Abstract Experiments involving the radio sounding of solar plasma with signals from the Venus Express and Mars Express spacecraft, which were carried out from October 6 to December 6, 2006, provided data on frequency fluctuations of the radio signals for the western and eastern coronal limbs. The processing of this data provided information on the intensity of the frequency fluctuations, a parameter

Abstract The properties of the annual asymmetry in the electron density of the F2-layer maximum NmF2 at noon are analyzed based on the global empirical model of the F2-layer critical frequency median (SDMF2 model). As a characteristic of this asymmetry, we used the R index, i.e., the January/July ratio of the total (at a given and geomagnetically conjugate points) NmF2 density at noon averaged over

Abstract In the Parker model of the heliospheric magnetic field, the ratio of the azimuthal field component \({{B}_{{{\varphi }}}}\) to the radial component \({{B}_{r}}\) depends only on the radial speed V of the solar wind and coordinates of the observation point (\(r,\,\theta \)): \({{{{B}_{{{\varphi }}}}} \mathord{\left/ {\vphantom {{{{B}_{{{\varphi }}}}} {{{B}_{r}}}}} \right. \kern-0em} {{{B}_{r}}}}

Abstract The F2-layer critical frequency foF2 is analyzed for three days preceding a magnetic storm based on Juliusruh station data. A total of 272 storms over the period 1976–2010 are considered, and 2682 events (foF2 deviations from quiet conditions) are found. There were 2007 deviations with positive signs and 675 deviations with negative signs. It was found that the aforementioned deviations demonstrate

Abstract In this paper, we have analyzed how the change in the solar activity is able to affect the IRI-2016 outcomes for different latitudes. We have compared the IRI-2016 model predictions with F2 layer critical frequency (foF2) data derived from the low (Manila), middle (Rome and Kiev) and high (Sodankyla) latitude ionosonde stations during high (1980) and low (1986) solar activity periods. In order

Abstract In this paper, we have analyzed TEC data obtained at Indian stations such as Agra, Lucknow, Hyderabad, Bangalore, and Port Blair and VLF amplitude data of NWC fixed frequency (f = 19.8 KHz) transmitter signals recorded at Agra for ±15 days from the day of occurrence of a strong earthquake of magnitude M = 8.5 on 11 April, 2012 in Indonesian region. The analysis is performed using well established

Abstract The results of a study of the dependence of the dynamics of relativistic electron fluxes of the Earth’s outer radiation belt on the geomagnetic storm intensity are presented. A total of 22 geomagnetic storms with |Dst|max of ∼50 to ∼200 nT are considered. The studies are based on experimental data on fluxes of electrons with an energy of ~2 MeV received from the Van Allen Probe spacecraft

Abstract The correlation between the rate of TEC index (ROTI) and amplitude scintillation index S4 for low-latitude region is analyzed using data collected from a Global Positioning System (GPS) scintillation monitoring receiver installed at Bahir Dar Ethiopia for the periods of 2012 and 2013. The analysis was done for selected quiet and disturbed days based on Kp and Dst values. Generally speaking

Abstract We examined cycles of solar activity reconstructed based on the number of auroras observed at the middle and low latitudes in 1000–1700. We used a wavelet analysis method. Variations in the Earth’s magnetic moment influence the propagation of cosmic particles that cause auroras. We took this influence into account when reconstructing solar activity based on variations in the number of auroras

Abstract In September 2019, two out-of-service power transmission lines were used as a horizontal emitting antenna in an experiment conducted on the Kola Peninsula to generate ultra-low-frequency (ULF, 0.38–6.4 Hz) and extremely low–frequency (ELF, 9.4–194 Hz) signals during nighttime hours. The current ranged from 240 A at low frequencies (LF, 0.382 Hz) to 20 A at the highest frequencies (194 Hz)

Abstract The results of numerical modeling of the influence of the main factors distorting the paleomagnetic record in sedimentary rocks are presented: signal averaging and inclination underestimation and estimation of the parameters of secular variations (their amplitude, the degree of elongation of the distribution of directions, and the direction of elongation of this distribution) recorded in sedimentary

