A model of the impact of solar proton events on the ionic and gaseous composition of the mesosphere     

Yu. E. Ozolin  I. L. Karol’  E. V. Rozanov  T. A. Egorova 《Izvestiya Atmospheric and Oceanic Physics》2009,45(6):737-750

A one-dimensional ionic-photochemical model of the gaseous composition of the atmosphere that describes the formation of the D layer of the ionosphere is presented. Based on this model, the vertical profiles of the concentration of electrons and ions in the D layer of the ionosphere were calculated, as were the vertical distributions of minor gaseous constituents in the atmosphere up to a height of 86 km for undisturbed conditions and after a powerful solar proton events (SPE) at the end of October 2003. The calculations showed that SPEs significantly increase NO_x in the mesosphere of polar latitudes. In the lower mesosphere of polar caps, the NO_x mixing ratio increases by 20–50 ppb; in the upper mesosphere it increases by 100 ppb and more. High NO_x levels in zones of their formation can be retained for several weeks, producing a long-term but comparatively small ozone decrease in the lower mesosphere. The main ozone decrease is caused by a short-term HO_x increase after SPEs and is also of a short-term character in the conditions of the illuminated mesosphere. After the SPE in October 2003, model calculations yield an ozone concentration decrease by 40% in the middle and upper mesosphere at 75 ° S and by 70% at the same heights at 70 ° N. The results of modeling NO_x and O₃ changes after the SPE in October 2003 agree well with the data of satellite measurements. The changes in minor gases of the mesosphere after the SPE obtained in the model with parameterized sources of HO_x and NO_x are compared with their changes obtained in the complete ionic-photochemical model. The changes in HO_x, NO_x, and O₃ coincide rather well, whereas the changes in ClO noticeably differ, especially in the lower mesosphere. Thus, at a height of about 60 km, the parameterized photochemical model underestimated twofold the ClO formation after the SPE.  相似文献   

Mafic Intrusions of ca. 2400 Ма Large Igneous Province in the Belomorian Mobile Belt: First Baddeleyite U–Pb ID-TIMS Data     

Stepanova  A. V.  Salnikova  E. B.  Samsonov  A. V.  Egorova  S. V.  Stepanov  V. S. 《Doklady Earth Sciences》2020,493(2):617-620

Doklady Earth Sciences - U–Pb ID-TIMS dating of igneous baddeleyite from metamorphosed coronitic gabbronorites in the сentral part of the Belomorian mobile belt, Fennoscandian shield...  相似文献   

土地利用影响下的岩溶地下水水化学变化特征   总被引：10，自引：2，他引：8  

郭芳  姜光辉  夏青  李科 《中国岩溶》2007,26(3):212-218

为了进一步探讨土地利用方式与地下水水质的关系,在湖南湘西峒河流域采集了包括地下水和地表水的131个样品,在室内进行简分析或全分析,并现场测量了水样的p H、温度和电导率。依据土地利用方式和污染来源将峒河流域的岩溶地下水划分为3种类型: 第一类,不受耕地和居民点影响的岩溶地下水;第二类,受耕地但不受居民点影响的岩溶地下水;第三类,受居民点影响的岩溶地下水。将三类岩溶地下水中K+ 、Na+ 、Cl- 、SO2-4 和NO-3 的浓度从大到小放在一个坐标系中比较,结果显示第三类岩溶地下水的5种离子浓度最大,第二类中等,第一类最低,表明土地利用方式对岩溶地下水水质影响明显。在空间分布上,岩溶地下水离子浓度具有东部和东南、西北较高的特点,表现为一些泉水遭到明显的污染,与这些地方土地利用类型以水田、旱地和农村居民点为主,即与农耕施肥和生活垃圾排放有关。虽然居民点或耕地等土地利用类型目前还没有致使地下水水质超过饮用水标准,但是流域内的饮水安全问题不容忽视。   相似文献   

Evaluation of a gravel transport sensor for bed load measurements in natural flows     

Athanasios N. 《国际泥沙研究》2009,24(1):1-15

A recent acoustic instrument （Gravel Transport Sensor, GTS） was tested for predicting sediment transport rate （bed load rate） in gravel bed streams. The GTS operation is based on the particle collision theory of submerged obstacles in fluids. When particles collide with the GTS cylinder their momentum is recorded in the form of ping rates. The GTS is attractive for further consideration here because of its potential to provide continuous unattended local bed load measurements, especially in areas found in streams that access may be difficult under extreme conditions. Laboratory experiments coupled with numerical simulations for the same flow conditions were performed in order to determine the conditions under which particles of different size will hit the GTS cylinder and be able to register a ping rate. The GTS was able to detect the number of particles with diameter in the range of 15.9 to 25.4 mm, with reasonable accuracy, if the applied Shields effective stress τ＊e = τ＊ - τ＊cr was in the range of 0.006 to 0.015. A drawback of the tested prototype GTS, however, was that it exerted increased resistance on the incoming particles. The added drag effects increased the overall resistance that was exerted by the flow on particles and thus increased the likelihood that particles will rest in the ambient region of the cylinder instead of hitting it. Numerical simulation of the flow around the GTS cylinder revealed that changing the prototype geometry from cylindrical to ellipsoid or rhomboid will increase the likelihood of the particles hitting the instrument under the same flow conditions failed by the original tested GTS cylinder.  相似文献   

