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Deformations at Earth’s dayside magnetopause during quasi-radial IMF conditions:Global kinetic simulations and Soft X-ray Imaging

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Earth and Planetary Physics 2024年第1期8卷 59-69页

作者： ZhongWei Yang RiKu Jarvinen XiaoCheng Guo TianRan Sun Dimitra Koutroumpa George K.Parks Can Huang BinBin Tang QuanMing Lu Chi Wang State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China Finnish Meteorological Institute FI-00101 HelsinkiFinland LATMOS/IPSL CNRSUVSQ UniversitéParis-SaclaySorbonne UniversitéGuyancourt78280France Space Sciences Laboratory University of CaliforniaBerkeleyCalifornia 94720USA CAS Engineering Laboratory for Deep Resources Equipment and Technology Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029 China Deep Space Exploration Laboratory/School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China

The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)is a joint mission of the European Space Agency(ESA)and the Chinese Academy of Sciences(CAS).Primary goals are investigating the dynamic response of the Earth's magnetosphere to the solar wind(SW)impact via simultaneous in situ magnetosheath plasma and magnetic field measurements,X-Ray images of the magnetosheath and magnetic cusps,and UV images of global auroral distributions.Magnetopause deformations associated with magnetosheath high speed jets(HSJs)under a quasi-parallel interplanetary magnetic field condition are studied using a threedimensional(3-D)global hybrid simulation.Soft X-ray intensity calculated based on both physical quantities of solar wind proton and oxygen ions is compared.We obtain key findings concerning deformations at the magnetopause:(1)Magnetopause deformations are highly coherent with the magnetosheath HSJs generated at the quasi-parallel region of the bow shock,(2)X-ray intensities estimated using solar wind h+and self-consistentO7+ions are consistent with each other,(3)Visual spacecraft are employed to check the discrimination ability for capturing magnetopause deformations on Lunar and polar orbits,respectively.The SMILE spacecraft on the polar orbit could be expected to provide opportunities for capturing the global geometry of the magnetopause in the equatorial plane.A striking point is that SMILE has the potential to capture small-scale magnetopause deformations and magnetosheath transients,such as HSJs,at medium altitudes on its orbit.Simulation results also demonstrate that a lunar based imager(e.g.,Lunar Environment heliospheric X-ray Imager,LEXI)is expected to observe a localized brightening of the magnetosheath during HSJ events in the meridian plane.These preliminary results might contribute to the pre-studies for the SMILE and LEXI missions by providing qualitative and quantitative soft X-ray estimates of dayside kinetic processes.

关键词： collisionless shock SMILE mission foreshock

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Statistical study of magnetic holes in the upstream region of Mercury’s bow shock

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Earth and Planetary Physics 2024年第2期8卷 326-337页

作者： GuoQiang Wang SuDong Xiao MingYu Wu YuanQiang Chen TieLong Zhang Institute of Space Science and Applied Technology Harbin Institute of TechnologyShenzhen 518055China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of TechnologyShenzhen 518055China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China Space Research Institute Austrian Academy of SciencesGrazAustria

Magnetic holes are magnetic depression structures that exist widely in many plasma environments.The magnetic holes with durations of>1 s in the solar wind at Mercury’s orbit have drawn much attention,but the properties of the magnetic holes with shorter durations are still unclear.Here,we investigate the magnetic holes with durations of 0.1-100 s in the upstream region of Mercury’s bow shock based on observations by the MESSENGER(MErcury Surface,Space ENvironment,GEochemistry,and Ranging)spacecraft.They can be divided into two groups according to the distribution of their duration:small-duration magnetic holes(SDMHs,0.6 s).The duration of each group approximately obeys a log-normal distribution with a median of~0.25 s and 3 s,respectively.Approximately 1.7%(32.6%)of the SDMHs(LDMHs)reduce the magnetic field strength by more than 50%.For both groups,some structures have a linear or quasi-linear polarization,whereas others have an elliptical polarization.The magnetic hole events in both groups tend to have a higher rate of occurrence when the interplanetary magnetic field strength is weaker.Their occurrence rates are also affected by Mercury’s foreshock,which can increase(decrease)the occurrence rate of the SDMHs(LDMHs).This finding suggests that Mercury’s foreshock might be one source of the SDMHs and that the foreshock can destroy some LDMHs.These observations suggest that a new group of magnetic holes with durations of<0.6 s exist in the upstream region of Mercury’s bow shock.

