Winter Anomaly in the Critical Frequency of the <Emphasis Type="Italic">E</Emphasis>-Layer in the Nighttime Polar Cap     

M. G. Deminov  G. F. Deminova 《Geomagnetism and Aeronomy》2018,58(1):62-69

With the medians of the E-layer critical frequency foE measured at Resolute Bay and Casey ionospheric stations located in the polar caps of the Northern and Southern Hemispheres, it is found that these medians are higher at the nighttime hours (2100–0300 LT) in the local winter than in local summer. For Resolute Bay station, which is located above the Arctic Circle, the latter means that the foE median is higher at polar night than at polar day. Thus, the effect of a winter anomaly in the foE median in the nighttime polar cap is detected. The amplitude of that anomaly (the ratio of the local winter foE values to local summer values) could reach 15–20% and 10–15% for Resolute Bay and Casey stations, respectively. It is assumed that the winter anomaly in the foE median in the nighttime polar cap is caused by the winter–summer asymmetry in the accelerated electron energy fluxes precipitating into this region.  相似文献   

Regular Variations of Intensity of the Westward Auroral Electrojet according to the Geomagnetic <Emphasis Type="Italic">AL</Emphasis> Index     

G. F. Krymskii  G. A. Makarov 《Geomagnetism and Aeronomy》2018,58(3):332-337

Diurnal and seasonal variations of the geomagnetic AL index are studied. It is found in disturbed days that the mode of AL diurnal variation depends on the angle between the Sun–Earth line prolongation in the direction towards the magnetotail and the plane of geomagnetic equator; on quiet days, AL depends on the angle of attack between the geomagnetic axis and the Earth–Sun line. Seasonal AL variations are characterized by annual variations with summer maximum and semiannual variations with equinoctial maxima. It is shown that the semiannual AL variations can be described by a simplified model of plasma convection in the magnetotail based on a plasma electron cooling mechanism.  相似文献   

Formation Mechanisms of the Spring–Autumn Asymmetry of the Midlatitudinal <Emphasis Type="Italic">NmF</Emphasis>2 under Daytime Quiet Geomagnetic Conditions at Low Solar Activity     

A. V. Pavlov  N. M. Pavlova 《Geomagnetism and Aeronomy》2018,58(3):383-393

Formation mechanism of the spring–autumn asymmetry of the F2-layer peak electron number density of the midlatitudinal ionosphere, NmF2, under daytime quiet geomagnetic conditions at low solar activity are studied. We used the ionospheric parameters measured by the ionosonde and incoherent scatter radar at Millstone Hill on March 3, 2007, March 29, 2007, September 12, 2007, and September 18, 1984. The altitudinal profiles of the electron density and temperature were calculated for the studied conditions using a one-dimensional, nonstationary, ionosphere–plasmasphere theoretical model for middle geomagnetic latitudes. The study has shown that there are two main factors contributing to the formation of the observed spring–autumn asymmetry of NmF2: first, the spring–autumn variations of the plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity, and, second, the difference between the composition of the neutral atmosphere under the spring and autumn conditions at the same values of the universal time and the ionospheric F2-layer peak altitude. The seasonal variations of the rate of O⁺(⁴S) ion production, which are associated with chemical reactions with the participation of the electronically excited ions of atomic oxygen, does not significantly affect the studied NmF2 asymmetry. The difference in the degree of influence of O⁺(⁴S) ion reactions with vibrationally excited N₂ and O₂ on NmF2 under spring and autumn conditions does not significantly change the spring–autumn asymmetry of NmF2.  相似文献   

Characteristics of the Energetic Electron Precipitation and Magnetospheric Conditions in 1994     

G.?A.?BazilevskayaEmail author  M.?S.?Kalinin  M.?B.?Krainev  V.?S.?Makhmutov  A.?K.?Svirzhevskaya  N.?S.?Svirzhevsky  Yu.?I.?Stozhkov  B.?B.?Gvozdevsky 《Geomagnetism and Aeronomy》2018,58(4):483-492

The problem of the rapid depletion and saturation of the Earth’s outer radiation belt with energetic electrons is one of the central problems in the physics of the magnetosphere. The precipitation into the atmosphere and the escape of electrons from the magnetosphere are competing reasons for the depletion of the radiation belt. Long-term measurements of energetic electron precipitation (EEP) in the atmosphere in the experiment of the Lebedev Physical Institute (LPI) can be used to study the relative role of these phenomena. High fluence values of relativistic electrons in the outer belt is a necessary condition for EEP observation; however, the relation of the EEP rate to the condition of the belt is ambiguous, which is shown by the example of observations in 1994.  相似文献   

Experimental Studies of the Dynamic Interaction between Model Channel Forms and Flow     

