Electromagnetic hybrid‐code simulation of magnetic reconnection: Velocity distribution functions of accelerated ions

Nakabayashi, J.; Machida, S.

doi:10.1029/97gl01206

Cited by 21 publications

(11 citation statements)

References 9 publications

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“… 2014 ). The latter was noticed earlier in hybrid and PIC simulations (Nakabayashi and Machida 1997 ; Zenitani et al. 2013 ), where it was interpreted as a pileup effect caused by the interaction of the reconnection outflows with ambient tail plasma similar to the snow-plow mechanism discussed by Lapenta and Bettarini ( 2011 ).…”

Section: Onset Mechanismsmentioning

confidence: 60%

Explosive Magnetotail Activity

et al. 2019

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Modes and manifestations of the explosive activity in the Earth’s magnetotail, as well as its onset mechanisms and key pre-onset conditions are reviewed. Two mechanisms for the generation of the pre-onset current sheet are discussed, namely magnetic flux addition to the tail lobes, or other high-latitude perturbations, and magnetic flux evacuation from the near-Earth tail associated with dayside reconnection. Reconnection onset may require stretching and thinning of the sheet down to electron scales. It may also start in thicker sheets in regions with a tailward gradient of the equatorial magnetic field ; in this case it begins as an ideal-MHD instability followed by the generation of bursty bulk flows and dipolarization fronts. Indeed, remote sensing and global MHD modeling show the formation of tail regions with increased , prone to magnetic reconnection, ballooning/interchange and flapping instabilities. While interchange instability may also develop in such thicker sheets, it may grow more slowly compared to tearing and cause secondary reconnection locally in the dawn-dusk direction. Post-onset transients include bursty flows and dipolarization fronts, micro-instabilities of lower-hybrid-drift and whistler waves, as well as damped global flux tube oscillations in the near-Earth region. They convert the stretched tail magnetic field energy into bulk plasma acceleration and collisionless heating, excitation of a broad spectrum of plasma waves, and collisional dissipation in the ionosphere. Collisionless heating involves ion reflection from fronts, Fermi, betatron as well as other, non-adiabatic, mechanisms. Ionospheric manifestations of some of these magnetotail phenomena are discussed. Explosive plasma phenomena observed in the laboratory, the solar corona and solar wind are also discussed.

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Section: Onset Mechanismsmentioning

confidence: 60%

Explosive Magnetotail Activity

et al. 2019

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“…This can be a cold-ion drift, and is found near the separatrix of the magnetic reconnection topology (e.g. Nakabayashi and Machida, 1997;Fujimoto and Machida, 2007).…”

Section: Resultsmentioning

confidence: 99%

Statistical visualization of the Earth's magnetotail based on Geotail data and the implied substorm model

et al. 2009

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Abstract. We investigated the temporal and spatial development of the near-Earth magnetotail during substorms based on multi-dimensional superposed-epoch analysis of Geotail data. The start time of the auroral break-up (t=0) of each substorm was determined from auroral data obtained by the Polar and IMAGE spacecraft. The key parameters derived from the plasma, magnetic-field, and electric-field data from Geotail were sorted by their meridional X(GSM)-Z(proxy) coordinates.The results show that the Poynting flux toward the plasmasheet center starts at least 10 min before the substorm onset, and is further enhanced at X∼−12 R E (Earth radii) around 4 min before the onset. Simultaneously, large-amplitude fluctuations occurred, and earthward flows in the central plasma sheet between X∼−11 R E and X∼−19 R E and a duskward flow around X=−10 R E were enhanced. The total pressure starts to decrease around X=−16 R E about 4 min before the onset of the substorm. After the substorm onset, a notable dipolarization is observed and tailward flows commence, characterised by southward magnetic fields in the form of a plasmoid.We confirm various observable-parameter variations based on or predicted by the relevant substorm models; however, none of these can explain our results perfectly. Therefore, we propose a catapult (slingshot) current-sheet relaxation model, in which an earthward convective flow produced by catapult current-sheet relaxation and a converted duskward flow near Correspondence to: S. Machida (machida@kugi.kyoto-u.ac.jp) the Earth are enhanced through flow braking around 4 min before the substorm onset. These flows induce a ballooning instability or other instabilities, causing the observed current disruption. The formation of the magnetic neutral line is a natural consequence of the present model, because the relaxation of a highly stretched catapult current-sheet produces a very thin current at its tailward edge being surrounded by intense earthward and tailward magnetic fields which were formerly the off-equatorial lobe magnetic fields. This location is the boundary between a highly stressed catapult current sheet and a Harris-type current sheet characterized by little stress. In addition, the flows induced around the boundary toward the current-sheet center may enhance the formation of the magnetic neutral line and the efficiency of magnetic reconnection. After magnetic reconnection is induced, it plays a significant role in driving the substorm.

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“…[24][25][26] The following works have revealed the internal structure of an outflow exhaust 27,28 and associated ion dynamics. [27][28][29][30][31] For example, there is usually an current layer at the center of the exhaust. [26][27][28] However, since hybrid models ignore electron physics, it is not clear whether these results are reliable near the X-type region.…”

Section: Introductionmentioning

confidence: 99%

Kinetic aspects of the ion current layer in a reconnection outflow exhaust

et al. 2013

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Kinetic aspects of the ion current layer at the center of a reconnection outflow exhaust near the X-type region are investigated by a two-dimensional particle-in-cell (PIC) simulation. The layer consists of magnetized electrons and unmagnetized ions that carry a perpendicular electric current. The ion fluid appears to be nonideal, sub-Alfvénic, and nondissipative. The ion velocity distribution functions contain multiple populations, such as global Speiser ions, local Speiser ions, and trapped ions. The particle motion of the local Speiser ions in an appropriately rotated coordinate system explains the ion fluid properties very well. The trapped ions are the first demonstration of the regular orbits in the chaotic particle dynamics [Chen and Palmadesso, J. Geophys. Res., 91, 1499Res., 91, (1986] in self-consistent PIC simulations. They would be observational signatures in the ion current layer near reconnection sites.

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Electromagnetic hybrid‐code simulation of magnetic reconnection: Velocity distribution functions of accelerated ions

Cited by 21 publications

References 9 publications

Explosive Magnetotail Activity

Explosive Magnetotail Activity

Statistical visualization of the Earth's magnetotail based on Geotail data and the implied substorm model

Kinetic aspects of the ion current layer in a reconnection outflow exhaust

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