关键词： magnetic hole solar wind Mercury foreshock

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Step-over of strike-slip faults and overpressure fluid favor occurrence of foreshocks:Insights from the 1975 Haicheng fore-main-aftershock sequence,China

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Earthquake Research Advances 2024年第1期4卷 36-46页

作者： Xinglin Lei Zhiwei Wang Shengli Ma Changrong He Geological Survey of Japan AISTTsukuba305-8567Japan State Key Laboratory of Earthquake Dynamics Institute of GeologyCEABeijing100029 China

This study analyzed and summarized in detail the spatial and temporal distributions of earthquakes,tidal responses,focal mechanisms,and stress field characteristics for the M 7.3 Haicheng earthquake sequence in February 1975.The foreshocks are related to the main fault and the conjugate faults surrounding the extension step-over in the middle.The initiation timing of the foreshock clusters and the original time of the mainshock were clearly modulated by the Earth's tidal force and coincided with the peak of dilational volumetric tidal strain.As a plausible and testable hypothesis,we proposed a fluid-driven foreshock model,by which all observed seismicity features can be more reasonably interpreted with respect to the results of existing models.Together with some other known examples,the widely existing step-over along strike-slip faults and associated conjugate faults,especially for extensional ones in the presence of deep fluids,favor the occurrence of short-term foreshocks.Although clustered seismicity with characteristics similar to those of the studied case is not a sufficient and necessary condition for large earthquakes to occur under similar tectonic conditions,it undoubtedly has a warning significance for the criticality of the main fault.Subsequent testing would require quantification of true/false positives/negatives.

关键词： Haicheng earthquake Seismogenic fault ETAS foreshock Deep fluid

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Observational evidences of wave excitation and inverse cascade in a distant Earth foreshock region

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Science China Earth Sciences 2019年第4期62卷 619-630页

作者： Jiansen HE Die DUAN Xingyu ZHU Limei YAN Linghua WANG School of Earth and Space Sciences Peking University Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences

The foreshock with nascent plasma turbulence is regarded as a fascinating region to understand basic plasma physical processes, e.g., wave-particle interactions as well as wave-wave couplings. Although there have been plenty of intensive studies on this topic, some key clues about the physical processes still lack observations. A relatively comprehensive case study with some new observations is presented in this work based on the WIND spacecraft observations. In this case, upstream energetic protons were drifting at tens of Alfvén speed with respect to the background plasma protons. When looking at the magnetic wave activities, we find the co-existence of high-frequency(0.1-0.5 Hz) large-amplitude right-hand polarized(RHP) waves and lowfrequency(0.02-0.1 Hz) small-amplitude left-hand polarized(LHP) waves in the spacecraft(SC) frame. The observed anticorrelation between magnetic and velocity fluctuations along with the sunward magnetic field direction indicates that the lowfrequency LHP waves in the SC frame are in fact the sunward upstream RHP Alfvénic waves in the solar wind frame. This new observation corroborates the applicability of theories about plasma non-resonance instability and inverse cascade to the foreshock region, where the downstream high-frequency RHP parent waves are excited by the upstream energetic protons through non-resonance instability and the low-frequency RHP daughter waves are generated by the parent waves due to nonlinear parametric instability. Furthermore, enhanced downstream energetic proton fluxes are inferred to result from scattering of the upstream protons by the nascent turbulent fluctuations. Therefore, some critical clues about the newborn turbulence in the foreshock are provided in this work.