Abstract The Latitudinal dependence in the response of the Ionospheric F2-layer electron density (NmF2) and peak height (hmF2) to three geomagnetic storms of May and August 2010 has been examined. The data-sets used for the study were obtained from Ilorin, Nigeria (1.87° S/76.67° E), San Vito, Italy (34.68° N/90.38° E), Hermanus, South Africa (42.34° S/82.15° E), and Pruhonice, Czech Republic (45.66°

Abstract The paper presents the results of numerical modeling of the propagation in the high latitude region of ultra-long radio waves at the carrier frequencies of the long-range navigation radio engineering system (RSDN-20). Computational experiments were carried out for different distributions of the ionospheric electron concentration, which were constructed based on data from the EISCAT 42m incoherent

Abstract A large array of experimental data from observations of ionospheric stations located in different regions of the world is used to consider the variations in the height of the F2-layer maximum during ionospheric disturbances of solar and magnetospheric origin. The proposed algorithm for the calculation of hmF2 describes the height behavior at any point on the Earth with respect to the current

Abstract The results of a numerical simulation of the dynamics of the airglow of the atomic oxygen red line (630 nm) due to ionospheric heating by high-power, high-frequency (HF) radio emission are presented. The simulation was based on a system that incorporates an equation for the electron temperature Te (thermal conductivity) with a localized heating source near the reflection point of the pump

Abstract In this paper, we consider the processes associated with the formation of a so-called foreshock region ahead of the front of a near-Earth collisionless shock wave. In the proposed theoretical model, ions in the ramp or the front of the shock wave are shown to be accelerated to significant energies. The physical conditions under which these ions accelerated in the shock front end up in front

Abstract With monthly average temperature series in the contiguous United States during the period from January 1895 to July 2018, the author uses wavelet analysis to investigate possible connection between the average temperature and solar activity. The results show obvious fluctuation characteristics in the temperature series. The modulation action from solar activity plays an important role in the

Abstract This paper presents a statistical analysis of global ionospheric variation during quiet and disturbed geomagnetic conditions from December 2008 to June 2019. The study comprehends ascending and descending solar periods of the 24th solar cycle. The vertical Total Electron Content (vTEC) data of CODE-GIM are utilized to reveal the TEC variation in the regional and global regions. The disturbance

Abstract The summer mesopause region (altitudes of 82–92 km) is the coldest place in the Earth’s atmosphere; it is influenced by external effects, including lunar tides. In this study, we isolate the lunar tidal harmonics from the temperature series of the hydroxyl emission layer (OH*) obtained from spectrophotometric measurements at the Zvenigorod scientific station of the Obukhov Institute of Atmospheric

Abstract The results of the forecasting of quasi-stationary and transient solar wind streams velocity for a period from May to December 2010 are presented. The velocity of quasi-stationary solar wind streams on the near-Earth orbit was calculated with the empiric model based on an analysis of solar images obtained in the extreme ultraviolet. The velocity and arrival time of the interplanetary coronal

Abstract Data from a long-term experiment with monitoring of the vertical component of the electric field at the base from the surface to the bottom showed oscillations with quasi-periods of tens to hundreds of days in Lake Baikal. They are not caused by any internal sources, but they show a close relationship with intermittent oscillations of the solar X-ray radiation flux. This relationship is characterized

Abstract A large array of experimental data from observations of ionospheric vertical sounding stations located in different regions of the Earth has been used to study the features of long-term (1948–2019) time series of relative variations in the critical frequencies of the ionospheric F2 layer during disturbances. The ionospheric disturbance parameters, such as the amplitudes of positive disturbances

Abstract The stability and dynamics of the interaction of soliton-like solutions of the generalized nonlinear Schrödinger (NLS) equation describing the dynamics of the envelope of modulated nonlinear waves and pulses (including the phenomenon of wave collapse and the self-focusing of wave beams) in plasma (including space one), as well as in nonlinear optical systems, have been studied with allowance

