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The response of plasma parameters and energy transport in the plasma sheet to interplanetary magnetic field B_z

Science China(Technological Sciences) 2021年第7期64卷 1528-1534页

作者： REN GanMing CAO JinBin YANG Jian DUNLOP Malcolm Wray School of space and environment Beihang UniversityBeijing100191China key laboratory of space environment monitoring and information processing of miit Beijing102206China

We use 9 years data of Cluster to study the dependencies of plasma parameters and energy transport in the plasma sheet on the lasting time of northward/southward interplanetary magnetic field(IMF). The plasma parameters and energy transport in the plasma sheet always respond to the change of IMF direction by more or less time. The ion density starts to increase/decrease remarkably at 80 min after northward/southward IMF turning. The ion temperature starts to decrease at 25 min after northward IMF turning, whereas it starts to increase at 80 min after southward IMF turning. The earthward convection velocity within15 min after northward IMF turning almost equals to that within 15 min period after southward IMF turning. However at time greater than 15 min after southward IMF turning, the earthward convection velocity under southward IMF starts to remarkably increase. The response time(15 min) of magnetospheric convection velocity is well consistent with the response times of nightside ionospheric convection to southward IMF turning. The enthalpy flux is larger than kinetic flux by about three orders of magnitudes, and thus the enthalpy flux plays a dominant role in the plasma sheet energy transport. The enthalpy flux does not weaken immediately after northward IMF turning. The enthalpy flux within 15 min after northward IMF turning is comparable to or even slightly larger than that within 15 min after southward IMF. The enthalpy flux starts to decrease at times greater than15 min after northward IMF turning, whereas it starts to increase at times greater than 15 min after southward IMF turning. The result that the enhanced energy transport during the 15 min period after northward IMF turning may explain previous observation that substorms frequently occur shortly after northward IMF turning.

关键词： plasma sheet energy transport enthalpy flux response time

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A normalized statistical study of Earth’s cusp region based on nine-years of Cluster measurements

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Earth and Planetary Physics 2020年第3期4卷 266-273页

作者： Chao Xiao WenLong Liu DianJun Zhang Zhao Zhang School of space and environment Beihang UniversityBeijing 102206China key laboratory of space environment monitoring and information processing of miit Beijing 102206China

Nine years(2001–2009)of data from the Cluster spacecraft are analyzed in this study of the Earth’s mid-and high-altitude(2–9RE)*** of the cusp region,and its location and size in the Solar Magnetic coordinate system,are studied *** survey shows that(1)the relationships between X and Z are nearly linear for the poleward,equatorward boundaries and the center of the cusp;(2)the relationship between cusp width in the X direction and Z can be expressed by a quadratic function;(3)the cusp region is almost dawn-dusk symmetric for the cusp width in the X *** on topology information,a new normalized statistical methodology is developed to organize the measurements of cusp crossings to obtain distributions of magnetic field and plasma parameters in the XZ *** statistical results show that(1)Bx is mostly negative and Bz is always negative;(2)proton velocity is found to be positive for Vx and Vz at low altitudes,while Vx and Vz are negative on the equator side and negative Vx and positive Vz on the pole side at high altitudes;(3)proton density is higher on the equator side than on the pole *** reported here will be useful in suggesting directions for future cusp research.

关键词： cusp statistical study new methodology topology

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A storm-time ring current model(STRIM)

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Science China Technological Sciences 2024年第12期67卷 3890-3908页

作者： YU YiQun MA LongXing WEI ZiMing AN DePeng WU HaiJun LU HaoYu CAO JinBin School of space and Earth Sciences Beihang University key laboratory of space environment monitoring and information processing Ministry of Industry and Information Technology

The ring current, one of the most important current systems around the Earth, intensifies during geomagnetic storms and is believed to be the main reason for large-scale magnetic field perturbations in the geospace environment. Understanding how the ring current builds up and evolves during geomagnetic storms is of great importance not only for advancing the knowledge of the Sun-Earth system but also for improving the modeling capability of predicting hazardous space weather events. Focusing on the national strategic needs in the space weather prediction, in this study, we establish a ring current model named storm time ring current model(STRIM). The STRIM comprehensively embraces key physical processes in association with ring current dynamics,including plasma source injections from the nightside plasmasheet and transport around the Earth, charge-exchange with neutral hydrogens, Coulomb collisions with thermal plasma, wave-particle interactions, field line curvature scattering, and precipitation loss down to the upper atmosphere. The electric fields needed for particle motion can be optionally taken from empirical models or self-consistently calculated, while the magnetic field configuration is obtained from Tsyganenko 2005 model. Simulation results are verified against the published literature and validated with in-situ satellite or ground-based observations and are found to have the same high-level capability and fidelity as other well-known published models. We also discuss future tasks of fostering the model's performance and potential applications.

