Dependence of D-Region Perturbations of the Midlatitude Ionosphere on the Spectral Composition of the X-Ray Radiation of Solar Flares According to Experimental Data     

Gavrilov  B. G.  Poklad  Yu. V.  Ryakhovsky  I. A.  Ermak  V. M. 《Geomagnetism and Aeronomy》2022,62(1-2):98-103

Geomagnetism and Aeronomy - An experimental study was made of the dependence of the electron-density perturbations in the D?regions of the midlatitude ionosphere during solar flares on the...  相似文献   

The State and Dynamics of the Ionosphere from Synchronous Records of ULF/VLF and HF/VHF Radio Signals at Geophysical Observatory “Mikhnevo”     

Ryakhovskii  I. A.  Gavrilov  B. G.  Poklad  Yu. V.  Bekker  S. Z.  Ermak  V. M. 《Izvestiya Physics of the Solid Earth》2021,57(5):718-730

Izvestiya, Physics of the Solid Earth - Abstract—Studying the spatiotemporal dynamics of the disturbances in the atmosphere, upper, and lower ionosphere requires integrated investigation of...  相似文献   

Surface abundances of light elements for a large sample of early B-type stars – IV. The magnesium abundance in 52 stars – a test of metallicity     

L. S. Lyubimkov  S. I. Rostopchin  T. M. Rachkovskaya  D. B. Poklad  D. L. Lambert 《Monthly notices of the Royal Astronomical Society》2005,358(1):193-201

From high-resolution spectra a non-local thermodynamic equilibrium analysis of the Mg  ii 4481.2-Å  feature is implemented for 52 early and medium local B stars on the main sequence (MS). The influence of the neighbouring line Al  iii 4479.9-Å  is considered. The magnesium abundance is determined; it is found that  log ɛ(Mg) = 7.67 ± 0.21  on average. It is shown that uncertainties in the microturbulent parameter V_t are the main source of errors in  log ɛ(Mg)  . When using 36 stars with the most reliable V_t values derived from O  ii and N  ii lines, we obtain the mean abundance  log ɛ(Mg) = 7.59 ± 0.15  . The latter value is precisely confirmed for several hot B stars from an analysis of the Mg  ii 7877-Å  weak line. The derived abundance  log ɛ(Mg) = 7.59 ± 0.15  is in excellent agreement with the solar magnesium abundance  log ɛ_⊙ (Mg) = 7.55 ± 0.02  , as well as with the proto-Sun abundance  log ɛ _ps (Mg) = 7.62 ± 0.02  . Thus, it is confirmed that the Sun and the B-type MS stars in our neighbourhood have the same metallicity.  相似文献   

The cool giant HD 77361—a super Li-rich star     

L. S. Lyubimkov  B. M. Kaminsky  V. G. Metlov  Ya. V. Pavlenko  D. B. Poklad  T. M. Rachkovskaya 《Astronomy Letters》2015,41(12):809-823

  相似文献   

Determining the effective temperatures of G- and K-type giants and supergiants based on observed photometric indices     

L. S. Lyubimkov  D. B. Poklad 《Kinematics and Physics of Celestial Bodies》2014,30(5):244-254

A method for determining the effective temperature T _eff of G- and K-type giants and supergiants is proposed. The method is based on the use of two photometric indices free from the interstellar absorption influence: the Q index in the UBV photometric system and the [c ₁] index in the uvby system. Empirical relations between the T _eff values found for nearby and bright G- and K-type giants and supergiants with the use of the infrared fluxes method (IRFM), on the one hand, and the observed Q and [c ₁] indices for these stars, on the other hand, are plotted. A systematic discrepancy between the dependences of T _eff on Q for the stars with standard and reduced metallicities is found. Approximating the plotted dependences with second-order polynomials, one can obtain a relatively simple and a rather accurate method for determining the T _eff value in the range of 3800 ≤ T ≤ 5100 K (based on the Q index) or 4900 ≤ T _eff ≤ 5500 K (based on the [c ₁] index).  相似文献   

The Red Giants EK Eri and OU And as Probable Descendents of Ap-stars: A Search for Abundance Anomalies     

Lyubimkov  L. S.  Korotin  S. A.  Petrov  D. V.  Poklad  D. B.  Kudryavtsev  D. O.  Baklanova  D. N. 《Astrophysics》2022,65(1):53-74

Astrophysics - The red giants EK Eri and OU And, with magnetic fields Bmax=99 and 41 G, respectively, which presumably are descendents of magnetic Ap-stars, are studied. Their fundamental...  相似文献   

The chromium and titanium abundances in the atmospheres of A, F, and G supergiants in the solar neighborhood     

D. B. Poklad 《Bulletin of the Crimean Astrophysical Observatory》2013,109(1):48-53

The abundances of two chemical elements of the iron group, viz., Cr and Ti, were determined by their high-resolution spectra for 22 A, F, and G supergiants in the solar neighborhood (within 700 pc). The titanium and chromium abundances were obtained using the Cr II and Ti II lines. The average chromium abundance of log?(Cr) = 5.70 ± 0.13 within the error limit corresponds to the solar abundance of log?_⊙(Cr) = 5.64. The average titanium abundance of log?(Ti) = 4.89 ± 0.10 within the error limit is very close to the solar abundance of log?_⊙(Ti) = 4.95. The average Cr and Ti abundances may be indicative of the fact that the average metallicity of young closely located stars is identical to that of the Sun.  相似文献   

Estimate of Variations in the Parameters of the Midlatitude Lower Ionosphere Caused by the Solar Flare of September 10, 2017     

Gavrilov  B. G.  Ermak  V. M.  Poklad  Yu. V.  Ryakhovskii  I. A. 《Geomagnetism and Aeronomy》2019,59(5):587-592

Geomagnetism and Aeronomy - Changes in the state of the D and E ionospheric regions lead to variations in the amplitude-phase characteristics of VLF radio signals. The existing theoretical and...  相似文献   

Spatiotemporal distributions of the electron density in the ionosphere by records of the total electron content and phase of VLF radio signals     

B. G. Gavrilov  Yu. I. Zetser  A. N. Lyakhov  Yu. V. Poklad  I. A. Ryakhovskii 《Geomagnetism and Aeronomy》2017,57(4):461-470

Features of the structure and dynamics of the ionospheric plasma are studied in a comparison the ionospheric total electron content measurements with the phase and amplitude measurements of VLF–LF radio signals on global and regional paths. The ionospheric structure over Europe is reconstructed. The spatiotemporal dynamics of moving ionospheric disturbances under conditions of a powerful geomagnetic storm of March 17, 2015, is examined based on the reconstruction results. Analysis of the phase variation of VLF radio signals, together with the TEC measurement data, is not only an additional tool in the study of the dynamics of ionospheric disturbances; it also makes it possible to estimate electron density disturbances in different ionospheric layers.  相似文献   

Active Experiments in the Ionosphere at Altitudes of 140–360 km. Optical Observations Results Reanalysis     

Zetser  J. I.  Poklad  Yu. V.  Erlandson  R. E. 《Izvestiya Physics of the Solid Earth》2021,57(5):745-760

Izvestiya, Physics of the Solid Earth - Abstract—Dynamics of complex plasma structures, that drive precipitation and current systems into the ionosphere, produce a multitude of physical and...  相似文献