Abstract The results of a statistical study of the polarization characteristics of irregular geomagnetic Pi3 pulsations observed in polar regions of the magnetosphere and the effect of interplanetary conditions on them are presented. One-minute digital observations of the magnetic field of the Heiss Island (HIS, Φ' = 74.80°, Λ' = 144.46°) and Mirny (MIR, Φ' = –76.93°, Λ' = 122.92°) observatories are

Abstract The concept of “instantaneous” polarization of the horizontal electric component of the Pc1 pulsation field as measured by the coastal and base (offset from the coast) telluric lines is used to separate the contributions of geomagnetic pulsations and extraneous noise, the excitation of which is a possible change in the concentration of sea aerosols in the surface layer of the atmosphere and

Abstract— This work is a continuation of the author’s earlier analysis of the relationship between the most often used solar-activity index, F10.7, and solar-activity indices (Ly-α, Rz and Mg II) that reflect variations of the ultraviolet radiation of the Sun, which governs the behavior of the main ionospheric layers. It is shown that the relationship between F10.7 and the three aforementioned indices

Abstract The response of strong magnetic storms in variations of the electric field of the near-ground atmosphere of the midlatitudes are studied according to data from long-term observations of aeroelectric (Ez) and geomagnetic fields at the midlatitude Borok Geophysical Observatory. For the period 1998–2015, 19 strong and very strong magnetic storms with a minimal Dst index of < –100 nT and a maximal

Abstract The correlations between variations in the geomagnetic cutoff rigidity of cosmic rays and the Dst and Kp geomagnetic indices and solar-wind and IMF parameters are calculated for the three phases of the magnetic storm of November 20–21, 2003: before the storm and during its main and recovery phases. The correlations are the strongest between variations in the cutoff rigidity and the Dst index

Abstract The dependence of the local annual asymmetry index AI on solar activity has been analyzed based on daily data on the noon values of the F2-layer maximum electron density, NmF2, at the Boulder and Hobart ionospheric stations for 1963–2002. The AI index characterizes the relative difference in the total electron density NmF2 in January and July for a given pair of stations. The weighted-average

Abstract The total solar eclipse on July 2, 2019, has been studied by using data of the La Serena ground magnetic station in Chile located in the path of the totality (at geographic coordinates: 29.827° S, 71.261° W). The event reached 100% darkness and occurred from 1522:34 hr to 1746:36 hr LT. We monitored the X, Y, Z‑components of the geomagnetic field with a fluxgate magnetometer to investigate

Abstract Modern geodynamo models allow the generation of a magnetic field without reversals and with frequent reversals. The transition from one regime to another is associated with a relatively small change in the intensity of the generation sources. From this, it is usually concluded that the geodynamo system is located near such a transition, which, generally speaking, requires a more detailed justification

Abstract A method is proposed to determine the total height profiles of the electron density in the ionosphere with the use of topside satellite ionograms containing traces of sounding signal reflections from the Earth’s surface. The monotonic profile from the satellite to a certain height hm above the height hmF2 of the F2-layer maximum is calculated with the classical method based on reflections

Abstract The calculation results and experimental data on the formation and development of a polarization jet in subauroral latitudes are compared. It is shown that the alternation of vertical and horizontal components of the ionospheric plasma–drift velocity leads to different variations in the main parameters of the F2 layer. An increase in the critical frequency of the F2 layer is revealed in certain

Abstract The Mg II core-to-wing ratio (c/w ratio) data is used to derive the solar extreme UV emission which brings a vital role in the creation of the Earth’s ionosphere region. A continuous Mg II c/w ratio data has scientific importance towards the analysis of the earth’s climate as well as for the solar chromosphere region. Various instruments of ESA and NASA satellites such as SUSIM, SOLSTICE,

Abstract The equatorial anomaly dynamics in the winter solstice is studied based on data from topside sounding of the ionosphere from the Interkosmos-19 satellite for high solar activity. This is the final study on the construction of the pattern of equatorial anomaly variations under conditions of high solar activity. Changes in the equatorial anomaly structure with local time and longitude are considered

