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Volume 65, Nº 3 (2025)
Articles
OBSERVATION, THEORETICAL CALCULATION AND ANALYSIS OF THE SOLAR FLARE ON MAY 11, 2012
Resumo
Solar flare of May 11, 2012 was observed on two spectrographs of the Astronomical Institute of the Czech Academy of Sciences – a multichannel flare spectrograph and a horizontal setup for solar research. After processing the spectra, integral emission fluxes in the hydrogen, helium and calcium lines were determined. Within the framework of the heated gas model, a theoretical calculation of the plasma parameters was performed taking into account the physical conditions in the chromosphere, including self-absorption in the spectral lines. A comparison of six lines at once made it possible to reconstruct the temperature, density and spatial structure of the emitting gas with a high degree of confidence. At the same time, a search for quasi-periodic pulsations in this solar flare was carried out, which showed the absence of such in almost all spectral ranges. An exception is the detection of pulsations in the images of the chromosphere on the spectrograph slit in the Hα line with a period of 30 s.
Geomagnetizm i aeronomiya. 2025;65(3):307-313
307-313
FORECASTING THE PROBABILITY AND MAGNITUDE OF SOLAR PROTON EVENTS USING FLARES AND EJECTIONS DATA
Resumo
The paper studies various characteristics of solar flares and coronal mass ejections that led or did not lead to the registration of solar proton events near the Earth for the period from 1996 to 2023. A detailed catalog of events was compiled, regression dependences of the parameters of solar sources and proton flux enhancements near the Earth were obtained. A new “proton index” of the event was proposed, and calculations were made of the probability of solar proton events and expected fluxes of particles with different energies. Longitudinal distributions of various parameters characterizing proton flux enhancements were also obtained. The established patterns will form the basis of an empirical model that allows estimating the probability of high-energy particle arrival at the Earth and the expected levels and times of registering the maxima of increases in fluxes of protons with energies >10 and >100 MeV.
Geomagnetizm i aeronomiya. 2025;65(3):314-323
314-323
FORECAST ESTIMATION OF GALACTIC COSMIC RAY MODULATION IN THE 25TH SOLAR CYCLE
Resumo
The difference in the shape of the maxima of galactic cosmic rays (GCR) fluxes for positive (A > 0, even–odd cycle minima) and negative (A < 0, odd–even cycle minima) polarities of the solar dipole magnetic field is well known. For A > 0, a flat GCR maximum is observed, while for A < 0, a sharp one. This difference is associated with the influence of the drift mechanism of GCR propagation in the global magnetic field of the heliosphere, the proxy of which can be considered the polar (dipole) magnetic field of the Sun (Bpole). A homogeneous series of GCR data has been available since 1957, while Bpole observations have been conducted only since 1976. Using the example of odd (21st, 23rd and 25th) and even (22nd and 24th) cycles for which Bpole and GCR observations are available, we investigate the hypothesis that changes in the Bpole value and sign determine the main trends in the development of the entire modulation cycle. Traditionally, the beginning of the 11-year cycle in the long-term GCR modulation is associated with the minimum number of sunspots Rz, but the growth of Rz does not reflect all physical processes on the Sun capable of modulating GCR in the heliosphere. We select the maximum GCR intensity at 10 GV as the beginning of the modulation cycle (zero on the time scale) and then compare the count rate of the Moscow neutron monitor, the Bpole value, and the number of sunspots (Rz) using the superposition of epochs method. With such a choice of zero, the difference in the time profiles of GCRs in even and odd cycles is clearly visible. With a decrease in the Bpole module, the GCR fluxes decrease, the convective transport mechanism prevails, and the effect of drift transport is not visible (there is no clear division into even and odd cycles). With an increase in the Bpole module, the GCR fluxes grow, the diffusion mechanism of GCR transport prevails, which is helped or hindered by the drift mechanism (at A > 0 or at A < 0). The GCR fluxes remain constant at Bpole ~ const. The spot activity Rz is asymmetrical relative to the moment of polarity reversal (Bpole = 0), it is early in even and late in odd cycles. The discovered trends allow us to qualitatively predict the corridor of possible changes in Bpole and GCR fluxes in the decline phase of the 25th cycle and in the minimum of 25–26 cycles, as well as to make an epignostic forecast based on observations of GCR and Rz of possible Bpole values in 1957–1976 (the end of the 19th and the entire 20th cycle).
