An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.
Abstract Case and statistical studies have been performed to investigate hot flow anomalies (HFAs) with large flow deflections using data from the Cluster‐C1 spacecraft from 2003 to 2009. We have selected 87 events with V y or V z in GSE coordinates larger than 200 km s −1 . Observations of these HFAs indicate a “location‐dependent deflection”: V y or V z deflect to a positive value when the event is located in the positive Y or Z side relative to the subsolar point and to a negative value when it is located in the negative Y or Z side relative to the subsolar point. The amplitude of the deflection increases with increasing distance in Y or Z direction. The decrease in V x at the event center is larger when the location is closer to the Sun‐Earth line. The location‐dependent deflection might be due to a near‐specular reflection of ions at the Earth's bow shock. The HFAs studied in this paper are close to the bow shock with the distance of the event location to the bow shock ranging from 0.03 to 3.51 R E , which might cause the reflected ions to remain as a coherent near‐specular reflected beam.
Hydraulic positioning systems are widely used in the areas of transportation, earth moving equipment, aircraft, and industry machinery with heavy duty applications. In these systems, nonlinear friction as a typical disturbance, is difficult to model and will influence the system performance. In this paper, we investigate the robust fractional-order PID (FOPID) control for position tracking of a fluid power ElectroHydraulic Actuator (EHA) system which is one type of hydraulic positioning systems. Firstly, the EHA model with friction force uncertainty is built. Then, the FOPID controller which is tuned by the grey wolf optimizer (GWO) is proposed. In the goal function for GWO, we take the uncertainty limits of friction force into consideration. The FOPID parameters are obtained by minimizing the goal function. The effectiveness of the proposed control approach is validated by simulation results in Matlab.
Abstract The existence of shocklets, a kind of solitary structure, has been demonstrated in the Earth's foreshock regions for decades. Their formation and evolution are believed to be controlled by ions. However, the detailed behavior of ions at them has not been well investigated observationally yet. Here, we investigate a shocklet observed by the Magnetospheric Multiscale mission in the Earth's foreshock. Analysis of ion observations reveals that the solar wind (SW) ions are bunched in gyrophase space when interacting with the whistler precursor of the shocklet, suggesting the occurrence of cyclotron resonance between them. A more detailed examination suggests that the cyclotron resonance induces a net energy flow from the whistler precursor to the SW ions. Thus, the observations presented here indicate that the cyclotron resonance between shocklet whistler precursors and the SW ions could provide a mechanism for shocklet dissipation and SW ion energization.
Abstract Ionospheric outflow has been shown to be a dominant ion source of Earth's magnetosphere. However, most studies in the literature are about ionospheric outflow injected into the nightside magnetosphere. We still know little about ionospheric outflow injected into the dayside magnetosphere and its further energization after it enters the magnetosphere. Here, with data from Magnetospheric Multiscale mission, we report direct observations of the modulation of dayside ionospheric outflow ions by ultralow frequency (ULF) waves. The observations indicate that the modulation is mass dependent, which demonstrates the possibility of using ULF waves as a mass spectrometer to identify ion species. Moreover, the measurement suggests that polarization drift may play a role in O + modulation, which may lead to a true acceleration and even nonadiabatic behavior of O + . This interaction scenario can work throughout the whole magnetosphere and impact upon the plasma environment and dynamics.
The northwest block of Y2 reservoir is a bottom water reservoir,Its exploitation effect is very poor.The study on the water cut rising characteristic have an important role for improving the development of the reservoir effect.It fund that the actual water rising velocity is far outweigh the relative permeability calculation theory water cut up speed,through the contrast with the actual water cut curve and relative permeability calculation theoretic water cut curve.The single well water cut curve is mainly for convex.According to the change of yield and water cut,the single well water cut curve is divided into three types to discusse.And the reason of each type is analyzed.Finally,on the basis of the analysis of the single well water cut up,the reason of the water cut of the reservoir as a whole to be a step-like is analyzed.The reservoir bottom water coning is serious.The remaining oil is mainly concentrated between the injection-production patterns.Therefore,the horizontal well technology for tapping potentialities of the reservoir can be considered.
Abstract The staged fracturing and microseismic monitoring techniques are used for horizontal well stimulation in the Fuling shale gas field. From the analysis of the microseismic data, most of the wells are well stimulated. However, there are still some zones which are not broken thoroughly between adjacent two clusters. When decreasing the cluster space in the adjacent well, this bad phenomenon can be avoided. The cluster space is the key factor for the multi-stage hydraulic fracturing. How to choose it? Two things must be concerned, one is the fracture geometry, and the other is the induced stress field between each two adjacent fractures. A three-dimensional (3D) multi-fracture propagation model was developed. The mixed boundary element method was used to describe the propagation of the 3D fractures. The fluid flow in a fracture was modeled by the lubrication equation and the Navier-Stokes equations. The fluid flow in the wellbore was considered as the one-dimensional flow. Newton-Raphson and Picard iterative methods were used to discrete the 3D multi-fracture propagation model. Based on the geomechanics parameters of the Fuling shale reservoir, the fracture geometry and stress interference between each two adjacent fractures are studied. Numerical simulations are carried out to study the influences of the cluster arrangements, fluid displacement and viscosity, bedding plane, shale anisotropic, etc. on the fractures geometry, net pressure inside the fractures and induced stress fields, which reveals the fracture propagation interference mechanism of multi-stage hydraulic fracturing. An optimized cluster space exits for a specific well. 20-25 meter cluster space is recommended for the shale gas formation with well-developed bedding planes, and 25-35 meter recommended for the shale gas formation with non-developed bedding planes. The results are used for the on-site perforation cluster spacing optimization in about ten shale gas wells in Fuling shale gas field, the microseismic signals are full in the shale formation between two adjacent fractures. The 3D multi-fracture propagation model are established, and the fractures geometry and induced stress fields are studied, which can help to optimize the perforating cluster space and hydraulic fracturing parameters.
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