Abstract Homogeneous series of solar cosmic-ray events for four solar-activity cycles against the background of decreased activity in cycles 23 and 24 are considered. The number of solar cosmic-ray events with energies above 10 MeV decreased insignificantly, while the number of ground-level enhancements in comparison between cycles 23 and 24 decreased by eight times. It is shown that the average contribution

Abstract Some authors suggest that space weather events may affect daily weather variables, such as air temperature and atmospheric pressure. Associations between space weather events and daily weather variables have been analyzed in four Baltic airports near Kaunas, Vilnius, Riga, and Tallinn during 2000–2016. We hypothesized that space weather events, 1–5 days before or after them, and intersection

Abstract A brief description of the multipath coherent radio technique installation is presented. Its goal is continuous monitoring of the dynamical processes in the ionosphere caused by space weather variations and the impact of high-energy sources in the Earth–atmosphere–ionosphere–magnetosphere system. The variations of radio-wave characteristics (the Doppler spectra and signal amplitudes) in the

Abstract On the basis of the results of theoretical studies of the manifestation of seismic activity it was shown that as a result of the impact on the atmosphere and the neutral component of the ionosphere of the acoustic pulse caused by a Rayleigh surface wave, both in ground-based experiments and in satellite observations at heights of the F-region of the ionosphere the perturbations of the vertical

Abstract A study of the wave changeability in the F2-layer critical frequency over Kaliningrad (54.6° N, 20° E) and Irkutsk (53° N, 103° E) stations during strong sudden stratospheric warmings is presented. Low solar activity was a common factor for all selected cases. The results of wavelet analysis of the time variations in foF2 showed that an amplification of the oscillations with periods of 4–10

Abstract The possible use of artificial neural networks—classical multilayer perceptrons—with coupling functions to forecast time series of the Dst geomagnetic index is studied. The basic forecast is based on parameters of the solar wind and interplanetary magnetic field measured at the libration point L1 in an experiment on the ACE spacecraft. It is shown that the largest contribution to the improvement

Abstract Numerical values of the criteria for the efficiency of the determination of the critical frequency of the F2 layer of ionosphere over European Russia are calculated with ionospheric models corrected based on vertical-incidence sounding data from an ionosonde. Two correction techniques are considered: the selection of an effective value of the input heliogeophysical index and linear-correlation

Abstract The paper presents the results of a study of the relationship of seismic events with geomagnetic disturbances arising from the acoustic impact on the lower ionosphere, which are caused by vibrations of the Earth’s surface at distances of several thousand kilometers from the earthquake source. The measurements were carried out at Mikhnevo Observatory, which is equipped with an instrumental

Abstract A significant proportion of publications related to the ionospheric disturbances that arise during earthquake preparation over the regions of their preparation refer to these disturbances as anomalies. In this case, the identification of the ionospheric precursor is actually based on an estimate of the amplitude of the deviation of the ionospheric parameters from the undisturbed value. We

Abstract The system for the preparation of quasi-definitivedata of the INTERMAGNET standard is described. Unlike the final data, which was prepared no earlier than 1 year after the measurement, the data provided with the described system are available 1 day after the last series of absolute observations. Quasi-definitivedata are used to model fast variations in the main magnetic field of the Earth

Abstract Under the assumption that the evolution of the total electron content (TEC) in a quiet ionosphere can be described within the framework of the linear dynamic-stochastic approach, the corresponding model is constructed and verified. The TEC data archive for 1998–2018 of the Crustal Dynamics Data Information System (CDDIS) of the National Aeronautics and Space (NASA) Administration was used

Abstract A new analytical model for the generation of axially symmetric jets (directed jets) in a nondissipative, nonequilibrium stratified plasma has been created in the magnetohydrodynamics approximation. The model is based on the assumption of Schwarzschild convective instability in plasma and on the condition that the magnetic field lines are frozen into matter. It is shown that jets with poloidal

Abstract Oscillations of coronal loops with electric currents from one base to another are studied. The energy of longitudinal currents can be a source of energy for loop flares (Alfvén and Carlqvist, 1967). A simplified model of a loop in the form of a composite cylindrical magnetic tube containing a shell with a potential azimuthal magnetic field is considered for the theoretical study of oscillations

