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611.
Geomagnetism and Aeronomy - The solar activity index and parameters of the spatial distribution of sunspots are known to be related. Using these relationships, we propose interrelated... 相似文献
612.
Weak‐anisotropy approximation for P‐wave reflection coefficient at the boundary between two tilted transversely isotropic media
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Existing and commonly used in industry nowadays, closed‐form approximations for a P‐wave reflection coefficient in transversely isotropic media are restricted to cases of a vertical and a horizontal transverse isotropy. However, field observations confirm the widespread presence of rock beds and fracture sets tilted with respect to a reflection boundary. These situations can be described by means of the transverse isotropy with an arbitrary orientation of the symmetry axis, known as tilted transversely isotropic media. In order to study the influence of the anisotropy parameters and the orientation of the symmetry axis on P‐wave reflection amplitudes, a linearised 3D P‐wave reflection coefficient at a planar weak‐contrast interface separating two weakly anisotropic tilted tranversely isotropic half‐spaces is derived. The approximation is a function of the incidence phase angle, the anisotropy parameters, and symmetry axes tilt and azimuth angles in both media above and below the interface. The expression takes the form of the well‐known amplitude‐versus‐offset “Shuey‐type” equation and confirms that the influence of the tilt and the azimuth of the symmetry axis on the P‐wave reflection coefficient even for a weakly anisotropic medium is strong and cannot be neglected. There are no assumptions made on the symmetry‐axis orientation angles in both half‐spaces above and below the interface. The proposed approximation can be used for inversion for the model parameters, including the orientation of the symmetry axes. Obtained amplitude‐versus‐offset attributes converge to well‐known approximations for vertical and horizontal transverse isotropic media derived by Rüger in corresponding limits. Comparison with numerical solution demonstrates good accuracy. 相似文献
613.
N. V. Ivanov Yu. A. Kopytenko E. D. Tereshchenko P. E. Tereshchenko 《Geomagnetism and Aeronomy》2017,57(6):752-760
The paper presents the results of studies of the resonance structures of the background electromagnetic noise spectrum obtained in a series of experiments in the autumn of 2012 in Karelia. The experiments are unique because the background noise was detected at stations spaced by a distance much less than the doubled effective waveguide height (about 50 km) in a region close to the main ionospheric trough, the structure and position of which were determined based on radiotomographic data. It is shown that the dimensions of the ionospheric local region, which affects both the generation of spectral resonance structures in particular and the propagation of electromagnetic waves in the considered range in general, depend significantly on the variation of ionospheric parameters in regions with strong horizontal inhomogeneity. 相似文献
614.
Two important sources of information about sunspots in the Maunder minimum are the Spörer catalog (Spörer, 1889) and observations of the Paris observatory (Ribes and Nesme-Ribes, 1993), which cover in total the last quarter of the 17th and the first two decades of the 18th century. These data, in particular, contain information about sunspot latitudes. As we showed in (Ivanov et al., 2011; Ivanov and Miletsky, 2016), dispersions of sunspot latitude distributions are tightly related to sunspot indices, and we can estimate the level of solar activity in the past using a method which is not based on direct calculation of sunspots and weakly affected by loss of observational data. The latitude distributions of sunspots in the time of transition from the Maunder minimum to the regular regime of solar activity proved to be wide enough. It gives evidences in favor of, first, not very low cycle no.–3 (1712–1723) with the Wolf number in maximum W = 100 ± 50, and, second, nonzero activity in the maximum of cycle no.–4 (1700–1711) W = 60 ± 45. Therefore, the latitude distributions in the end of the Maunder minimum are in better agreement with the traditional Wolf numbers and new revisited indices of activity SN and GN (Clette et al., 2014; Svalgaard and Schatten, 2016) than with the GSN (Hoyt and Schatten, 1998); the latter provide much lower level of activity in this epoch. 相似文献
615.
It is proposed to determined minimums of the 11-year solar cycles based on a minimal flux of the large-scale open solar magnetic field. The minimal fluxes before the finished cycle 23 (Carrington rotation CR 1904) and the started cycle 24 (CR 2054, April 2007) were equal to 1.8 × 1022 and 1.2 × 1022 μs, respectively. The long-term tendency toward an approach to a deep minimum of solar activity is confirmed. On the assumption that magnetic flux variations from minimums to maximums are proportional to each other, the anticipated value of the maximal Wolf number during cycle 24 is estimated as W max = 80. 相似文献
616.
