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1.
A new single-station model (SSM) for monthly median values of the ionospheric parameters foF2 and M(3000)F2 has been developed. Fourier analysis provides a tool for decomposing the time-varying ionospheric parameters. The 12–month smoothed sunspot number R
12
was used as an external solar characteristic because of its availability and predictability. However, for the first time, the solar activity is described not only by R
12
, but also by the linear coefficient K
R
representing the tendency of the change of solar activity. A general non-linear approximation of the influence of the solar-cycle characteristics R
12
and K
R
and ionospheric parameters foF2 and M(3000)F2 was accepted. The new SSM is applied to several European stations and its statistical evaluation shows better results than the other two SSMs used in the paper. The approach described in the paper does not contradict the use of different synthetic ionospheric indices (as the T-index, MF2–index); the basic aim is to show only that using one additional new characteristic of the solar-cycle variations, such as K
R
, improves the monthly median model. 相似文献
2.
Agriculture in Bulgaria entered a severe crisis in 1989 following the collapse of the central planning system. Since then it has been going through a transition towards market-based system and a structural transformation from large state cooperatives to smaller privately owned and operated farms and cooperatives. Irrigation, a major water use until recently, has been strongly affected by these processss, and has dropped to a point where less than 15% of the areas equipped for irrigation are actually irrigated. Heavy state investments in the irrigation subsector and its vital importance for the economy make it imperative to up-grade and restructure irrigated agriculture to reflect new forms of land ownership and farming, as well as the current and future organizational patterns of the 相似文献
3.
Pl. Mukhtarov B. Andonov C. Borries D. Pancheva N. Jakowski 《Journal of Atmospheric and Solar》2010,72(2-3):193-205
The present paper focuses on planetary wave type responses of the thermosphere/ionosphere system to forcing from above and below during the Arctic winter of 2005/2006. The forcing from above is described by the sunspot numbers, the solar wind speed, the Bz-component of the IMF and the geomagnetic Kp-index, while the forcing from below, i.e. by upward propagating atmospheric waves, is represented by the SABER/TIMED temperatures. The observed global ionospheric zonally symmetric oscillations with periods of ～9, ～14 and ～24–27 days were approved to be of solar origin. The most persistent ～9-day oscillation is linked to a triad of solar coronal holes distributed roughly 120° apart in solar longitude. The ～18-day westward propagating wave with zonal wavenumber 1, observed in the ionospheric currents (detected by magnetometer data), and in the F-region plasma (foF2 and TEC) could be allocated to a simultaneous 18-day westward propagating planetary wave observed in the stratosphere/mesosphere/lower thermosphere region with large (～70 km) vertical wavelength. 相似文献
4.
Studia Geophysica et Geodaetica - The ionospheric response to geomagnetic storms is usually investigated by considering the variability of the critical frequency of the F2-layer (foF2) or the total... 相似文献
5.
The response of the critical frequency of the ionosphere F2–layer, described by its main Fourier components (daily constant, diurnal and semidiurnal waves) and the lower thermosphere dynamics to the geomagnetic storms in July 1991 and February 1992 is studied. The daily constant displays a negative response, however, the magnitude of reaction depends on the season and latitude. The amplitudes of diurnal and semidiurnal waves increase during a geomagnetic storm, as this enhancement is very strong at high latitudes in winter. The prevailing neutral wind, especially the zonal wind, shows an inclination to decrease during the geomagnetic storm (the effect is more distinct in summer). The amplitudes of diurnal and semidiurnal tides also demonstrate a tendency toward reduction during high geomagnetic activity. 相似文献
6.
We give a new theoretical basis for examination of the presence of the Kerr black hole (KBH) or the Kerr naked singularity
(KNS) in the central engine of different astrophysical objects around which astrophysical jets are typically formed: X-ray
binary systems, gamma ray bursts (GRBs), active galactic nuclei (AGN), etc. 相似文献
7.