Abstract The heliospheric modulation potential was reconstructed based on data from the North Greenland Ice Core Project (NGRIP) on the content of the cosmogenic isotope 10Be in the Greenland ice from the end of the 14th century CE. This time interval includes global solar-activity minima, such as the Spörer (≈1460–1550 CE), Maunder (≈1645–1715 CE), and Dalton (≈1790–1830 CE) minima. The reconstruction

Abstract The results of long-term mesoscale observations in the microwave range are reviewed. The rationale for the resumption of observations at the Havana Radio Astronomy Station is justified. Domestic observations at a wavelength of λ5 cm have a long observation interval and can effectively complement the global series of observations. A comparative analysis of the results of solar observation in

Abstract The directivity of transverse electromagnetic waves generated in a plasma at a double plasma frequency during the coalescence of plasma waves is calculated for various angular distributions of these waves. It is shown that the directivity of the generated electromagnetic waves is determined by the angular distribution of the spectral energy density of the Langmuir waves and is practically

Abstract The possibility that large-scale coronal loops of solar-type stars and M dwarfs make a significant contribution to the white-light continuum emission is considered. It is shown that that the existence of high-density (>1012 cm–3) coronal loops contradicts the standard model of solar and stellar flares. As a result, the optical flare emission cannot be determined by free–free or free–bound

Abstract The rotational effect observed in variations of areas of polar coronal holes with a period of 14 days is analyzed with SDO data by using Coronal Hole Identification with the Multithermal Emission Recognition Algorithm (CHIMERA) algorithm and the algorithm for the identification of solar structures from neural networks. A physical interpretation of the observed rotational effect associated

Abstract Solar-climatic correlations were examined over the timescales, corresponding to solar cycles of Schwabe, Hale and Gleissberg, during the last 3–4 centuries using eight proxy and direct indices of: (a) summer climate in Fennoscandia, (b) sea surface temperature in the North Atlantic and (c) solar activity. Using novel and improved data records new evidences of a link between solar activity

Abstract—The main subject of the study is an analysis of time series of the width of annual rings of spruce and pine (D) that were obtained during the implementation of a scientific project supported by the Institute of Astronomy of the Bulgarian Academy of Sciences and the Ministry of Agriculture and Food in 2012–2014. The project is a continuation of our previous study (Komitov and Kaftan, 2019)

Abstract Changes in the umbra brightness and in the magnetic field over time should occur on long-period sunspot oscillations in accordance with Birman’s idea of inhibition of circulation (overturning) convection by a strong vertical magnetic field in antiphase mode.When the sunspot as a whole shifts upward, its power flux tube expands with a fixed magnetic flux, the magnetic field decreases, and the

Abstract Calculated insolations of the Earth are analyzed. The main trends in the modern solar climate change are identified: increased latitudinal contrast and smoothed seasonal differences. The correlation of the meridional insolation gradient with the average annual energy transfer in the ocean–atmosphere system is revealed. The features of changes in the annual and semiannual meridional insolation

Abstract The paper presents a modified version of a previously published 3D model of the solar facular knot (Solov’ev and Kirichek, 2019), which successfully describes the main structural features of the solar facular formations. As in the main model, we use the solution (Schatzman, 1965) in the potential approximation as the basis of the magnetic structure of the facular element. The magnetic profile

Abstract The paper presents the results of processing of data on the soft X-ray solar radiation obtained by the PINGVIN-M instrument aboard the KORONAS-FOTON spacecraft in July 2009. The high sensitivity of the device, combined with effective compensation for the magnetospheric background over most of the orbit, made it possible to study in detail the evolution of X-ray radiation from the active region

Abstract Polar and low-latitude faculae were identified in daily images based on white-light observations from the MDI (1996–2011) and SOHO (2010–2019) space observatories. The boundaries of the faculae were combined with magnetic field observations at the closest possible instant of observation. The time and latitude distributions, as well as other properties of polar and low-latitude faculae, were