A Statistical Study on the Geomagnetically Induced Current Events Driven by Earth-directed Full-Halo Coronal Mass Ejections

Solar activities can cause the anomalies of electric power transmission systems, especially, for an extra-long distance transmission system. Using the data of coronal mass ejection (CME) from SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph), and the data of the geomagnetically induced current (GIC) and geomagnetic storm from the North China Electric Power University and Finnish Meteorological Institute, respectively, we analyze some important observational features and physical properties of the earth-directed halo CMEs associated with the GIC events. After classifying the observed halo CMEs according to their symmetry, it is found that the halo CMEs associated with GIC events are mainly the 3 types: completely symmetric, brightness-asymmetric, and outline-asymmetric. The geomagnetically induced current events driven by the three different types of halo CMEs have different characteristics in the intensity, duration, and period. We ?nd that the brightness-asymmetric halo CMEs are most likely to cause the major damage to the transmission systems. And that the geomagnetically induced current has also a good correlation with the time variation of geomagnetic ?eld.     

Seismic constraints on rock damaging related to a failing mountain peak: the Hochvogel,Allgäu

Large rock slope failures play a pivotal role in long-term landscape evolution and are a major concern in land use planning and hazard aspects. While the failure phase and the time immediately prior to failure are increasingly well studied, the nature of the preparation phase remains enigmatic. This knowledge gap is due, to a large degree, to difficulties associated with instrumenting high mountain terrain and the local nature of classic monitoring methods, which does not allow integral observation of large rock volumes. Here, we analyse data from a small network of up to seven seismic sensors installed during July–October 2018 (with 43 days of data loss) at the summit of the Hochvogel, a 2592 m high Alpine peak. We develop proxy time series indicative of cyclic and progressive changes of the summit. Modal analysis, horizontal-to-vertical spectral ratio data and end-member modelling analysis reveal diurnal cycles of increasing and decreasing coupling stiffness of a 260,000 m³ large, instable rock volume, due to thermal forcing. Relative seismic wave velocity changes also indicate diurnal accumulation and release of stress within the rock mass. At longer time scales, there is a systematic superimposed pattern of stress increased over multiple days and episodic stress release within a few days, expressed in an increased emission of short seismic pulses indicative of rock cracking. Our data provide essential first order information on the development of large-scale slope instabilities towards catastrophic failure. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

从重力异常探讨威宁地区深部地质构造

从1：20万布格重力异常分离出来的剩余重力异常和水平梯度重力异常为主要研究对象,结合威宁地区的地质、物化探、遥感资料,揭示该区深部存在8条断裂,火山机构1个,基性-超基性侵入岩体1个。     

Ecohydrological change mechanism of a rainfed revegetation ecosystem at southeastern edge of Tengger desert,Northwest China

Study is made on a 45 km-long artificial ecosystem without irrigation in Tengger desert on the basis of long-term ecological monitoring and ecohydrological fundamentals.Changes in water allocation, utilization, cycle and balance patterns in more than 40-year evolution of the soil-plant system are analyzed. The formation of a drought horizon in shrub rhizosphere and its effect, ecohydrological function of the crust and its effect on the soil-plant system change are discussed. Driven by water self-regulation and water stress, the soil-plant system is going to develop towards the steppe desert to ensure more effective use and optimum collocation of water resource.     

Calculation of the Model of Coesite Inclusions and Analysis of Their Retrometamorphic Paths

The process and path of retrometamorphism of coesite have great significance to our understanding of the P-T tracks of the exhumation of ultrahigh-pressure metamorphic rocks. Most of the coesites in the eclogite from Shima, Anhui Province, the Dabie Mountains, China, are found degraded to quartz partly or wholly, with ruptures occurring in the shells, outside which include the coesite and quartz. According to the microscopic observation, the sample of coesite inclusion is composed of garnet, quartz and coesite, based on which we have built a three-shelled composite sphere model to compute the transition of coesite. Based on the crystal growth formulas and pressure conditions of the ruptures in the garnet, we have calculated the radius of the quartz sphere, which depends on temperature, and eventually drawn the different retrometamorphic paths for different retrometamorphism rates.     

Molecular lines from protoplanetary nebulae: observations with ALMA

Planetary nebulae (PNe) are formed in a very fast process. In just about 1000 years, the nebula evolves from a spherical and slowly expanding AGB envelope to a PN, with usually axial symmetry and high axial velocities. Molecular lines are known to probe most of the nebular material in young PNe and protoplanetary nebulae (PPNe), and are therefore very useful to study such an impressive evolution. Many quantitative results on these objects have been so obtained, including general structure, total mass and density distribution, kinetic temperatures, velocity fields, etc. Existing observations probe both the gas accelerated by post-AGB shocks and the quiescent components. But the study of crucial regions to understand PN formation (recently shocked shells, regions heated by the stellar UV and inner rotating disks) requires observations at higher frequency and with better spatial resolution.