gyrophase.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of Energetic Electrons Near Active Magnetotail Reconnection Sites: Tracers of a Complex Magnetic Topology and Evidence of Localized Acceleration

Turner

Cohen

Bingham

et al. 2021

Geophysical Research Letters

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Magnetic reconnection is a fundamental physical process affecting plasmas from laboratory experiments to astrophysical environments (Hesse & Cassak, 2020; Zweibel & Yamada, 2009). Reconnection involves the explosive reconfiguration of magnetic field topologies, in which two previously unconnected field lines break apart and reconnect to each other. The reconnection itself takes place at very small scales, corresponding to thermal electron kinetic scales (e.g., several to ∼10 s of km in Earth's magnetosphere [Burch & Phan, 2016]), in a location referred to as the electron diffusion region (EDR) that lies at the intersection of an "X-line" in the magnetic topology (by "topology" we mean an instantaneous snapshot of the time-varying, 3-dimensional spatial configuration of magnetic field-lines). During reconnection, which is an energy conversion process in plasma physics, energy stored in the magnetic field is transferred to the particles in the plasma. That energy transfer results in kinetic motion manifested as outflow jets from the reconnection site, plasma heating, and acceleration of suprathermal energetic particles. The electron-scale physics and microscopic nature of reconnection have recently been illuminated in unprecedented detail by NASA'

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“…It is possible that magnetic tension resulting under a low reconnection rate (^A A of order 0.1 mV m ?6 ) ( Fig. 4b) was not strong enough to accelerate electrons, injected into the ECS at a high rate (equivalent to _`a,I = 1 − 2 mV m ?6 ) ( as well as other EDRs 4,9 , and earlier studies demonstrated that they can quantitatively account for the electric field ( I ) of fast reconnection as observed 16,17 . We derive a diffusion equation…”

mentioning

confidence: 77%

Magnetic-field annihilation and island formation in electron-scale current sheet in Earth's magnetotail

Hasegawa

Denton

Genestreti

et al. 2020

Preprint

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Establishing the mechanism of magnetic-to-particle energy conversion through magnetic reconnection in current sheets1 is the key to understanding the impact of fast release of magnetic energy in many space and astrophysical plasma systems, such as during magnetospheric substorms2,3. It is generally believed that an electron-scale diffusion region (EDR), where a magnetic-to-electron energy conversion occurs, has an X-type magnetic-field geometry4 around which the energy of anti-parallel magnetic fields injected is mostly converted to the bulk-flow energy of electrons by magnetic tension of reconnected field-lines5,6. However, it is at present unknown exactly how this energy conversion occurs in EDRs, because there has been no observational method to fully address this problem. Here we present state-of-the-art analysis of multi-spacecraft observations in Earth’s magnetotail of an electron-scale current sheet, which demonstrates that contrary to the standard model of reconnection with an X-type EDR geometry, the fast energy conversion in the detected EDR was caused mostly by magnetic-field annihilation, rather than reconnection. Furthermore, we detected a magnetic island forming in the EDR itself, implying that the EDR had an elongated shape ideal for island generation7 and magnetic-field annihilation. The experimental discovery of the annihilation-dominated EDR reveals a new form of energy conversion in the reconnection process that can occur when the EDR has evolved from the X-type to planar geometry.

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Pressure Tensor Elements Breaking the Frozen-In Law During Reconnection in Earth’s Magnetotail

Cited by 45 publications

References 34 publications

Influence of Inflow Density and Temperature Asymmetry on the Formation of Electron Jets during Magnetic Reconnection

Influence of Inflow Density and Temperature Asymmetry on the Formation of Electron Jets during Magnetic Reconnection

Characteristics of Energetic Electrons Near Active Magnetotail Reconnection Sites: Tracers of a Complex Magnetic Topology and Evidence of Localized Acceleration

Magnetic-field annihilation and island formation in electron-scale current sheet in Earth's magnetotail

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