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911.
B.J. Adekoya V.U. Chukwuma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):274-286
Classification and quantification of the interplanetary structures causing intense geomagnetic storms (Dst?≤??100?nT) that occurred during 1997–2016 are studied. The subject of this consists of solar wind parameters of seventy-three intense storms that are associated with the southward interplanetary magnetic field. About 30.14% of the storms were driven by a combination of the sheath and ejecta (S?+?E), magnetic clouds (MC) and sheath field (S) are 26% each, 10.96% by combined sheath and MCs (S?+?C), while 5.48% of the storms were driven by ejecta (E) alone. Therefore, we want to aver that for storms driven by: (1) S?+?E. The Bz is high (≥10?nT), high density (ρ) (>10?N/cm3), high plasma beta (β) (>0.8), and unspecified (i.e. high or low) structure of the plasma temperature (T) and the flow speed (V); (2) MC. The Bz is ≥10?nT, low temperature (T?≤?400,000?K), low ρ (≤10?N/cm3), high V (≥450?km), and low β (≤0.8); (3) The structures of S?+?C are similar to that of MC except that the V is low (V?≤?450?km); (4) S. The Bz is high, low T, high ρ, unspecified V, and low β; and (5) E. Is when the structures are directly opposite of the one driven by MCs except for high V. Although, westward ring current indicates intense storms, but the large intensity of geomagnetic storms is determined by the intense nature of the electric field strength and the Bz. Therefore, great storms (i.e. Dst?≤??200?nT) are manifestation of high electric field strength (≥13?mV/m). 相似文献
912.
Jiansheng Yu Kai Tan Caihong Zhang Bin Zhao Dongzhen Wang Qi Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(2):840-856
A total of more than 260 continuous stations and 2000 campaign stations from the Crustal Movement Observation Network of China (CMONOC) project, covering the Chinese mainland and its surrounding areas during the period of 1998–2018, are processed using the Bernese Global Navigation Satellite System (GNSS) software via a state-of-the-art method. We obtain the coordinate time series of all the stations given in the reference frame ITRF2014, estimate the coseismic deformation, and remove outliers. Lastly, we present the latest, most complete, and most accurate contemporary horizontal velocity field with respect to the stable Eurasian plate, irrespective of the postseismic deformations. This study shows that the signal of tectonic movement in Western China is stronger than that in Eastern China particularly in the Tibetan Plateau, with a rate of 18–32?mm/a. Moreover, the signal decays sharply from south to north. However, North China and South China move coherently to the ESE direction mostly at a rate of 4–10?mm/a and have not experienced any abrupt velocity gradients in their interiors. Meanwhile, Northeast China has the lowest velocity of only 2–4?mm/a in addition to the coastal areas that have slightly larger velocities. The densified and continuous observation of GNSS stations are of great significance to the study of the present-day crustal movement and tectonic deformation characteristics of the Chinese mainland. This would help to provide better constraints on the kinematics and dynamics of the region. 相似文献
913.
914.
A. Maier S. Krauss W. Hausleitner O. Baur 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
In the framework of satellite-only gravity field modeling, satellite laser ranging (SLR) data is typically exploited to recover long-wavelength features. This contribution provides a detailed discussion of the SLR component of GOCO02S, the latest release of combined models within the GOCO series. Over a period of five years (January 2006 to December 2010), observations to LAGEOS-1, LAGEOS-2, Ajisai, Stella, and Starlette were analyzed. We conducted a series of closed-loop simulations and found that estimating monthly sets of spherical harmonic coefficients beyond degree five leads to exceedingly ill-posed normal equation systems. Therefore, we adopted degree five as the spectral resolution for real data analysis. We compared our monthly coefficient estimates of degree two with SLR and Gravity Recovery and Climate Experiment (GRACE) time series provided by the Center for Space Research (CSR) at Austin, Texas. Significant deviations in C20 were noted between SLR and GRACE; the agreement is better for the non-zonal coefficients. Fitting sinusoids together with a linear trend to our C20 time series yielded a rate of (−1.75 ± 0.6) × 10−11/yr; this drift is equivalent to a geoid change from pole to equator of 0.35 ± 0.12 mm/yr or an apparent Greenland mass loss of 178.5 ± 61.2 km3/yr. The mean of all monthly solutions, averaged over the five-year period, served as input for the satellite-only model GOCO02S. The contribution of SLR to the combined gravity field model is highest for C20, and hence is essential for the determination of the Earth’s oblateness. 相似文献
915.