V. S. Borovkov  Yu. V. Bryanskaya  A. V. Ostyakova 《Water Resources》2018,45(2):169-173

Interaction between water flow and ridge bedforms has been studied. The results of experimental studies of velocity distribution over ridge bedforms in a hydraulic laboratory flume are given. The distribution of pressure along the contour of a rigid model ridge, determined in an aerodynamic canal, is also given.  相似文献   

Field Simulation of Cadmium Pollution of a Freshwater Body     

D. N. Gar’kusha  Yu. A. Fedorov  T. V. Knyazeva  N. S. Tambieva 《Water Resources》2018,45(5):746-756

An experiment in mesocosms installed in a fish-rearing pond was used to adequately simulate the character of self-purification, migration, and the redistribution of cadmium and its chemical forms in major components of a freshwater ecosystem, into which this chemical is imported in concentrations far in excess of its MAC. The major portion of the imported cadmium was found to be removed from the water mass within a few days, mostly, as a component of particulate matter settling onto the bed, including dead plankton remains, as ion-exchange cadmium forms adsorbed by suspension (37%), and as forms associated with ferromanganese oxides (41%). The rate of cadmium removal from the water mass is determined both by the amount of particulate matter settling onto the bed and the efficiency of cadmium sorption by it, depending on the acid–alkaline and redox conditions in the water body.  相似文献   

Groundwater Resources and Their Role in Water Supply to Crimea     

R. G. Dzhamalov  F. B. Egorov  T. I. Safronova 《Water Resources》2018,45(6):839-845

The processes of formation and distribution of the resources of fresh groundwater and surface water in the territory of Crimea Peninsula are considered. Water availability in the natural–historic and administrative regions of the republic is characterized. The proportions between different categories of groundwater resources are shown with their role in water supply to Crimea taken into account. The presentday development of groundwater resources is analyzed and the possible increase in water consumption meeting geoecological requirements is substantiated.  相似文献   

The Shiveluch Volcanic Massif,Kamchatka: Stages in the Evolution of a Magmatic System: Results of Geochronological and Thermobarogeochemical Studies     

M. M. Pevzner  M. L. Tolstykh  A. D. Babansky 《Journal of Volcanology and Seismology》2018,12(4):242-251

It is shown that Shiveluch, which consists of several volcanic edifices that stand in one area and in part overlie each other, is a long-lived volcanic massif with a complex structure. The available data on the morphology of the edifice, age, rock compositions, primary melts, and types of eruptive activity were used to identify structurally-temporal units (STUs) in the Shiveluch volcanic massif. It was found that the generation of different-age STUs was due to the activity of at least four magma chambers with different parameters. The durations of the individual chambers were determined. The activities of these chambers were initiated and came to an end nearly instantaneously because of major collapse episodes in the edifice of the massif due to high-magnitude earthquakes.  相似文献   

Geodynamic and Seismotectonic Activity in Eastern Tibet in the 21st Century     

Tuo Shen  E. A. Rogozhin 《Seismic Instruments》2018,54(4):461-478

At the beginning of the 21st century, a series of great earthquakes were recorded in northeastern Tibet, along the periphery of the Bayan Hara lithospheric block. An earthquake with M_S = 8.1 occurred within the East Kunlun fault zone in the Kunlun Mountains, which caused an extended surface rupture with left-lateral strike slip. An earthquake with M_S = 8 occurred in Wenchuan (China) on May 12, 2008, giving rise to an extended overthrust along the Lunmanshan fault zone. An earthquake with M_S = 7.1 occurred in Yushu (China) on April 14, 2010; its epicenter was on the Grazze–Yushu–Funchuoshan fault; a left-lateral strikeslip offset was observed on the surface. An earthquake with M_S = 7 occurred in the vicinity of Lushan on April 20, 2013; its epicenter was within the Lunmanshan fault zone, 103 km southwest of the zone of the catastrophic Wenchuan earthquake. An earthquake with M_S = 8.2 occurred in Nepal on April 25, 2015. Based on the CSN seismic catalog, the energy of all earthquakes in eastern Tibet at the end of the 20th and beginning of the 21st centuries was estimated. It was found that Tibet was seismically quiet from 1980 to 2000. The beginning of the 21st century has been marked by seismic activation with earthquake sources migrating southward to surround the Bayan Hara lithospheric block from every quarter. Therefore, this block can be regarded as one of the most seismically active regions of China.  相似文献   

Space Research: Gravitoinertial Instruments     

O. N. Andreev  V. B. Dubovskoi  I. I. Kalinnikov  A. V. Kalyuzhny  V. I. Leontyev  A. B. Manukin  S. S. Obydennikov  V. G. Pshenyanik 《Seismic Instruments》2018,54(5):557-561

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