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collisionless magnetic reconnection in the magnetosphere

Chinese Physics B 2022年第8期31卷 101-116页

作者： Quanming Lu Huishan Fu Rongsheng Wang San Lu CAS Key Laboratory of Geospace Environment School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology Hefei 230026China School of Space and Environment Beihang UniversityBeijing 100191China Key Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100191China

magnetic reconnection underlies the physical mechanism of explosive phenomena in the solar atmosphere and planetary magnetospheres, where plasma is usually collisionless. In the standard model of collisionless magnetic reconnection,the diffusion region consists of two substructures: an electron diffusion region is embedded in an ion diffusion region,in which their scales are based on the electron and ion inertial lengths. In the ion diffusion region, ions are unfrozen in the magnetic fields while electrons are magnetized. The resulted Hall effect from the different motions between ions and electrons leads to the production of the in-plane currents, and then generates the quadrupolar structure of out-of-plane magnetic field. In the electron diffusion region, even electrons become unfrozen in the magnetic fields, and the reconnection electric field is contributed by the off-diagonal electron pressure terms in the generalized Ohm’s law. The reconnection rate is insensitive to the specific mechanism to break the frozen-in condition, and is on the order of 0.1. In recent years, the launching of Cluster, THEMIS, MMS, and other spacecraft has provided us opportunities to study collisionless magnetic reconnection in the Earth’s magnetosphere, and to verify and extend more insights on the standard model of collisionless magnetic reconnection. In this paper, we will review what we have learned beyond the standard model with the help of observations from these spacecraft as well as kinetic simulations.

关键词： collisionless magnetic reconnection magnetosphere

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The effect of the guide field on energy conversion during collisionless magnetic reconnection

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Earth and Planetary Physics 2023年第4期7卷 436-444页

作者： Hui Xiao ZhiHong Zhong Meng Zhou YongYuan Yi LiangJin Song Ye Pang XiaoHua Deng School of Physics and Materials Science Nanchang UniversityNanchang 330031China Institute of Space Science and Technology Nanchang UniversityNanchang 330031China School of Resources and Environment Nanchang UniversityNanchang 330031China

magnetic reconnection is well known as an efficient mechanism for transferring magnetic energy into plasma ***,how the energy conversion and partition between different species is influenced by the shear angle of the reconnecting magnetic component(i.e.,the guide field strength)is not well *** 2.5-dimensional particle-in-cell simulations,we investigated the energy conversion in reconnection with different guide *** found that the overall energy conversion first decreases steeply and then increases slowly when the guide field increases fromB_(g)=0 toB_(g)=*** increase in energy conversion in the large guide field regime is due to the electron energy gain through the perpendicular channelJ_(⊥)·E_(⊥).The overall energy conversion is predominantly contributed byJ_(⊥)·E_(⊥) rather thanJ||E||.We further find that energy conversion mainly occurs within the reconnection front and the flux pileup ***,the contribution from the fore reconnection front becomes important in large guide field regimes(3

关键词： collisionless magnetic reconnection energy conversion guide field particle-in-cell simulation

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Ion and electron motions in the outer electron diffusion region of collisionless magnetic reconnection

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Earth and Planetary Physics 2024年第3期8卷 472-478页

作者： Cong Chang QuanMing Lu San Lu Kai Huang RongSheng Wang Deep Space Exploration Laboratory School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences(CAS)Center for Excellence in Comparative Planetology CAS Key Laboratory of Geospace EnvironmentHefei 230026China Collaborative Innovation Center of Astronautical Science and Technology Harbin 150001China

Two-dimensional particle-in-cell simulations are performed to study the coupling between ion and electron motions in collisionless magnetic *** electron diffusion region(EDR),where the electron motions are demagnetized,is found to have a two-layer structure:an inner EDR near the reconnection site and an outer EDR that is elongated to nearly 10 ion inertial lengths in the outflow *** the inner EDR,the speed of the electron outflow increases when the electrons move away from the X *** the outer EDR,the speed of the electron outflow first increases and then decreases until the electrons reach the boundary of the outer *** the boundary of the outer EDR,the magnetic field piles up and forms a depolarization *** the perspective of the fluid,a force analysis on the formation of electron and ion outflows has also been *** the X line,the electrons are accelerated by the reconnection electric field in the out-of-plane *** the electrons move away from the X line,we find that the Lorentz force converts the direction of the accelerated electrons to the x direction,forming an electron *** electric field forces and electron gradient forces tend to drag the electron *** acceleration along the x direction is caused by the Lorentz force,whereas the pressure gradient force tends to decelerate the ion *** these two terms are important,their effects on ions are almost *** Hall electric field force does positive work on ions and is not *** ions are continuously accelerated,and the ion and electron outflow velocities are almost the same near the depolarization front.