Geomagnetizm i aeronomiya. 2025;65(3):324-334
324-334
RELATIONSHIPS BETWEEN SOLAR ACTIVITY INDICES IN DIFFERENT TIME INTERVALS
Resumo
The article presents the results of the analysis of long-term changes in the relationship between solar activity indices for 1953−2023. For this purpose, the annual moving averages of the F10, F30, MgII, Ri and T indices were used – the solar radio emission fluxes at wavelengths of 10.7 and 30 cm, the ratio of the central part to the flanks in the magnesium emission band of 276–284 nm, the international sunspot number and the ionospheric index, which is determined from ionospheric data as an analogue of the sunspot number. It has been found that the entire measurement period can be divided into the intervals 1953−1980, 1981−2012 and 2013−2023, in which the relationships between the solar activity indices differ distinctly. In the interval 1953−1980, these relationships are stable, i.e. there is practically no linear time trend in the dependence of one solar activity index on another. In the interval 2013−2023, such trends are usually significant. The boundaries of these intervals (1980 and 2013) approximately correspond to the maxima of the first and last solar cycles in the decreasing activity regime, when the large-scale solar magnetic field and the solar cycle height decrease over time. Therefore, the relationships between the solar activity indices, including the relationships between the ionospheric index and solar indices provide additional information on changes in the solar cycle regimes and can serve as one of the characteristics of changes in these regimes.
Geomagnetizm i aeronomiya. 2025;65(3):335-342
335-342
TRENDS IN PARAMETERS OF THE F LAYER AND THEIR POSSIBLE CAUSES
Resumo
The results of determination of the long-term trends in the parameters of the ionospheric F2 layer (critical frequency, height, total electron content, and slab thickness) are considered. It is shown that the recent results of determination of the foF2 trends agree with the results of the detailed analysis of the data of stations in two hemispheres published by the authors. Possible causes of appearance of the negative trends in the parameters of the F2 layer at the cooling and contraction of the thermosphere due to anthropogenic effects. Currently, a decrease in the atoms-to-molecules ratio in the thermospheric gas and an increase in the rate of the ion-molecular reactions at the temperature decrease in the winter conditions are the most probable causes of appearance of the negative trends in foF2 in the winter months. A comparison of the trends in various parameters is performed and it is shown that these trends agree with each other.
Geomagnetizm i aeronomiya. 2025;65(3):343-350
343-350
MODEL OF THE POSITION OF THE MAIN IONOSPHERIC TROUGHT IN THE ECCENTRIC DIPOLE COORDINATES
Resumo
Based on the data of probe measurements of the electron density in the ionosphere on the CHAMP satellite from July 2000 to December 2007, an analysis of the possibility of using the coordinates of the eccentric dipole (ED) in the model for the invariant latitude of the minimum of the main ionospheric trough, Φm, was carried out. It has been established that the Φm model constructed from these data in the coordinates of the corrected geomagnetic (CGM) latitude can be used without changes in the ED coordinates, since the standard deviation of the model is less than the difference in the Φm values for these two options for specifying geomagnetic latitudes. The difference in the Φm values for these two options is minimal for the Southern Hemisphere and can be noticeable for the Northern Hemisphere, especially at the longitudes of the East Siberian Magnetic Anomaly. The dependence of Φm on local time and geomagnetic activity is the main one. The dependence of Φm on geographic longitude is relatively weak, therefore the difference in the Φm values between the CGM and ED coordinates even at the longitudes of the East Siberian Magnetic Anomaly is less than the standard deviation of the model.
Geomagnetizm i aeronomiya. 2025;65(3):351-357
351-357
RESPONSE OF THE IONOSPHERIC F2 LAYER TO THE GEOMAGNETIC STORM OF FEBRUARY 26‒28, 2023
Resumo
The results of studies of the behavior of the main characteristics of the F region of the ionosphere during a strong long-lasting magnetic storm on February 26–28, 2023 are presented. Variations in the critical frequency of the ionospheric F2 layer foF2 (characterizing the maximum electron density) and the height of the maximum of the F2 layer of ionosphere hmF2 are analyzed based on their relative deviations from quiet conditions. In the European region, a positive pre-storm anomaly in foF2 variations and a negative anomaly after the onset of a magnetic storm have been identified. It has been established that the hmF2 height changes greatly during a magnetic storm. The dependence of the ionospheric response on the location of the ionospheric station is shown.
