The physical foundation of the reconnection electric field

Hesse, M.; Liu, Y.-H.; Chen, Li‐Jen; Bessho, Naoki; Wang, S.; Burch, J. L.; Moretto, T.; Norgren, Cecilia; Genestreti, K. J.; Phan, T. D.; Tenfjord, P.

doi:10.1063/1.5021461

Cited by 23 publications

(31 citation statements)

References 21 publications

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“…As is evident, both terms seem to play some role in governing the energy conversion rate near the X‐point. At the exact X‐point, which we have suggested to have been northward of MMS, it is expected that the agyrotropic pressure force dominates the gyrotropic force completely, whereas the opposite is expected outside the EDR (Hesse et al, ). In the strong positive peak of

\overset{J}{true} \cdot {\overset{E}{true}}^{'}

, the gyrotropic term is roughly half as large as the agyrotropic term.…”

Section: Energy Conversion Near Bl Reversalmentioning

confidence: 82%

MMS Observation of Asymmetric Reconnection Supported by 3‐D Electron Pressure Divergence

et al. 2018

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We identify the electron diffusion region (EDR) of a guide field dayside reconnection site encountered by the Magnetospheric Multiscale (MMS) mission and estimate the terms in generalized Ohm's law that controlled energy conversion near the X‐point. MMS crossed the moderate‐shear (∼130°) magnetopause southward of the exact X‐point. MMS likely entered the magnetopause far from the X‐point, outside the EDR, as the size of the reconnection layer was less than but comparable to the magnetosheath proton gyroradius, and also as anisotropic gyrotropic “outflow” crescent electron distributions were observed. MMS then approached the X‐point, where all four spacecraft simultaneously observed signatures of the EDR, for example, an intense out‐of‐plane electron current, moderate electron agyrotropy, intense electron anisotropy, nonideal electric fields, and nonideal energy conversion. We find that the electric field associated with the nonideal energy conversion is (a) well described by the sum of the electron inertial and pressure divergence terms in generalized Ohms law though (b) the pressure divergence term dominates the inertial term by roughly a factor of 5:1, (c) both the gyrotropic and agyrotropic pressure forces contribute to energy conversion at the X‐point, and (d) both out‐of‐the‐reconnection‐plane gradients (∂/∂M) and in‐plane (∂/∂L,N) in the pressure tensor contribute to energy conversion near the X‐point. This indicates that this EDR had some electron‐scale structure in the out‐of‐plane direction during the time when (and at the location where) the reconnection site was observed.

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\overset{J}{true} \cdot {\overset{E}{true}}^{'}

, the gyrotropic term is roughly half as large as the agyrotropic term.…”

Section: Energy Conversion Near Bl Reversalmentioning

confidence: 82%

MMS Observation of Asymmetric Reconnection Supported by 3‐D Electron Pressure Divergence

et al. 2018

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“…The separation of ions and electrons also results in strong Hall currents in the decoupling (or diffusion) regions. Panel (ix) shows MMS1 and MMS2 observations of a negative enhancement in

E_{M}^{'}

, which is often referred as the reconnection electric field in many reconnection studies (e.g., Hesse et al, ) and is expected to be the strongest in the electron diffusion region. Panels (x)–(xii) show the N , M , and L components of current density J = en e ( V i − V e ) computed using plasma moments from FPI's plasma distribution functions.…”

