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F.T. Berkey V.M. Driatskiy K. Henriksen B. Hultqvist D.H. Jelly T.I. Shchuka A. Theander J. Ylindemi 《Planetary and Space Science》1974,22(2):255-307
Sixty auroral absorption substorms (30 in IQSY and 30 in IASY) have been analysed on the basis of riometer-recordings taken at some 40 stations distributed over auroral, subauroral and polar cap latitudes. Synoptic maps showing isoabsorption curves have been produced every 15 min (sometimes every 5 min) of the 60 substorms; 705 maps altogether.Some of the results of the analysis are as follows.Initiation of a substorm most frequently occurs near midnight but may occur anywhere between early evening and late morning. The time of onset becomes earlier and the latitude of onset moves equatorward as the level of magnetic activity increases.The longitude expansion velocities are contained in the range 0.7–7 km/sec except for a few extreme values which exceed 20 km/sec.The auroral absorption eastward expansion velocity is smaller than the corresponding velocity of the boundary of the region of activation of the visual aurora after break up by a factor .The expansion velocity corresponds, in general, to drift velocities of electrons of energies in the range 50–300 keV but, for the extreme speeds, electron energies around 1 MeV are needed.Expansion of the absorption in the westward direction was seen in about half of the substorms studied. In about half of these, expansion along the auroral oval could be indentified, but in almost all of these cases some expansion in the auroral zone latitudes was also seen. In about an equal number of events, expansion was confined primarily to the auroral zone.The velocity of the westward expansion was about 1 km/sec along the auroral oval (i.e. approximately equal with the speed of the westward travelling surge) but about 2 km/sec along the auroral zone.The meridional expansion velocities found agree well with those measured for visual aurora (? 1 km/sec).The variability of the behaviour of different substorms is very large. To illuminate this the following may be mentioned, in addition to what has been stated above about the statistics.Although the absorption maximum practically always moves eastward from the initiation region, exceptions have been seen in which the maximum started moving west and in a later phase went eastward.Sometimes the absorption maximum stays in the injection area or very close to it, although in most cases it moves eastward into the dayside. In extreme eases it has been found to move more than 270° in the eastward direction.There are auroral absorption substorms in which injection seems to take place in more than one area simultaneously.The observations cannot all be understood in terms of gradient and curvature drift of electrons from a small area of injection only. A broad intrusion of hot plasma from the tail into the inner magnetosphere seems to be needed.No strong dependence of particle precipitation on the illumination of the upper ionosphere by sunlight was seen. The results do, therefore, not support the hypothesis of Brice and Lucas (1971) that cold plasma density increases, originating in the ionosphere, significantly increase the precipitation rate of energetic trapped particles. 相似文献
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Demidov A. B. Gagarin V. I. Eremeeva E. V. Artemiev V. A. Polukhin A. A. Shchuka S. A. Grigoriev A. V. Khrapko A. N. Flint M. V. 《Oceanology》2021,61(5):645-661
Oceanology - Spatial and vertical variability of primary production (PP) and Chl a were studied in the framework of the 76th cruise of R/V Akademik Mstislav Keldysh to the Kara Sea from July 7 to... 相似文献
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E. G. Arashkevich A. V. Drits A. F. Pasternak M. V. Flint A. B. Demidov A. B. Amelina M. D. Kravchishina I. N. Sukhanova S. A. Shchuka 《Oceanology》2018,58(3):381-395
Sampling was conducted along the quasi meridional transect at 130° E from the Lena River estuary to northern deep-sea regions of the Laptev Sea in September 2015. The latitudinal zonality and the impact of river runoff are manifested in the temperature and salinity distribution, concentration of particulate organic matter, and the structure of plankton communities. The differences in the chl a concentration and primary production along the transect are insignificant. The feeding rate of mesozooplankton herbivores was assessed by a fluorescence technique. The total consumption of phytoplankton biomass and primary production are estimated based on the feeding rate, abundance of zooplankton species, and their diel migrations. The daily grazing impact of zooplankton on phytoplankton biomass increases from 2% on the inner shelf to 3% on the mid-shelf, 5% on the outer shelf, and 10% in the deep-sea part of the basin. The consumption of primary production also increases: 1, 4.5, 5.7, and 13.9%, respectively. In the fall, the consumption of phytoplankton does not compensate the energy demands for respiration. The latitudinal zonality of the Laptev Sea appears not only in the hydrophysical water parameters and the structure of plankton communities, but also in their functional characteristics. 相似文献