关键词： kinetic ring current models bounce-averaged Fokker-Planck equation Earth inner magnetosphere ring current dynamics magnetic storms

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Validation of the use of THEMIS-B and THEMIS-C as a near-Earth solar wind monitor

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Earth and Planetary Physics 2022年第6期6卷 546-554页

作者： DianJun Zhang WenLong Liu Zhao Zhang School of space and environment Beihang UniversityBeijing 100191China key laboratory of space environment monitoring and information processing Ministry of Industry and Information TechnologyBeijing 100191China

Two THEMIS(Time History of Events and Macroscale Interactions during Substorms)spacecraft,B and C,began orbiting the Moon in 2011 and have since provided routine measurements of the plasma conditions in the lunar *** this study,we systematically compare these measurements in near-Earth space with solar wind measurements obtained from the Lagrangian 1(L1)point and propagated to the Earth,including measurements in the OMNI database and from the Wind spacecraft.A statistical comparison between THEMIS data and data from the OMNI database from September 2011 to December 2017 showed that the Y and Z components of the magnetic field and the flow speed are generally consistent between the two data *** ion number density and the dynamic pressure measured by THEMIS in near-Earth space are lower than those in the OMNI database,suggesting possible variation in the solar wind environment while propagating from the L1 point to near-Earth *** further show two examples in which near-Earth solar wind measurements are applied in calculating the magnetopause location and in quantifying the magnetic field response to interplanetary *** examples suggest that using solar wind data from near-Earth space achieves better results than using solar wind data from the L1 *** results provide validation of THEMIS-B and THEMIS-C as an alternative monitor of the near-Earth solar wind environment.

关键词： interplanetary shocks solar wind magnetosphere

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Magnetospheric Physics in China:2020-2021

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空间科学学报 2022年第4期42卷 628-652页

作者： CAO Jinbin YANG Junying space Science Institute School of Space and EnvironmentBeihang UniversityBeijing 100191 key laboratory of space environment monitoring and information processing Ministry of Industry and Information TechnologyBeijing 100191

In the past two years,many progresses were made in magnetospheric physics by the data of OMNI,SuperMAG networks,Double Star Program,Cluster,THEMIS,RBSP,DMSP,DEMETER,NOAA,Van Allen Probes,GOES,Geotail,Swarm,MMS,BeiDa,Fengyun,ARTEMIS,MESSENGER,Juno,Chinese Mars ROVER,MAVEN,Tianwen-1,Venus Express,Lunar Prospector e.g.,or by computer *** paper briefly reviews these works based on 356 papers published from January 2020 to December *** subjects covered various sub-branches of Magnetospheric Physics,including solar wind-magnetosphere-ionosphere interaction,inner magnetosphere,outer magnetosphere,magnetic reconnection,planetary magnetosphere.

关键词： Solar wind-magnetosphere-ionosphere interaction Inner magnetosphere Outer magnetosphere Magnetic reconnection Planetary magnetosphere

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Collisionless magnetic reconnection in the magnetosphere

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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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Energy conversion due to non-ideal electric field in separatrix region of magnetotail reconnection

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Earth and Planetary Physics 2024年第5期8卷 787-796页

作者： YiNan Liu Keizo Fujimoto JianQiang Wang XiaoChuan Duan School of space and environment Beihang UniversityBeijing 102206China key laboratory of space environment monitoring and information processing Ministry of Industry and Information TechnologyBeijing 102206China School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China

A recent satellite observation has revealed the presence of energy conversion in the separatrix region(SR)of magnetotail reconnection,driven by perpendicular *** investigated this phenomenon by means of particle-in-cell simulations in two-dimensional(2D)and three-dimensional(3D)*** result indicates that in the 2D simulation,energy conversion in the SR is dominated by parallel components,with the main influencing factor being the parallel electric field,which is not consistent with the ***,a case that is similar to the observation is found in the 3D simulation,suggesting that the observation result may be attributed to the 3D *** findings provide a potential explanation for the satellite observation.