Geomagnetizm i aeronomiya. 2025;65(3):358-369
358-369
NEW POSSIBILITIES OF OBLIQUE IONOSPHERIC SENSING USING PHASED ARRAY ANTENNAS
Resumo
Additional possibilities of the method of oblique ionospheric sounding with the measurement of the angle of location and azimuth of the radial trajectories of short-wave radio signals using receiving and transmitting phased array annular arrays with a software-controlled directional pattern are discussed. For a mid-latitude radio path for four days, experimental measurements at the receiving point of the radio path of the angles of arrival of modes of single-jump propagation of radio waves were compared with the results of calculations of radial trajectories for this radio path, performed using the empirical GDMI ionosphere model developed in IZMIRAN. It is shown that in the morning hours from 06:00 UT to 07:30 UT there is a good correspondence between the measured and calculated arrival angles, and in the daytime, to achieve the same correspondence, a slight correction of the distributions of ionospheric plasma parameters calculated using the GDMI model is required.
Geomagnetizm i aeronomiya. 2025;65(3):370-383
370-383
MANIFESTATION OF MESOSPHERIC BORES IN THE NIGHT AIRGLOW OVER YAKUTIA
Resumo
The article describes two cases of observation of mesospheric bores, which are prominent wave fronts observed using night airglow data recorded by all-sky cameras over the central part of Yakutia (northeastern Siberia). The purpose of the work is to study the peculiarities of propagation and formation mechanism of this phenomenon. In the first case, the manifestation of a bore in the emissions of hydroxyl OH molecules at the level of the mesopause (altitude 87 km) and the green line of atomic oxygen [OI] (altitude 97 km) is described. In the second case, a description of a bore recorded in the emission of hydroxyl OH molecules is presented. The wavelength, phase velocity of propagation, wave period, direction of propagation, time and duration of the phenomenon, are calculated. Possible sources of formation of the mesospheric bore are also discussed.
Geomagnetizm i aeronomiya. 2025;65(3):384-395
384-395
DEPTH TO THE BOTTOM OF LITHOSPHERIC MAGNETIC SOURCES IN MONGOLIA
Resumo
We estimate the depth to the bottom of lithospheric magnetic sources for the territory of Mongolia based on the global lithospheric magnetic field EMAG2v3 model using a centroid method. The obtained results are compared with independent geophysical data and a distribution of epicenters of regional earthquakes with M ≥ 5.0 for the observation period of 1900–2023. It has been found that the shallowest depths to the bottom of the lithospheric magnetoactive layer (<30 km) are seen predominantly under the mountain regions in Western and Central Mongolia and adjacent areas while the deepest bottom depths (>35 km) are observed to the east of 105° E. Therefore, the lithospheric magnetoactive layer is within the crust under the considered territory. A negative correlation between the Moho depth and the depth to the bottom of lithospheric magnetic sources is traced and there is a positive correlation between the lithospheric thickness and the depth to the bottom of lithospheric magnetic sources. We also demonstrate in this study that sources of the most earthquakes with M ≥ 6.0, recorded in 1900–2023, are nucleated in the areas in which a sharp change (>5 km) in the magnetoactive layer thickness is observed.
Geomagnetizm i aeronomiya. 2025;65(3):396-408
396-408
PALEOMAGNETIC DATING AND STRATIFICATION OF THE LATE PLEISTOCENE KARADZHA SECTION – THE REFERENCE SECTION OF THE NEOPLEISTOCENE PARATETHYS
Resumo
Late Pleistocene deposits of the Karadzha section have been studied. Both vector and scalar characteristics of the rocks composing it were obtained. The main paleomagnetic elements of the section have been established: the Jaramillo paleomagnetic horizon and the boundary of the Matuyama and Brunhes zones. In addition, a number of anomalous horizons (excursions) have been identified - these are Roxolans (Monot, Lachamp, etc.), Blake, Biwa I, Jamaica and Biwa III. This abundance of dated levels, along with track dates and abundant fauna, allowed a confident comparison of the studied section with the oxygen isotope scale for the last 0.8 million years.
Geomagnetizm i aeronomiya. 2025;65(3):409-416
409-416