Effects of solar and geomagnetic activity in long-term variations in the ionospheric parameters of the auroral zone in 1963–1986     

V. Ya. Vovk  L. V. Egorova 《Geomagnetism and Aeronomy》2010,50(4):461-466

A stable linear relation between foF2 and W with a correlation coefficient of 0.68–0.96 has been revealed as a result of a joint analysis of the foF2 critical frequencies and the virtual minimal heights (h’F) obtained from the data of vertical sounding (VS) of the ionosphere at Dixon Island auroral station, Wolf numbers (W), and PC geomagnetic index from 1963 to 1986. A significant linear relation exists between foF2 and the PC index with a correlation coefficient of r = 0.18–0.67. The correlation between the PC index and W is low in winter and autumn and is r = 0.50 and 0.74 at a significance level of ss = 0.96–0.99 in spring and summer. When the correlation between PC and foF2 is analyzed, it is necessary to consider the effect of solar activity (SA) on both parameters. The multiple correlation coefficients between these parameters have been calculated with regard to the effect of W. They were R = 0.75−0.98; however, the standardized regression coefficients β _W and β _PC indicated that W and PC considerably and insignificantly affect multiple correlation with foF2, respectively, and this effect depends on the season and time of day. It has been detected that the cyclic variations in foF2 and h’F are asymmetric. The amplitudes of these parameters in cycle 20 are smaller than in cycle 21.  相似文献   

Thermomechanical Modeling of the Formation of Multi-Сhamber Intrusions for Identifying the Relationship of Plutonic Metamorphism with Gabbro-Diorite Massifs of Western Sangilen,Tuva, Russia     

Polyansky  O. P.  Izokh  A. E.  Semenov  A. N.  Selyatitskii  A. Yu.  Shelepaev  R. A.  Egorova  V. V. 《Geotectonics》2021,55(1):1-19

Geotectonics - For the first time, a thermomechanical model of a system of multilevel magma chambers above a mantle heat source has been developed to explain the formation mechanisms of intrusive...  相似文献   

Collisional mafic magmatism of the fold-thrust belts framing southern Siberia (Western Sangilen,southeastern Tuva)     

R.A. Shelepaev  V.V. Egorova  A.E. Izokh  R. Seltmann 《Russian Geology and Geophysics》2018,59(5):525-540

We consider geochemical features of mafic magmatism manifested during the evolution of a complex nappe-folded structure in Western Sangilen, resulted from the Cambrian-Ordovician collisional tectogenesis. There are abundant ultramafic-mafic and mafic associations of different types in this region: layered low-Ti low-alkali ultramafic-mafic intrusions, high-Ti medium-alkali gabbroids, gabbro-monzodiorite intrusions, and alkali basalts. Isotope-geochronological data showed that these complexes formed over a wide time interval, from 570 to 440 Ma. At this time, the geodynamic setting in Western Sangilen changed from an island-arc one via a collision one to an intercontinental rift setting. At the early and late stages of the evolution of Western Sangilen, the geochemical features of mafites were typical of their geodynamic settings. The properties of mafites that formed synchronously with the collision are of particular interest. The studies have shown that the chemical composition of collisional mafites of Western Sangilen changed with time. They became richer in alkalies, titanium, and incompatible elements. This fact indicates a change in the type of mantle source from suprasubductional in the Cambrian to enriched deeper-level one in the Ordovician.  相似文献   

The conditions of formation of sapphire and zircon in the areas of alkali-basaltoid volcanism in Central Vietnam     

A.E. Izokh  S.Z. Smirnov  V.V. Egorova  Tran Tuan Anh  S.V. Kovyazin  Ngo Thi Phuong  V.V. Kalinina 《Russian Geology and Geophysics》2010,51(7):719-733

Study of the chemical composition of clinopyroxene and garnet megacrysts from the Dak Nong sapphire deposit and model calculations have shown that megacrysts originated from the crystallization of alkali basaltoid magma in a deep-seated intermediate chamber at 14–15 kbar, which is close to the Moho depth (50 km) in this part of southeastern Asia. The chamber was a source of heat and CO₂ fluids for the generation of crustal syenitic melts producing sapphires and zircons. The formation conditions of sapphires and zircons are significantly different. The presence of jadeite inclusions in placer zircons points to high pressures during their crystallization, which is confirmed by the ubiquitous decrepitation of CO₂-rich melt inclusions. Sapphires crystallized from iron-rich syenitic melt in the shallower Earth’s crust horizons with the participation of CO₂ and carbonate–H₂O–CO₂ fluids. The subsequent eruptions of alkali basalts favored the transportation of garnet and pyroxene megacrysts as well as sapphire and zircon xenocrysts to the surface. It is shown that sapphire deposits can be produced only during multistage basaltic volcanism with deep-seated intermediate chambers in the regions with thick continental crust. The widespread megacryst mineral assemblage (clinopyroxene, garnet, sanidine, ilmenite) and the presence of placer zircon megacrysts can be used as indicators for sapphire prospecting.  相似文献