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1.
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
2.
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
3.
The empirical model of the location of the main ionospheric trough (MIT) is developed based on an analysis of data from CHAMP satellite measured at the altitudes of ~350–450 km during 2000–2007; the model is presented in the form of the analytical dependence of the invariant latitude of the trough minimum Φm on the magnetic local time (MLT), the geomagnetic activity, and the geographical longitude for the Northern and Southern Hemispheres. The time-weighted average index Kp(τ), the coefficient of which τ = 0.6 is determined by the requirement of the model minimum deviation from experimental data, is used as an indicator of geomagnetic activity. The model has no limitations, either in local time or geomagnetic activity. However, the initial set of MIT minima mainly contains data dealing with an interval of 16–08 MLT for Kp(τ) < 6; therefore, the model is rather qualitative outside this interval. It is also established that (a) the use of solar local time (SLT) instead of MLT increases the model error no more than by 5–10%; (b) the amplitude of the longitudinal effect at the latitude of MIT minimum in geomagnetic (invariant) coordinates is ten times lower than that in geographical coordinates. 相似文献
4.
M. G. Deminov G. F. Deminova G. A. Zherebtsov O. M. Pirog N. M. Polekh 《Geomagnetism and Aeronomy》2011,51(3):348-355
Results of statistical analysis of the properties of variability of F2-layer maximum parameters (critical frequency foF2 and the height hmF2) in quiet midlatitude ionosphere under low solar activity in the daytime (1000–1500 LT) and nighttime (2200–0300 LT) hours
are presented on the basis of Irkutsk station data for 2007–2008. It is found that the distribution density of δfoF2 could be presented as consisting of two distinctly different normal laws of this distribution, one of which corresponds
to weak (|δfoF2| < 10%) fluctuations in foF2 and the other corresponds to strong (30% > |δfoF2| > 10%) fluctuations. Weak fluctuations in foF2 to a substantial degree are related to ionospheric variability at times less of than 1–3 h and determine the δfoF2 variability in the daytime hours. Strong fluctuations in foF2 are mainly related to day-to-day variability of the ionosphere at a fixed local time, the variability increasing by approximately
a factor of 3 during the transition from day to night and determining the δfoF2 variability in the nighttime hours. The distribution density of ΔhmF2 is close to the normal distribution law. An interpretation of the different character of the distribution densities of δfoF2 and ΔhmF2 is given. 相似文献
5.
Geomagnetism and Aeronomy - A global dynamic model of the F2 layer of the ionosphere GDMF2 is designed to calculate foF2 in both quiet and geomagnetically disturbed conditions. The term... 相似文献
6.
Geomagnetism and Aeronomy - Based on an analysis of data from the midlatitude ionospheric stations, it is found that the P = 0.5(F1 + F81) index is an optimal solar-activity index for the daily... 相似文献
7.
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
8.
A.B. Shvartsburg V.G. Korobeinikov M.G. Deminov A.V. Razmadze 《Planetary and Space Science》1979,27(2):159-163
The non-linear stationary temperature waves (domains) is analysed. The exact analytical solutions of the non-linear equation of the heat conductivity determine the region of existence of such domains and the critical values of plasma parameters, correspond to the increase of the periodical temperature profiles in the plasma. A stationary source of heating (photo-electrons or electric fields) may stimulate the existence of domains, when the power of the source reaches a critical value. Conditions in the F-region of the ionosphere near the equator favour the increase of the domains. 相似文献
9.
V. V. Alpatov V. I. Badin I. A. Grebnev M. G. Deminov D. S. Faermak 《Geomagnetism and Aeronomy》2012,52(6):793-796
The results of a theoretical analysis of the radial distribution of electron temperature T e in the area of heating of the lower ionosphere by intense shortwave radiation are presented. It was established that effective radius r eff of heating at a certain height may differ significantly from the characteristic radius of illumination of the ionosphere (a) by radiation at this height. At the boundary of the heating area (r = r eff ), the characteristic radial scale of T e changes is less than the corresponding scale of changes in the squared amplitude of the radiation electric field, and it is almost independent of the amplitude value; i.e., the formation of a relatively strong T e gradient at such a boundary is a common feature of heating of the lower ionosphere by intense shortwave radiation. 相似文献
10.
Geomagnetism and Aeronomy - Abstract—By comparing the moving 12-month averaged values of the F107 solar radiation flux at a wavelength of 10.7 cm and ionospheric solar activity index T, we... 相似文献