Intersector disbalance of the large-scale open solar magnetic field fluxes,active and passive boundaries,and solar-terrestrial extrastorms 总被引:1,自引:1,他引:0
The dynamics (from rotation to rotation) of the absolute values of the large-scale open solar magnetic field fluxes in the four-sector field structure has been considered for the first time, using CRs 2032–2035 in July–October 2005 as examples. An important role of the ratio of the fluxes at the eastern and western sector boundaries (Φ E /Φ W ) is confirmed. As in the cases of the two-sector structure, Φ E /Φ W > 1 is typical of active rigidly corotating boundaries with intense sunspot formation, flares, and interplanetary and geomagnetic disturbances. A remarkable property of the considered structure was the presence of a rapidly increasing flux in an initially narrow sector and the flux interaction with a stable rigidly corotating sector in the zone of the main active longitudes, which caused an unexpectedly strong geoeffective long-range action of flares near the corresponding active boundary. 相似文献
617.
Astronomy Letters - The Gnevyshev—Waldmeier rule relating the lifetimes of sunspot groups and their areas has been verified on an interval of ≈140 years, which exceeds the one used by... 相似文献
618.
We present the results of numerical modeling of the influence of water exchange through the Kerch Strait on the stationary
motions in the Azov Sea. We use a three-dimensional nonlinear numerical model to perform the analysis of extreme deviations
of the sea level and the surface and deep-water currents depending on the direction and velocity of constant wind with and
without regard for the water exchange through the strait. It is shown that the influence of water exchange with the Black
Sea leads to the increase in the maximum deviations of the sea level and the velocities of stationary currents. Thus, in particular,
it is shown that, for a wind velocity of 10 m/sec, the maximum values of the surge and current velocities in the presence
of the strait are higher than in the absence of the strait by 36 and 42%, respectively. In this case, the highest current
velocities are induced by the south wind. 相似文献
619.
A. S. Savvichev E. E. Zakharova E. F. Veslopolova I. I. Rusanov A. Yu. Lein M. V. Ivanov 《Oceanology》2010,50(6):893-908
The results of microbiological, biogeochemical, and isotope geochemical studies in the Kara Sea are described. The samples
for these studies were obtained during the 54th voyage of the research vessel Akademik Mstislav Keldysh in September 2007. The studied area covered the northern, central, and southwestern parts of the Kara Sea and the Gulf of
Ob. The quantitative characteristics of the total bacterial population and the activity of the microbial processes in the
water column and bottom sediments were obtained. The total population of the bacterioplankton (BP) varied from 250000 cells/ml
in the northern water area to 3000000 cells/ml in the Gulf of Ob. The BP population depended on the content of the water suspension.
The net BP production was minimal in the central water area, amounting to 0.15–0.2 μg C/(l day), and maximal (0.5–0.75 μg
C/(l day)) in the Gulf of Ob. The organic material at the majority of the stations in the Ob transect predominantly contained
light carbon isotopes (−28.0 to −30.18‰) of terrigenous origin. The methane content in the surface water layer varied from
0.18 to 2.0 μl CH4/l, and the methane oxidation rate changed in the range of 0.1–100 nl CH4/(l day). The methane concentration in the upper sediment layer varied from 30 to 300 μl CH4/dm3; the rate of the methanogenesis was 44 to 500 nl CH4/(dm3 day) and that of the methane oxidation, 30 to 2000 nl CH4/(dm3 day). The rate of the sulfate reduction varied from 4 to 184 μg S/(dm3 day). 相似文献
620.
K. G. Ivanov 《Geomagnetism and Aeronomy》2010,50(1):1-14
The effectiveness of the series of powerful heliospheric storms, originated during the decline phase of cycle 23 owing to
the superconcentration of the open field photospheric sources in the main zone of active longitudes, has been studied. The
geoeffectiveness of the storm of July 16—27, 2004, was closely related to the origination of the four-sector structure and
depended on the destabilization of two activity centers weakly and strongly geoeffective with ARs 10649 and 10652. The first
center was localized in one of the new sectors; the second center, in the western surroundings of the zone of active longitudes.
The departure of coronal mass ejections from AR 10649 was substantially hindered: they were completely absent after the series
of powerful X-ray flares, and a rare phenomenon of “sunquake” was observed: shock waves did not reach the Earth in spite of
its favorable position. The Earth was strongly shielded by new sector boundaries from coronal ejections from AR 10652 with
a gradual weakening and disappearance of this region, as a result of which the cascade of three near-Earth storms with an
increasing power and Ap, indices of 52, 154, and 186 originated. Rare phenomena in AR 10649 and the cascade of solar—terrestrial heliospheric storms
made the storm of July 16— 27 a unique phenomenon in cycle 23, and a short-term prediction of its geoeffectiveness was impossible. 相似文献