Geomagnetizm i aeronomiya

The unresolved problems of the physics of auroral substorms include the issue of localization and the mechanism of the start of the substorm expansion phase. The new information needed to solve this problem can be obtained by comparing the results of observations from low-altitude spacecraft with observations in the equatorial plane of the magnetosphere. For this purpose, the morphological projection method was used, which does not require knowledge about the configuration of the magnetic field. This paper considers the latitudinal profiles of the auroral precipitation characteristics at ionospheric altitudes obtained from DMSP F7 spacecraft observations and the radial distribution of ion pressure in the equatorial plane according to the THEMIS mission during periods of magnetic calm and at time intervals close to the auroral breakup. Special attention was paid to the position of the maximum energy flux of the precipitation of ions with energy larger than 3 keV and ion pressure profiles. The average ion pressure latitudinal profiles at low altitudes were determined and compared with the average pressure distributions in the equatorial plane of the magnetosphere under similar to averaged values of solar wind and geomagnetic activity parameters. It is shown that, if under geomagnetic calm the pressure maximum at low altitudes is mapped to geocentric distances of ~7−8 Re, before the substorm onset it is mapped to a distance of ~5−6 Re. The averaged values of the pressure maxima during the magnetic calm, as well as before and after substorm onset were obtained. The brightness of the auroral luminosity in the 557.7 nm emission was estimated from DMSP F7 observations of the average energy and energy flux of the precipitated electrons.

To diagnose and forecast the state of the heliosphere, as well as space weather and climate, it is necessary to know the temporal changes of galactic cosmic rays flux at the Earth’s orbit. The aim of the work is to forecast the cosmic ray flux for the next century based on the relationship between the modulation of galactic cosmic rays and the characteristics of solar activity. For a long-term forecast, one parameter models of solar activity were used that determines the modulation of galactic cosmic rays – the number of sunspots or the potential of cosmic rays solar modulation. As a result, a long-term forecast of the cosmic ray flux was obtained based on the analysis of a dozen models of solar activity behavior for the next century. The analysis suggests that, contrary to earlier forecasts, the probability of a large solar minimum at the end of the 21st century is small. This is shown by the majority of long-term solar activity forecasts by various authors which was analyzed by us. An almost twofold increase in the level of solar activity is expected by the middle of the century and a subsequent transition to approximately current level at the end of the century. Reduced intensity of galactic cosmic rays is expected at the Earth’s orbit by mid-century.

To study electromagnetic signals and search for functional connections with sources of disturbances of natural and anthropogenic origin, digital equivalents of recording observations in the frequency range from 20 Hz to 20 kHz on satellites over the Caribbean are used. Graphs of the dependence of the number of signals per minute on time along the satellite orbit are plotted. Fractionally dispersed whistlers at frequencies below 1 kHz (ELF fdw) ranged from 30 to 100% of the total number of fdw. This estimate coincides with the results of ground-based observations of the ELF atmospherics (“tails”) under different conditions. There was an increased frequency of occurrence of fdw and ELF fdw during the action of typhoons in the Pacific Ocean, especially at the stage of depression, and hurricanes in the Atlantic, in the area located on both sides of the meridian passing through the Brazilian anomaly. These results are confirmed by the work of other researchers.

A new analytical representation of the electric potential is obtained for the classical non-stationary model of the global electrical circuit of the atmosphere, occupying a spherical layer, the conductivity of which increases exponentially along the radius. The boundary conditions of the model take into account the relationship between the values of the electric potential and current at magnetically conjugate points of the upper boundary of the atmosphere. Using the obtained representation, the potential distribution for a current dipole in a spherical layer is analyzed. New asymptotic formulas for the electric potential of a current dipole at t→∞ at each point of the spherical layer are obtained. An analytical expression for the Green’s function of the corresponding initial-boundary value problem is found.

Determination of the boundaries of anomaly-forming bodies (deep sources) is an important step in interpreting potential field anomalies during geophysical research. In this paper, a method based on continuous wavelet analysis of magnetic profiles is proposed to solve this problem. The connection between the parameters of simple bodies and the properties of the wavelet transformation of the field created by these bodies is shown. A technique has been developed for determining the boundaries of blocks of the magnetically active layer. The proposed method was tested on model data of the simplest single bodies and on a spreading model. The high resolution of the method is shown, which makes it possible to determine the boundaries of blocks of the spreading model with an accuracy of up to 400 m. The method was applied to a real magnetic profile crossing a typical oceanic structure: the mid-ocean Reykjanes Ridge. The results obtained confirm that the proposed method has a higher resolution compared to the analytical signal and allows the identification of narrow blocks. To clarify the boundaries of these blocks, it is planned to develop a methodology based on the modeling results.

We performed a Fourier and wavelet analysis of solar activity in the range between the period of the Hoyle magnetic cycle (~22 years) and the Gleisberg cycle (50-120 years) in 1000-1900. Two reconstructions of the number of sunspots from indirect data were used based on: a) the number of low-latitude auroras and b) the concentration of 14C in tree rings. Our analysis showed that in the spectra of both reconstructions, there is a pronounced stable variation with a period of ~30-40 years, which is present even during grand minimums/maxima. The source of this variation is the frequency modulation by the Suess cycle with a period of ~200 years, resulting in a three-frequency structure with carrier oscillation with a period of ~35 years and sideband periods of ~30 and ~40 years. Some difference in the obtained spectra of the two reconstructions may be due to the different contribution of closed and open magnetic fields in the restoration of solar activity from different indirect data.