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The semiannual variation of transpolar arc incidence and its relationship to the Russell–McPherron effect

Earth and Planetary Physics 2020年第6期4卷 619-626页

作者： Tao Tang Jun Yang QuanQi Shi AnMin Tian Shi-Chen Bai alexander william degeling SuiYan Fu JingXian Liu Tong Shao ZeYuan Sun Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsInstitute of Space SciencesShandong UniversityWeihai Shandong 264209China Institute of Space Physics and Applied Technology Peking UniversityBeijing 100871China

Earth’s aurora is a luminescent phenomenon generated by the interaction between magnetospheric precipitating particles and the upper atmosphere;it plays an important role in magnetosphere–ionosphere(M-I)*** transpolar arc(TPA)is a discrete auroral arc distributed in the noon-midnight direction poleward of the auroral oval and connects the dayside to the nightside sectors of the auroral *** the seasonal variation of TPA events can help us better understand the long-term variation of the interaction between the solar wind,the magnetosphere,and M-I ***,a statistical study of the seasonal variation of TPA incidence has not previously been carried *** this paper,we have identified 532 TPA events from the IMAGE database(2000–2005)and the Polar database(1996–2002),and calculated the incidence of TPA events for different *** find a semiannual variation in TPA *** peaks in the incidence of TPAs occur in March and September;a less pronounced peak appears in *** also examine seasonal variation in the northward interplanetary magnetic field(IMF)over the same time *** intensity and occurrence rate of the northward IMF exhibit patterns similar to that of the TPA *** studied IMF Bz before TPA onset,we find that strong and steady northward IMF conditions are favorable for TPA *** suggest that the semiannual variation observed in TPA incidence may be related to the Russell–McPherron(R-M)effect due to the projection effect of the IMF By under northward IMF conditions.

关键词： transpolar arc incidence interplanetary magnetic field Russell-McPherron effect semiannual variation

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Statistical properties of kinetic-scale magnetic holes in terrestrial space

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Earth and Planetary Physics 2021年第1期5卷 63-72页

作者： ShuTao Yao ZongShun Yue QuanQi Shi alexander william degeling HuiShan Fu AnMin Tian Hui Zhang Andrew Vu RuiLong Guo ZhongHua Yao Ji Liu Qiu-Gang Zong XuZhi Zhou JingHuan Li WenYa Li HongQiao Hu YangYang Liu WeiJie Sun Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai Shandong 264209China State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China School of Space and Environment Beihang UniversityBeijing 100191China Physics Department and Geophysical Institute University of Alaska FairbanksFairbanksAK99775USA Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Laboratoire de Physique Atmosphérique et Planétaire STAR InstituteUniversitéde LiègeLiègeB-4000Belgium School of Earth and Space Sciences Peking UniversityBeijing 100871China SOA Key Laboratory for Polar Science Polar Research Institute of ChinaShanghai 200136China Department of Climate and Space Sciences and Engineering University of MichiganAnn ArborMI48109USA

Kinetic-scale magnetic holes(KSMHs)are structures characterized by a significant magnetic depression with a length scale on the order of the proton *** structures have been investigated in recent studies in near-Earth space,and found to be closely related to energy conversion and particle acceleration,wave-particle interactions,magnetic reconnection,and turbulence at the ***,there are still several major issues of the KSMHs that need further study—including(a)the source of these structures(locally generated in near-Earth space,or carried by the solar wind),(b)the environmental conditions leading to their generation,and(c)their spatio-temporal *** this study,KSMHs in near-Earth space are investigated statistically using data from the Magnetospheric Multiscale *** 200,000 events were observed from September 2015 to March *** rates of such structures in the solar wind,magnetosheath,and magnetotail were *** find that KSMHs occur in the magnetosheath at rates far above their occurrence in the solar *** indicates that most of the structures are generated locally in the magnetosheath,rather than advected with the solar ***,KSMHs occur in the downstream region of the quasi-parallel shock at rates significantly higher than in the downstream region of the quasi-perpendicular shock,indicating a relationship with the turbulent plasma *** to the magnetopause,we find that the depths of KSMHs decrease as their temporal-scale *** also find that the spatial-scales of the KSMHs near the subsolar magnetosheath are smaller than those in the ***,their global distribution shows a significant dawn-dusk asymmetry(duskside dominating)in the magnetotail.