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The specific features of the upwelling in the southeastern Baltic have been studied by comparing the field observations and numerical simulations. The upwelling registered in October 2005 (when a gale caused by a northeastern wind with a velocity of 15 m/s continued for about three days after a period of relatively calm weather during which the thermohaline structure was in the state close to the summer one) has been considered in detail. The gale caused a decrease in the temperature by approximately 4°C in the along-shore belt with a width of about 8 km in the region with depths of about 25 m located at a distance of approximately 8 km from the shore. The changes in the thermohaline structure that originated as a result of this gale were simulated using a 3D numerical model based on the Princeton Ocean Model (POM). This made it possible not only to consider the variability of the thermohaline fields at the observation region but also to study a rather wide region and to consider the field of velocity in addition to the fields of temperature and salinity. Subsequently, the numerical model made it possible to estimate the upwelling effect during cooling of the upper layer, which was more intense than the effect of turbulent mixing by an order of magnitude. It was confirmed that the specific features of the upwelling spatial structure depend on the geographic position of the upwelling observation region and on the velocity and duration of the wind that causes the upwelling. 相似文献
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Kremenetskiy V. V. Nedospasov A. A. Shchuka S. A. Shchuka A. S. Zamyatin I. A. Bondar A. V. 《Oceanology》2021,61(6):786-790
Oceanology - During cruise 81 of the R/V Akademik Mstislav Keldysh comprehensive studies of the Kara Sea were carried out over sill separating the central spur of the St. Anna Trough and the Novaya... 相似文献
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A. I. Chava A. A. Udalov A. A. Vedenin M. I. Simakov S. A. Shchuka V. O. Mokievsky 《Oceanology》2017,57(1):144-153
Benthic fauna in Tsivolki Bay (Novaya Zemlya Archipelago, Kara Sea) has been studied during the voyage of the R/V Professor Shtokman in 2013 and 2014. A peculiar feature of the bay is the presence of the Serp i Molot glacier in its inner part, which determines the extremely high content of suspended particles in the water column. The bay is divided into three parts: the inner part (close to the glacier), the middle basin, and the outer slope. These parts are separated from each other by several rises. Benthic communities changed gradually from the inner part of the bay towards the outer slope. Three communities were described from the data of nine grab stations (26 samples). The apex of the bay is occupied by the depleted community dominated by the isopod Saduria sabini and the bivalve Yoldiella lenticula, which can successfully survive the increased mineral sedimentation. In the middle basin, it is replaced by the transitional community with Ennucula tenuis and Portlandia arctica being the main dominants. Finally, the outer slope is inhabited by the community typical for the open parts of the Kara Sea. It is dominated by Astarte crenata, Ophiacantha bidentata, and Ophiopleura borealis. The main reason for macrobenthic distribution in the studied region is the content of mineral particles in the water column and bottom layers. 相似文献
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Oceanology - It is believed that the waters of rivers flowing into the Kara Sea (predominantly discharge of the Yenisei and Ob rivers) can propagate to the east, penetrating the Laptev Sea with the... 相似文献
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Miroshnikov A. Yu. Flint M. V. Dubinina E. O. Asadulin En. E. Shchuka S. A. Usacheva A. A. 《Doklady Earth Sciences》2018,483(2):1582-1586
Doklady Earth Sciences - This paper reports on the results of radiation monitoring of bottom sediments in Yenisei Gulf for the period from 1995 to 2016. Clear positive trends in changing the... 相似文献