916.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(9):2167-2171
In this study, the impact of Earth’s magnetic field on total electron content (TEC) was studied by using statistical multiple linear regression model and co-integration method. TEC values were measured over the Turkey-Istanbul (ista) station using date of global positioning system (GPS), and the magnetic field components of the Earth were measured from Boğaziçi University, Kandilli Observatory and Earthquake Research Institute, Geomagnetic observatory Istanbul (ISK) station. This examination has been carried out during the dates of March 14–19, 2015 covering the dates of March 17–18, 2015 known in the literature as St. Patrick's Day geomagnetic storm. The three days before the storm (March 14–16) were named as quiet days, whereas the other days (March 17–19) were named as disturbed days after which the two periods were examined separately. It was observed as a result of the examination that the x-component (south-north direction) of the magnetic field had a negative impact on TEC on quiet days, whereas the impact was positive on disturbed days. However, the y-component (east–west direction) of the magnetic field had an inverse relationship of the x-component on the quiet and disturbed days. In addition, it was deduced that the impact coefficient of the x and y-component of the magnetic field was higher on disturbed days in comparison with those on quiet days. The correlation coefficient between the TEC and the components of the Earth’s magnetic field was 0.11 on quiet days and 0.95 on disturbed days. Therefore, it can be stated that the relationship of the TEC values with the geomagnetic field are higher on disturbed days. 相似文献
917.
918.
V.A. Kotov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3385-3389
Time variations of the magnetic field of the Sun, seen as a star (the data 1968–2018, with more than 27 thousand daily measurements of the solar mean magnetic field), allowed to specify the rotation period of the gravitating solar mass: 27.027(6)?days, synodic. This indicates a presumably unknown physical connection between motions of the Sun and the Earth: in the course of a year our star accomplishes nearly 27 half-revolutions, while the planet itself performs an identical number of its spinnings during one complete axial revolution of the Sun. True origin of this strange Sun–Earth resonance is unknown, but it is supposed the phenomenon might be caused by slight coherent perturbations of gravity within the solar system. 相似文献
919.
This paper examines the Shock/Shock Interactions (SSI) between the body and wing of aircraft in supersonic flows. The body is simplified to a flat wedge and the wing is assumed to be a sharp wing. The theoretical spatial dimension reduction method, which transforms the 3D problem into a 2D one, is used to analyze the SSI between the body and wing. The temperature and pressure behind the Mach stem induced by the wing and body are obtained, and the wave configurations in the corner are determined. Numerical validations are conducted by solving the inviscid Euler equations in 3D with a Non-oscillatory and Non-free-parameters Dissipative (NND) finite difference scheme. Good agreements between the theoretical and numerical results are obtained. Additionally, the effects of the wedge angle and sweep angle on wave configurations and flow field are considered numerically and theoretically. The influences of wedge angle are significant, whereas the effects of sweep angle on wave configurations are negligible. This paper provides useful information for the design and thermal protection of aircraft in supersonic and hypersonic flows. 相似文献
920.
远场涡流检测技术因检测深度深和检测结果可靠性高等诸多优点适合飞机多层金属铆接构件的快速检测。针对飞机铆接件铆钉孔沿边隐藏裂纹的原位检测,建立了多层金属铆接构件隐藏缺陷平面远场涡流检测有限元模型,对激励线圈内径、磁路结构以及屏蔽阻尼进行了仿真优化,研制了激励线圈和检测线圈均带组合屏蔽结构的传感器,采用激励-检测线圈环绕铆钉旋转扫描的方式,研究多层金属铆接构件铆钉孔沿边隐藏裂纹信号特征。仿真与试验结果表明:罐形磁芯聚磁效果是柱形磁芯的1.85倍,采用铝+铜组合屏蔽罩能够将远场区提前10 mm,检测线圈位于缺陷正上方时,检测信号的幅值和相位存在极大值,且极大值随着缺陷埋深的增加逐渐下降,研究成果可望用于指导飞机多层金属铆接构件的工程检测实践。 相似文献