关键词： kinetic scale magnetic hole magnetic dip electron vortex turbulence

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Analytical model test of methods to find the geometry and velocity of magnetic structures

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Science China(Technological Sciences) 2019年第6期62卷 1003-1014页

作者： TIAN AnMin SHI QuanQi degeling alexander william BAI ShiChen YAO ShuTao ZHANG Shuai Shandong Provincial Key Laboratory of Optical Astronomy and Solar- Terrestrial Environment School of Space Science and Physics Shandong University Weihai 264209 China State Key Laboratory of Space Weather Chinese Academy of Sciences Beijing 100190 China

It is important to determine the dimensionality and velocity information in the study of spatial magnetic structures. Many data analysis theories/techniques are based on the assumption of one or two dimensions. For example, the Grad-Shafranov(GS)reconstruction method assumes a dimensionality of two or less. The Minimum Direction Derivative(MDD) method provides an indication of the dimensionality. For the structure velocity, the components in each dimensionality can be calculated by SpatioTemporal Difference analysis(STD). In order to improve the convenience of use of MDD method, a new parameter Dm quantifying the dimensionality based on MDD eigenvalues is introduced in this paper. The influences of noise/turbulence,separation distance and tetrahedron configuration on MDD and the evaluation of Dmare systematically tested using two analytical models for magnetic structures, representing a magnetic mirror and magnetic flux rope. We tested and gave the threshold values of three quality indicators for MDD results using the flux rope model. We also show that the error induced by turbulence is comparable to that of random noise when the turbulence scales are less than the spacecraft separation. Besides, the accuracy of STD velocity estimation will also be influenced by turbulence for cases with excessively high data time *** using Dm, we show that an ideal model of a mirror-like structure can be divided into one dimension(1-D) and three dimension(3-D) regions. This restricts the applicability of the GS method in mirror-like structures. For example, in a given reconstruction range, the GS error increased from less than 7% to more than 15% by using the data along trajectories in 1-D and 3-D regions as predicated by Dm. Thus, it is important to estimate the structure dimensionality, which can be further used to estimate the reliability of the GS reconstruction map.

关键词： magnetic structure MDD method model test GS reconstruction dimensionality

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Propagation properties of foreshock cavitons: Cluster observations

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Science China(Technological Sciences) 2020年第1期63卷 173-182页

作者： WANG MengMeng YAO ShuTao SHI QuanQi ZHANG Hui TIAN AnMin degeling alexander william ZHANG Shuai GUO RuiLong SUN WeiJie LIU Ji BAI ShiChen SHEN XiaoChen ZHU XiaoQiong FU SuiYan PU ZuYin School of Space Science and Physics Shandong UniversityWeihai 264209China National Space Science Center Chinese Academy of SciencesBeijing 100190China Geophysical Institute University of Alaska FairbanksFairbanksAlaska 99775USA Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China Department of Climate and Space Sciences and Engineering University of MichiganAnn Arbor 48113USA Institute of Space Physics and Applied Technology Peking UniversityBeijing 100871China

Foreshock cavitons are transient phenomena observed in the terrestrial foreshock *** are characterized by a simultaneous depression of magnetic field magnitude and plasma density,which are bounded with enhancements of these two parameters and surrounded by ultralow frequency(ULF)*** studies focused on the interplanetary magnetic field(IMF)conditions,solar wind(SW)conditions,and the growth of the foreshock waves related to the generation of foreshock ***,a multipoint spacecraft analysis method using Cluster data was applied to analyze only two foreshock cavitons,and this method did not consider *** this study,multipoint spacecraft analysis methods,including the timing method,the minimum directional derivative(MDD)method,and the spatiotemporal difference(STD)method are applied to determine the velocity in both spacecraft and solar wind *** propagation properties show good agreement with previous results from simulations and observations that most cavitons move sunward in the solar wind frame,with the velocities larger than the Alfvén *** propagation properties of foreshock cavitons support the formation mechanism of cavitons in previous simulations,which suggested that cavitons are formed due to the nonlinear evolution of compressive ULF *** find that there is clear decreasing trend between the size of cavitons and their velocity in the solar wind *** addition,the timing method considering errors has been applied to study the evolution properties by comparing the velocities with errors of the leading and trailing edges,and we identify three stable cavitons and one contracting caviton,which has not been studied *** cavitons should remain stable when they travel toward the Earth’s bow *** relationship between the size of foreshock cavitons and their distance from the bow shock is also discussed.

关键词： foreshock transient phenomena cavitons nonlinear evolution of ULF waves propagation and evolution properties of structures multipoint spacecraft methods

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