关键词： Solar wind foreshock Wave-particle interaction Parametric instability

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The Tongliao MS5.3 Earthquake and Its foreshock Determination

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Earthquake Research in China 2018年第3期32卷 344-354页

作者： Wang Shubo Zhuoli Getu Li Juan Earthquake Agency of Inner Mongolia Autonomous Region Hohhot 010010China

Taking the 2013 Tongliao MS5. 3 earthquake as a research subject, on the basis of statistical analysis of earthquake sequence using the HypoDD location method and focal mechanism solutions,the paper analyzes and discusses the relationship between the ML4. 4 and MS5. 3 earthquakes. The results show that the Tongliao MS5. 3 earthquake occurred under the background of medium-small earthquakes long-term quiescence and short-term enhancement in the epicentral area. The results of accurate seismic location shows that the Tongliao MS5. 3 earthquake sequence is distributed in the NW direction,extending 10 km,and the ML≥3. 0 aftershocks are concentrated south of the mainshock. The distance between the MS5. 3 mainshock and the ML4. 4 foreshock is about 1. 8 km,with a focal depth of 7. 208 km and 7. 089 km,respectively,their focal location is very close,and may have occurred on the same fault plane. The results of focal mechanism shows that the Tongliao MS5. 3 earthquake is of the strike-slip type,the focal mechanism of aftershocks are disordered,and with time lapse,the type is changed from strike-slip to thrust and normal faulting. The bigger foreshocks had similar focal mechanism and were all normal fault types,which exhibits to some extent,an obvious crustal medium anisotropy in the epicentral area before macroscopic rupturing,as represented by alignment fractures,with stress action enhanced,this"consistency"of seismic precursor regime would gestate the mainshock. According to the characteristics of temporal-spatial distribution of earthquake sequence and similarity of focal mechanism,we judge that the Tongliao MS5. 3 earthquake sequence is a foreshock-mainshock-aftershock type.

关键词： Tongliao M S5.3 earthquake HypoDD location CAP Focal mechanism similarity foreshock determination

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Small-scale ion flux and magnetic field fluctuations in solar wind, foreshock and magnetosheath

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Chinese Physics B 2007年第5期16卷 1477-1487页

作者： N. N. Shevyrev 杜艰 G. N. Z astenker 王赤 P. E. Eiges Space Research Institute Russian Academy of Sciences Profsoyuznaya Street 84/32 117997 Moscow Russia Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Graduate School Chinese Academy of Sciences Beijing 100080 China

We have continued investigation of waves in the regions of undisturbed solar wind, foreshock and magnetosheath. The analysis of ion flux and magnetic field variations with the time interval 1-240s was performed in the regions above. Very large variation in such a time interval can be considered the common feature of the foreshock and magnetosheath. The results of case and statistical studies showed that the level of relative variations of ion flux and magnetic field magnitude in foreshock is about 3 times larger than in undisturbed solar wind. Variations of these parameters in the magnetosheath topologically connected with the quasi-parallel bow shock are about two times larger than those behind the quasi-perpendicular. We also compared the results from Interball-1 data analysis with those from statistical analysis of cluster magnetic field measurements. The magnetic field variations obtained from the different satellite data coincide with each other very well not only in quality but also in quantity.

关键词： magnetosheath foreshock solar wind

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An example of earthquake nucleation of the strong continental earthquakes

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Acta Seismologica Sinica(English Edition) 2001年第2期14卷 225-229页

作者： CHEN Xue-zhong Center of Analysis and Prediction China Seismological Bureau Beijing China Seismological Bureau of Xinjiang Uygur Autonomous Region Ürümqi China

Introduction　　 The study on earthquake nucleation is widely concerned by seismologists in the world. The experimental and theoretical studies indicate that earthquakes should be preceded by quasi-static slip within a nucleation zone (Oh-naka, 1992; Dodge, Beroza, 1995; Dodge, et al, 1996; Ohnaka, Kuwahara, 1990; Yamashita, Ohnaka, 1991). The earthquake nucleation process means a transition from quasi-static to quasi-dynamic rupture process, and it itself is a short-term precursor. Immediate foreshocks are local dynamic instabilities that occur during the transition from the quasi-static to the quasi-dynamic nucleation of the dynamic instability (Ohnaka, 1992). According to the recent theoretical study, immediate foreshocks can be regarded as the localized fractures accompanied by the quasi-static nucleation process of a large earthquake (Shibazaki, Matsu'ura, 1995). Therefore, foreshocks could occur during the nucleation process. The nucleation of earthquakes can be illuminated through analyzing foreshock activity in detail. Detection of the nucleation process by means of a foreshock study is a potential tool for earthquake predic-tion. The nucleation process of Izu peninsula earthquake with M=7.0 on January 14, 1978 is revealed by Ohnaka with foreshock activities. It was observed that the nucleation zone indicated by foreshocks grew at a rate of 1～40 cm/s before reaching a diameter of 10 km. The depths of foreshocks do not change much more, keep within 10 km. Recently, Hurukawa have studied the nucleation process of Off-Etorofu earthquake with MW=7.9 on December 3, 1995. The results show distinctly the nucleation process before the main shock. In the nucleation process, rupture started at the deepest point of the foreshock area, and then propagated to the shallow depth with the apparent ve-locity of 5～20 cm/s (Hurukawa, 1998). Rastogi and Mandal (1998) studied the rupture nucleation process of five Koyna medium-sized main shocks using the time-space patterns of foreshocks. They found that the nucleation zone g