关键词： magnetic reconnection energy conversion PIC simulation separatrix region

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On the ion distributions at the separatrices during symmetric magnetic reconnection

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Earth and Planetary Physics 2021年第2期5卷 205-217页

作者： HongTao Huang YiQun Yu JinBin Cao Lei Dai RongSheng Wang School of space and environment Beihang UniversityBeijing 100191China key laboratory of space environment monitoring and information processing Ministry of Industry and Information TechnologyBeijing 100191China State key laboratory of space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China key laboratory of Geospace environment Department of Geophysics and Planetary ScienceUniversity of Science and Technology of ChinaHefei 230026China

A particle-in-cell simulation of symmetric reconnection with zero guide field is carried out to understand the dynamics of ions along the *** the investigation of ion velocity distributions at different moments and locations along the separatrices,a typical distribution is found:two counter-streaming populations in the perpendicular direction,with another two populations accelerated into distinct energy levels in the parallel *** tracing of ions reveals that the counter-streaming cores are mostly composed of ions initially located at the same side of the separatrix,while the other two accelerated populations in the parallel direction are composed of ions crossing through the neutral *** analysis of energy conversion of these populations,it is found that the ion energization along the separatrix is attributable primarily to the Hall electric field,while that in the region between the two separatrices is caused primarily by the induced reconnection electric *** the counter-streaming population,the low-energy ions that cross the separatrix twice are affected by both Hall and reconnection electric fields,while the high-energy ions that directly enter the separatrix from the unperturbed plasma are energized mainly by the Hall electric *** the two energized populations in the parallel direction,the ions with lower-energy are accelerated mainly by the in-plane electric field and the Hall electric field on the opposite side of the separatrix,whereas the ions with higher-energy not only experience the same energization process but also are constantly accelerated by the reconnection electric field.

关键词： magnetic reconnection particle-in-cell simulation energetic particles

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Coupling plasma plume of a low-power magnetically shielded Hall thruster with a hollow cathode

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Chinese Journal of Aeronautics 2020年第12期33卷 3018-3026页

作者： Guangchuan ZHANG Junxue REN Wei LIANG Ning OUYANG Chao LU Haibin TANG School of space and environment Beihang UniversityBeijing 100083China School of Astronautics Beihang UniversityBeijing 100083China Shanghai Institute of space Propulsion Shanghai 201112China key laboratory of spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeijing 100083China laboratory of space environment monitoring and information processing Ministry of Industry and Information TechnologyBeijing 100083China

The coupling region of a Hall thruster with a hollow cathode is the region between the cathode and the thruster *** characteristics of plasma in that region are complicated and strongly associated with the thruster working conditions and the cathode *** this paper,a laboratory 100 W class magnetically shielded Hall thruster was coupled with a hollow *** imaging and electrostatic probe were employed to monitor and scan the plasma *** characteristics in the coupling region in non-self-sustained mode and self-sustained mode were *** of the coupling plume with the cathode position was *** show that,when turning the thruster into self-sustained mode or moving the cathode further away axially,the discharge current can be reduced by 6.4–10.6%restraining the electron current and improving *** particular,when the cathode is moved further,the electron conduction near the channel walls is *** electron current is reduced by 27.4%and the ion beam current is increased by 7%.Overall,this work shows that the working mode of the thruster and the position of the cathode greatly affect the coupling plasma *** play an important role in improving the utilizations of propellant and current.

关键词： Coupling region Electron conduction Hall thruster Hollow cathode Utilizations of propellant and current

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Electron population properties with different energies in a helicon plasma source

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Plasma Science and Technology 2021年第1期23卷 48-55页

作者： Zun ZHANG Zhe ZHANG Haibin TANG Jiting OUYANG School of space and environment Beihang UniversityBeijing 100191People’s Republic of China key laboratory of space environment monitoring and information processing of miit People’s Republic of China Shanghai Institute of space Propulsion Shanghai Engineering Research Center of Space EngineShanghai 201112People’s Republic of China School of Instrumentation and Optoelectronic Engineering Beihang UniversityBeijing 100191People’s Republic of China School of Physics Beijing Institute of TechnologyBeijing 100081People’s Republic of China

The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of *** with electrostatic diagnostics,the optical method is independent of the radio frequency(RF)noise,magnetic field,and electric *** this paper,an optical emission spectroscope was used to determine the plasma emission spectra,electron excitation energy population distributions(EEEPDs),growth rates of low-energy and highenergy electrons,and their intensity jumps with input *** 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into *** discrete EEEPD has two clear different regions,namely the low-energy electron excitation region(neutral lines with threshold energy of13–15 eV)and the high-energy electron excitation region(ionic lines with threshold energy?19 e V).The EEEPD variations with different diameters of discharge tubes(20 mm,40 mm,and 60 mm)and different input RF powers(200–1800 W)were *** normalized intensity comparison of the ionic and neutral lines,the growth rate of the ionic population was higher than the neutral one,especially when the tube diameter was less than 40 mm and the input power was higher than 1000 ***,we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled(H)mode to helicon(W)mode;therefore,the determination of W mode needs to be carefully considered.

关键词： electric propulsion helicon plasma plasma diagnostics optical emission spectroscope electron excitation energy population distribution

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