Separatrix regions of magnetic reconnection at the magnetopause

Lindstedt, T.; Khotyaintsev, Yuri; Vaivads, A.; André, Mats; Fear, R. C.; Lavraud, B.; Haaland, Stein; Owen, C. J.

doi:10.5194/angeo-27-4039-2009

Cited by 31 publications

(49 citation statements)

References 53 publications

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“…The magnetic separatrix is inside the separatrix, implying that the Hall effect can extend outside of the magnetic separatrix. In addition, we will show that the enhanced D ng region along magnetic separatrix line marks the boundary of the accelerated electrons, which is consistent with the previously reported electron separatrix (e.g., Lindstedt et al 2009). …”

Section: Simulation Results and Discussionsupporting

confidence: 77%

“…The separatrix is a region where the field and plasma quantities are different from those of the inflow region and outflow region. The features and structures of the separatrix region at the magnetopause have been observed by Cluster (Khotyaintsev et al 2006;Retinò et al 2006;Lindstedt et al 2009). These observations mainly recorded the magnetospheric branch of the separatrix region at tens of d i (ion inertial length) away from the X-line.…”

Section: Introductionmentioning

confidence: 89%

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Current structure and flow pattern on the electron separatrix in reconnection region

Guo

Wei

2017

Geosci. Lett.

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Results from 2.5D Particle-in-cell (PIC) simulations of symmetric reconnection with negligible guide field reveal that the accessible boundary of the electrons accelerated in the magnetic reconnection region is displayed by enhanced electron nongyrotropy downstream from the X-line. The boundary, hereafter termed the electron separatrix, occurs at a few d e (electron inertial length) away from the exhaust side of the magnetic separatrix. On the inflow side of the electron separatrix, the current is mainly carried by parallel accelerated electrons, served as the inflow region patch of the Hall current. The out-of-plane current density enhances at the electron separatrix. The dominating current carriers are the electrons, nongyrotropic distribution functions of which contribute significantly to the perpendicular electron velocity by increasing the electron diamagnetic drift velocity. When crossing the separatrix region where the Hall electric field is enhanced, electron velocity orientation is changed dramatically, which could be a diagnostic indicator to detect the electron separatrix. In the exhaust region, ions are the main carriers for the out-of-plane current, while the parallel current is still mainly carried by electrons. The current density peak in the separatrix region implies that a thin current sheet is formed apart from the neutral line, which can evolve to the bifurcated current sheet.

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Section: Simulation Results and Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 89%

Current structure and flow pattern on the electron separatrix in reconnection region

Guo

Wei

2017

Geosci. Lett.

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“…This suggests that the MSP separatrix, i.e., the field line connected to the X line, must be located at the MSP edge of the electron CS, which implies that we observe intrusion of both the MSH ions and electrons into the MSP inflow region. Such intrusion is an indication of close proximity to the X line and is not observed at larger distances [ Lindstedt et al , ]. The intruding electrons can be caused by a scattering/diffusion process related to turbulence [ Vaivads et al , ] or magnetic field curvature [ Lavraud et al , ].…”

Section: Observationsmentioning

confidence: 99%

Electron jet of asymmetric reconnection

Khotyaintsev

Graham

Norgren

et al. 2016

Geophysical Research Letters

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We present Magnetospheric Multiscale observations of an electron‐scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E∥ amplitudes reaching up to 300 mV m−1 and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron‐ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron‐scale physics of asymmetric reconnection.

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“…The peak velocity of the jet is ∼350 km/s. The ion edge, i.e., first observation of sheath ions, occurs at 18:53:21 UTC and corresponds to the transition between the separatrix region and the outflow region [Lindstedt et al, 2009]. The black curve indicates the resulting energy of the E × B ion drift.…”

Section: Cold Ions At the Magnetopausementioning

confidence: 99%

Cold ion heating at the dayside magnetopause during magnetic reconnection

Toledo‐Redondo

André

Vaivads

et al. 2016

Geophysical Research Letters

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Cold ions of ionospheric origin are known to be present in the magnetospheric side of the Earth's magnetopause. They can be very abundant, with densities up to 100 cm−3. These cold ions can mass load the magnetosphere, changing global parameters of magnetic reconnection, like the Alfvén speed or the reconnection rate. In addition they introduce a new length scale related to their gyroradius and kinetic effects which must be accounted for. We report in situ observations of cold ion heating in the separatrix owing to time and space fluctuations of the electric field. When this occurs, the cold ions are preheated before crossing the Hall electric field barrier. However, when this mechanism is not present cold ions can be observed well inside the reconnection exhaust. Our observations suggest that the perpendicular cold ion heating is stronger close to the X line owing to waves and electric field gradients linked to the reconnection process.

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Separatrix regions of magnetic reconnection at the magnetopause

Cited by 31 publications

References 53 publications

Current structure and flow pattern on the electron separatrix in reconnection region

Current structure and flow pattern on the electron separatrix in reconnection region

Electron jet of asymmetric reconnection

Cold ion heating at the dayside magnetopause during magnetic reconnection

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