Section: Fields and Plasma Signatures Of Re‐reconnection X‐linementioning

confidence: 99%

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Poh

Slavin

et al. 2019

JGR Space Physics

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Three‐dimensional global hybrid simulations and observations have shown that earthward‐moving flux ropes (FRs) can undergo magnetic reconnection (or re‐reconnection) with the near‐Earth dipole field to create dipolarization front (DF)‐like signatures that are immediately preceded by brief intervals of negative BZ. The simultaneous erosion of the southward BZ field at the leading edge of the FR and continuous reconnection of lobe magnetic flux at the X‐line tailward of the FR result in the asymmetric south‐north BZ signature in many earthward‐moving FRs and possibly DFs with negative BZ dips prior to their observation. In this study, we analyzed Magnetospheric MultiScale (MMS) observation of fields and plasma signatures associated with the encounter of an ion diffusion region ahead of an earthward‐moving FR on 3 August 2017. The signatures of this re‐reconnection event were (i) +/− BZ reversal, (ii) −/+ bipolar‐type quadrupolar Hall magnetic fields, (iii) northward super‐Alfvénic electron outflow jet of ~1,000–1,500 km/s, (iv) Hall electric field of ~15 mV/m, (v) intense currents of ~40–100 nA/m2, and (vi) J·E′ ~0.11 nW/m3. Our analysis suggests that the MMS spacecraft encounters the ion and electron diffusion regions but misses the X‐line. Our results are in good agreement with particle‐in‐cell simulations of Lu et al. (2016, https://doi.org/10.1002/2016JA022815). We computed a dimensionless reconnection rate of ~0.09 for this re‐reconnection event and through modeling, estimating that the FR would fully dissipate by −16.58 RE. We demonstrated pertubations in the high‐latitude ionospheric currents at the same time of the dissipation of earthward‐moving FRs using ground‐ and space‐based measurements.

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“…How the collisionless plasma in the magnetotail breaks the frozen-in condition to enable reconnection is a fundamental question that has received intense attention. Particle-in-cell (PIC) simulations (e.g., Bessho et al, 2014;Chen et al, 2011;Hesse et al, 2018;Ishizawa et al, 2004;Ng et al, 2011;Shuster et al, 2015), in particular, predict that meandering dominates the electron dynamics in the X-line region. Particle-in-cell (PIC) simulations (e.g., Bessho et al, 2014;Chen et al, 2011;Hesse et al, 2018;Ishizawa et al, 2004;Ng et al, 2011;Shuster et al, 2015), in particular, predict that meandering dominates the electron dynamics in the X-line region.…”

Section: Introductionmentioning

confidence: 99%

“…For reconnection with zero guide magnetic field along the electric current, electron meandering-bouncing of demagnetized electrons at the field reversals of the current sheet (e.g., Speiser, 1965)-has been recognized to be central to breaking the frozen in condition [see, e.g., the review paper by Hesse et al, 2011]. Particle-in-cell (PIC) simulations (e.g., Bessho et al, 2014;Chen et al, 2011;Hesse et al, 2018;Ishizawa et al, 2004;Ng et al, 2011;Shuster et al, 2015), in particular, predict that meandering dominates the electron dynamics in the X-line region. ©2019.…”

Section: Introductionmentioning

confidence: 99%

Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields

Chen

Wang

Hesse

et al. 2019

Geophysical Research Letters

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Kinetic structures of electron diffusion regions (EDRs) under finite guide fields in magnetotail reconnection are reported. The EDRs with guide fields 0.14–0.5 (in unit of the reconnecting component) are detected by the Magnetospheric Multiscale spacecraft. The key new features include the following: (1) cold inflowing electrons accelerated along the guide field and demagnetized at the magnetic field minimum while remaining a coherent population with a low perpendicular temperature, (2) wave fluctuations generating strong perpendicular electron flows followed by alternating parallel flows inside the reconnecting current sheet under an intermediate guide field, and (3) gyrophase bunched electrons with high parallel speeds leaving the X‐line region. The normalized reconnection rates for the three EDRs range from 0.05 to 0.3. The measurements reveal that finite guide fields introduce new mechanisms to break the electron frozen‐in condition.

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The physical foundation of the reconnection electric field

Cited by 23 publications

References 21 publications

MMS Observation of Asymmetric Reconnection Supported by 3‐D Electron Pressure Divergence

MMS Observation of Asymmetric Reconnection Supported by 3‐D Electron Pressure Divergence

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields

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