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M. G. Deminov A. V. Belov E. V. Nepomnyashchaya V. N. Obridko 《Geomagnetism and Aeronomy》2018,58(4):501-508
Equations of regression are derived for the intense magnetic storms of 1957?2016. They reflect the nonlinear relation between Dstmin and the effective index of geomagnetic activity Ap(τ) with a timeweighted factor τ. Based on this and on known estimations of the upper limit of the magnetic storm intensity (Dstmin =–2500 nT), the maximal possible value Ap(τ)max ~ 1000 nT is obtained. This makes it possible to obtain initial estimates of the upper limit of variations in some parameters of the thermosphere and ionosphere that are due to geomagnetic activity. It is found, in particular, that the upper limit of an increase in the thermospheric density is seven to eight times larger than for the storm in March 1989, which was the most intense for the entire space era. The maximum possible amplitude of the negative phase of the ionospheric storm in the number density of the F2-layer maximum at midlatitudes is nearly six times higher than for the March 1989 storm. The upper limit of the F2-layer rise in this phase of the ionospheric storm is also considerable. Based on qualitative analysis, it is found that the F2-layer maximum in daytime hours at midlatitudes for these limiting conditions is not pronounced and even may be unresolved in the experiment, i.e., above the F1-layer maximum, the electron number density may smoothly decrease with height up to the upper boundary of the plasmasphere. 相似文献
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Geomagnetism and Aeronomy - Analysis of the features of the form of low solar cycles 23 and 24 for the solar-activity indices (F is the solar radio flux at a wavelength of 10.7 cm, Rz and Ri are... 相似文献
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The relevance of the occurrence rate and location of CME events to two main systems (giant and supergiant) of the large-scale solar magnetic field structure has been investigated. The clustering of CME events and solar flares toward the neutral line of the global field system (neutral line of the source surface field) corroborates the finding by Hundhausen that CME locations track the heliomagnetic equator. A good correlation has been revealed between the CME occurrence rate and variations of the index of the effective solar multipole, that characterizes the typical scale of the global solar magnetic field. The CME rate exhibits sharp jumps/decreases when the index of the effective solar multipole passes through n=4. The observations of X-ray 'blow-out' effects have been analyzed as probable manifestations of CMEs on the disk and have been compared with the large-scale magnetic field structure. As shown by the analysis, the X-ray arcades straddle the neutral line and occur, or at least tend to occur, where the neutral line exhibits a sharp bend. A conclusion is made that CME events are caused by interaction of two large-scale field systems, one of them (the global field system) determining the location of CMEs and another (the system of closed magnetic fields) their occurrence rate. 相似文献
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Based on the known forecast of solar cycle 25 amplitude (Rz max ≈ 50), the first assessments of the shape and amplitude of this cycle in the index of solar activity F10.7 (the magnitude of solar radio flux at the 10.7 cm wavelength) are given. It has been found that (F10.7)max ≈ 115, which means that it is the lowest solar cycle ever encountered in the history of regular ionospheric measurements. For this reason, many ionospheric parameters for cycle 25, including the F2-layer peak height and critical frequency (hmF2 and foF2), will be extremely low. For example, at middle latitudes, typical foF2 values will not exceed 8–10 MHz, which makes ionospheric heating ineffective in the area of upper hybrid resonance at frequencies higher than 10 MHz. The density of the atmosphere will also be extremely low, which significantly extends the lifetime of low-orbit satellites. The probability of F-spread will be increased, especially during night hours. 相似文献
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Using the data of Moscow station for 1975–1985, the seasonal features in the dependence of the spread-F probability P near midnight on the levels of solar and geomagnetic activity have been analyzed. It has been found that the P dependence on solar activity is most substantial in winter and fall, the P dependence on geomagnetic activity is maximal during equinoxes, and the P dependence on solar activity prevails in summer but is much weaker than in winter and fall. Based on the qualitative analysis of the known mechanisms of the midlatitude spread-F, the regression equation, which shows the P dependence on the solar activity level and thermospheric parameters (temperature and density) at a fixed average level of geomagnetic activity, has been obtained. In this equation the character of the seasonal changes in P is determined by the thermospheric parameters, the relative contribution of which depends on solar activity. The found dependence of the character of the P seasonal variations on the solar activity level has been interpreted based on this equation. 相似文献
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Geomagnetism and Aeronomy - Characteristics of changes in the solar activity indices (the flux of the solar radio emission at a wavelength of 10.7 cm F and the new version of the relative sunspot... 相似文献
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