关键词： strong continental earthquake foreshock earthquake nucleation P315.75

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Study on Simulation of foreshock Activity Properties before Strong Earthquake Using Heterogeneous Cellular Automata Models

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International Journal of Geosciences 2014年第3期5卷 274-285页

作者： Meng Li Feng Yang Tao Zhang Earthquake Administration of Xinjiang Uygur Autonomous Region Urumqi China

Three different degrees of heterogeneous fault models are simulated by using 2-D random dynamic cellular automata models for analyzing macroscopic behaviors of seismic activity evolution influenced by heterogeneity of fault structures. The results show that the heterogeneities of fault structures can influence evolution properties of the foreshock activity and rupture process, such as the mediate heterogeneous and less heterogeneous structures, which show relatively higher ASR rates and more significant seismic gaps before main shocks. Besides, stress drop distribution ranges of the foreshock events when approaching a main shock show more homogenous (narrower) than that of the foreshock events far from a main shock. So the heterogeneity of fault structures plays an important role in strong earthquake preparation processes.

关键词： Cellular Automata Model Simulation Heterogeneity foreshock Activity

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How to Identify foreshocks in Seismic Sequences to Predict Strong Earthquakes

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Open Journal of Earthquake Research 2017年第1期6卷 55-71页

作者： Giulio Riga Paolo Balocchi Geologist Independent Researcher Lamezia Terme Italy Geologist Independent Researcher Modena Italy

The time analysis of seismic events preceding several strong earthquakes occurred in recent decades throughout the world, has highlighted some foreshocks’ characteristics, which are helpful for their discrimination compared to other types of events. These features can be identified within the seismic sequence and used as strong events’ precursors. Through the energy release pattern analysis, which precedes any strong earthquakes, in this study we describe some graphical procedures suitable for distinguishing a foreshock from any other type of earthquake. We have broadly divided foreshocks into two classes, depending on their position within the energy release pattern, by describing some relationships between the foreshock’s magnitude and the following earthquake’s. The results obtained show how the energy release pattern of some major earthquakes has distinctive features and repeatability which it is possible to obtain information from in order to perform sufficiently reliable short-term forecasts.

关键词： foreshock Mainshock Aftershock Earthquake Microsequence Hierarchization

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Short-Term Earthquake Forecast with the Seismic Sequence Hierarchization Method

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Open Journal of Earthquake Research 2016年第2期5卷 79-96页

作者： Giulio Riga Paolo Balocchi Geologist Independent Researcher Lamezia Terme Italy Geologist Independent Researcher Modena Italy

All strong earthquakes are preceded by branching structures having different durations whose development scheme is partly largely predictable because it follows a well organized and recognizable pattern. By using a seismic sequence hierarchization method, this study graphically explains the preparation process of an earthquake, called “branching structure”. In addition, criteria apt to distinguish the structures that will produce shocks of average magnitude from strong earthquakes’ will be defined. Based on the temporal oscillations of the magnitude values, we explain the procedure for identifying the developmental stages that characterize the energy accumulation stage of the branching structure, in order to early detect the energy release stage’s trigger point and obtain information on how it will develop over time. The study identifies also some pre-signals (trigger points) of various magnitudes in the energy release stage, which allows us to early predict the foreshocks and mainshock time position. The method we developed constitutes a truly innovative approach for the earthquake forecasting analysis, which dramatically differs from those developed so far, as it considers the structure of the seismic sequence not only as a magnitude values’ oscillation, but also as a sequence of developmental stages that may begin much earlier.

关键词： Branching Structure Earthquake Microsequence Hierarchization foreshock

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