Large-scale thermodynamics of the stratosphere and mesosphere during the major stratospheric warming in 2003/2004 总被引：1，自引：0，他引：1
P. Mukhtarov D. Pancheva B. Andonov N.J. Mitchell E. Merzlyakov W. Singer W. Hocking C. Meek A. Manson Y. Murayama 《Journal of Atmospheric and Solar》2007,69(17-18):2338
The stratosphere–mesosphere response to the major sudden stratospheric warming (SSW) in the winter of 2003/2004 has been studied. The UKMO (UK Meteorological Office) data set was used to examine the features of the large-scale thermodynamic anomalies present in the stratosphere of the Northern Hemisphere. The vertical and latitudinal structure of the genuine anomalies, emphasized by removing the UKMO climatology, has been investigated as well. The features of the stratospheric anomalies have been related to the mesospheric ones in measured neutral winds from radars and temperatures from meteor radars (90 km). It was found that the stratospheric warming spread to the lower mesosphere, while cooling occurred in the upper mesosphere, a feature that may be related to the large vertical scales of the stationary planetary waves (SPWs). It was shown also that the beginning of the eastward wind deceleration in the stratosphere–mesosphere system coincided with the maximum amplification of the SPW1 accompanied by short-lived bursts of waves 2 and 3. 相似文献
8.
A. Sh. Mukhtarov F. A. Kadirov V. A. Mamedov 《Izvestiya Physics of the Solid Earth》2010,46(6):524-528
In order to reconstruct the ground surface temperature history (GSTH) in the Kura depression from the data on borehole temperatures,
we selected two thermal logs, which met the requirements of the well temperature inversion into the GSTH. The temperature
gradients measured in these wells varied about 20 K/km, which is typical for the region of study. The borehole temperatures
were inverted into the ground surface temperatures in the past in accordance with the program developed by Po Yu Shen. It
was found that the ground surface temperature had increased by 1–2°C during the last century. The GSTH derived from the well
temperature inversion agrees with the climate temperatures measured at the Ganca meteorological station, which has been operating
since 1873. These results obtained for the Kura depression are consistent also with the results of similar studies in other
regions in the world. 相似文献
9.
On the basis of bispectral analysis applied to the hourly data set of neutral wind measured by meteor radar in the MLT region above Bulgaria it was demonstrated that nonlinear processes are frequently and regularly acting in the mesopause region. They contribute significantly to the short-term tidal variability and are apparently responsible for the observed complicated behavior of the tidal characteristics. A Morlet wavelet transform is proposed as a technique for studying nonstationary signals. By simulated data it was revealed that the Morlet wavelet transform is especially convenient for analyzing signals with: (1) a wide range of dominant frequencies which are localized in different time intervals; (2) amplitude and frequency modulated spectral components, and (3) singular, wave-like events, observed in the neutral wind of the MLT region and connected mainly with large-scale disturbances propagated from below. By applying a Morlet wavelet transform to the hourly values of the amplitudes of diurnal and semidiurnal tides the basic oscillations with periods of planetary waves (1.5/20 days), as well as their development in time, are obtained. A cross-wavelet analysis is used to clarify the relation between the tidal and mean neutral wind variability. The results of bispectral analysis indicate which planetary waves participated in the nonlinear coupling with the atmospheric tides, while the results of cross-wavelet analysis outline their time intervals if these interactions are local. 相似文献
10.
D. Pancheva P. Mukhtarov B. Andonov N.J. Mitchell J.M. Forbes 《Journal of Atmospheric and Solar》2009,71(1):75-87
Part 2 of the present paper is focused on the planetary wave coupling from the stratosphere to the lower thermosphere (30–120 km) during the Arctic winter of 2003/2004. The planetary waves seen in the TIMED/SABER temperature data in the latitudinal range 50°N–50°S are studied in detail. The altitude and latitude structures of the planetary wave (stationary and travelling) clearly indicate that the stratosphere and mesosphere (30–90 km) are coupled by direct vertical propagation of the planetary waves, while the lower thermosphere (above 90–95 km altitude) is only partly connected with the lower levels probably indirectly through in-situ generation of disturbances by the dissipation and breaking of gravity waves filtered by lower atmospheric planetary waves. A peculiar feature of the thermal regime in the lower thermosphere is that it is dominated by zonally symmetric planetary waves. 相似文献