关键词： collisionless magnetic reconnection electron diffusion region force analysis particle-in-cell simulation

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Stochastic Acceleration of Electrons by the Right-Hand Extraordinary Mode in the High Density Plasma Region

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Chinese Physics Letters 2005年第6期22卷 1552-1555页

作者：肖伏良郑惠南王水 DepartmentofPhysicsandElectronicSciences ChangshaUniversityofScienceandTechnologyChangsha410076 SchoolofEarthandSpaceSciences UniversityofScienceandTechnologyofChinaHefei230026

The resonant acceleration of electrons by the superluminous R-X mode isevaluated in the high density plasma region of Earth, specifically around the geostationary *** corresponding resonant frequency range together with the harmonic N required for producing asignificant acceleration is studied in detail. It is found that the P stochastic acceleration isbasically controlled by the harmonic N and a dimensionless parameter alpha = vertical bar Omega(e)(2vertical bar)/omega(pe)(2) (where vertical bar Omega(e)vertical bar and omega(pe) are the electrongyrofrequency and plasma frequency respectively). For alpha = 0.1 (around the geostationary orbit),there are riot gyroresonances occurring between electrons and right-hand extraordinary-modeelectromagnetic waves until higher harmonics N >= 4; while for alpha = 0.5, the gyroresonance beginsat N = 2. Substantial acceleration of electrons by the right-hand extraordinary mode is possiblefor those higher harmonic (N > 1) resonances over a wide range of wave normal angles theta. Thisindicates that higher harmonic resonance can play an important role on the electron acceleration inthe high density plasma region (alpha < 1).

关键词： collisionless magnetic reconnection WAVES MAGNETOSPHERE INSTABILITY

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Excitation of Whistler-Mode （Chorus） Emissions during Terrestrial Substorms

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Chinese Physics Letters 2005年第9期22卷 2451-2454页

作者：肖伏良赵华贺慧勇 Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 Department of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410076

The enhanced growth rate of whistler mode waves has been evaluated during an injection event associated with an isolated terrestrial substorm that occurred at 23：00 UT, on January 21, 1991. The electron phase space density observed by an LEPA instrument on the board of the CRRES spacecraft is modelled by using a bi-loss-cone distribution function （composed of a high anisotropic component and a quasi-isotropic component）. During the injection event, the path integrated gain may increase by a factor of 5 over a frequency range near a few tenths of the electron gyrofrequency, which is consistent with the enhancement observed in the CRRES plasma wave experiment （PWE） emissions. Scattering of electrons by the enhanced whistler mode waves causes the pitch angle distribution of resonant electrons to a quasi isotropic （fiat-top） distribution during the terrestrial substorm injection event.

关键词： collisionless magnetic reconnection ACCELERATION INSTABILITY ELECTRONS PLASMA WAVES

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Second-Order Resonant Interaction of Ring Current Protons with Whistler-Mode Waves

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Chinese Physics Letters 2008年第1期25卷 336-339页

作者：肖伏良陈良旭贺慧勇周庆华 School of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410076 State Key Laboratory of Space Weather PO Box 8701 Beijing 100080

We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory. The diffusion coefficients are proportional to the electric field amplitude E, much greater than those for the regular first-order resonance, which are proportional to the electric field amplitudes square E^2. Numerical calculations for the pitch angle scattering are performed for typical energies of protons Ek = 50 keV and 100 keV at locations L = 2 and L = 3.5. The timescale for the loss process of protons by the Whistler waves is found to approach one hour, comparable to that by the EMIC waves, suggesting that Whistler waves may also contribute significantly to the ring current decay under appropriate conditions.

关键词： PITCH-ANGLE DIFFUSION RADIATION BELT PROTONS collisionless magnetic reconnection DUCTED PLASMASPHERIC HISS ION-CYCLOTRON WAVES ELECTRONS MAGNETOSPHERE ACCELERATION COEFFICIENTS STORMS

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无碰撞磁重联中的混沌感应电阻及其应用（英文）

无碰撞磁重联中的混沌感应电阻及其应用（英文）

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中国天文学会2021年学术年会

作者：吴德金紫金山天文台

It is one of the most puzzling problems in the plasma physics to understand the anomalous resistivity in collisionless magnetic reconnection that is believed extensively to be responsible for the energy release of various eruptive phenomena in space and solar *** chaos-induced resistivity due to chaotic motions of charged particles in reconnect current sheets is one of possible mechanisms for the anomalous *** talk will present the main characteristics of the chaos-induced resistivity in various reconnection current sheets with different magnetic configurations and their possible applications in some active phenomena in space and solar plasmas.

关键词： Chaos-Induced Rsistivity collisionless magnetic reconnection

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