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Vol 57, No 1 (2017)

Article

Magneto-ionospheric effects of the solar eclipse of March 20, 2015, over Kharkov

Chernogor L.F., Garmash K.P.

Abstract

The results of observations of disturbances in the lower and middle ionosphere and in the geomagnetic field accompanying the partial solar eclipse over Kharkov are presented. The ionospheric effects have been studied with the use of an ionosonde and measurements of the phase and amplitude of a radio signal with a frequency of 66.(6) kHz on the Moscow–Kharkov route, and the effects in the magnetic field have been analyzed with the help of a magnetometer–fluxmeter in the range of periods from 1 to 1000 s. Disturbances in both the lower and middle ionosphere, as well as in the geomagnetic field, have been detected. The observation results have been compared with the results of a simulation of physical processes accompanying the solar eclipse. A good agreement has been found between observational and modeling results.

Geomagnetism and Aeronomy. 2017;57(1):72-83
pages 72-83 views

Telluric currents have no significant effect on the Earth’s core seismicity

Chernogor L.F.

Abstract

We show that telluric currents have no effect on the formation of macrofaults in the Earth’s crust or on implementation of the intensification regime. This is mainly associated with the weakness of telluric currents and induction of the geomagnetic field.

Geomagnetism and Aeronomy. 2017;57(1):119-120
pages 119-120 views

Types of spectra of ion flux fluctuations in the solar wind and magnetosheath at the interface between inertial and dissipative ranges

Riazantseva M.O., Rakhmanova L.S., Zastenker G.N., Ermolaev Y.I.

Abstract

This paper considers the features of turbulent characteristics of ion flux variations in the solar wind and magnetosheath at the scale of 0.01–10 Hz based on measurements on the BMSW plasma spectrometer (Plasma-F experiment) mounted on the Spektr-R satellite. A variability of types of fluctuation frequency spectra is shown. Fluctuation spectra with certain features in the transition region from the inertial to the dissipative range are selected (a sharp knee in the fluctuation spectrum, plateau and peak in the knee, and a nonlinear spectrum bend at high frequencies). The degree of difference between the observed spectra and the spectra characteristic of the developed isotropic turbulence in the Kolmogorov model is determined. The probability of observation of the spectra of certain types is estimated. The features of fluctuation spectra in the solar wind and magnetosheath are compared for each type of spectra.

Geomagnetism and Aeronomy. 2017;57(1):1-7
pages 1-7 views

Prediction of relativistic electron flux in the Earth’s outer radiation belt at geostationary orbit by adaptive methods

Myagkova I.N., Dolenko S.A., Efitorov A.O., Shirokii V.R., Sentemova N.S.

Abstract

The paper investigates the possibilities of the prediction of the time series of the flux of relativistic electrons in the Earth’s outer radiation belt by parameters of the solar wind and the interplanetary magnetic field measured at the libration point and by the values of the geomagnetic indices. Different adaptive methods are used (namely, artificial neural networks, group method of data handling, and projection to latent structures). The comparison of quality indicators of predictions with a horizon of 1–12 h between each other and with the trivial model prediction has shown that the best result is obtained for the average value of the responses of three neural networks that have been trained with different sets of initial weights. The prediction result of the group method of data handling is close to the result of neural networks, and the projection to latent structures is much worse. It is shown that an increase in the prediction horizon from 1 to 12 h reduces its quality but not dramatically, which makes it possible to use these methods for medium-term prediction.

Geomagnetism and Aeronomy. 2017;57(1):8-15
pages 8-15 views

Generation of auroral kilometric radiation in inhomogeneous magnetospheric plasma

Burinskaya T.M., Shevelev M.M.

Abstract

The generation of auroral kilometric radiation in a narrow 3D plasma cavity, in which a weakly relativistic electron flow is propagated along the magnetic field against a low-density cold background plasma, is studied. The time dynamics of the propagation and intensification of waves are analyzed using geometric optics equations. The waves have different wave vector components and start from the cavity center at an altitude of about the Earth’s radius at plasma parameters typical for the auroral zone at this altitude. It is shown that the global inhomogeneity of the Earth’s magnetic field is of key importance in shaping the auroral kilometric radiation spectra.

Geomagnetism and Aeronomy. 2017;57(1):16-23
pages 16-23 views

Proton interaction with quasi-electrostatic whistler mode waves in an inhomogeneous plasma (magnetosphere)

Shklyar D.R., Titova E.E.

Abstract

We study the interaction between energetic protons of the Earth’s radiation belts and quasi-electrostatic whistler mode waves. The nature of these waves is well known: whistler waves, which are excited in the magnetosphere due to cyclotron instability, enter the resonant regime of propagation and become quasielectrostatic, while their amplitude significantly increases. Far enough from the equator where proton gyrofrequency and transversal velocity increase the nonlinear interaction between these waves and energetic protons becomes possible. We show that plasma inhomogeneity may destroy cyclotron resonance between wave and proton on the time scale of the order of particle gyroperiod which in fact means the absence of cyclotron resonance; nevertheless, the interaction between waves and energetic particles remains nonlinear. In this case, particle dynamics in the phase space has the character of diffusion; however, the diffusion coefficients are determined by the averaged amplitude of the wave field, but not by its resonant harmonics. For real parameters of the waves and magnetospheric plasma, proton pitch-angle diffusion leading to their precipitation from the magnetosphere becomes essential.

Geomagnetism and Aeronomy. 2017;57(1):24-31
pages 24-31 views

A new type of daytime high-frequency VLF emissions at auroral latitudes (“bird emissions”)

Manninen J., Turunen T., Kleimenova N.G., Gromova L.I., Kozlovskii A.E.

Abstract

This paper is concerned with a new, previously unknown type of high-frequency (above 4 kHz) VLF emissions that were detected during winter VLF campaigns in Kannuslehto (L ~ 5.5), Finland. These previously unknown emissions have been discovered as a result of the application of special digital filtering: it clears the VLF records from pulse signals of intensive atmospherics, which prevent other kinds of VLF emissions in the same frequency range from being seen on spectrograms. As it appears, aside from wellknown bursts of auroral hisses and discrete quasiperiodic emissions, a previously unknown type of daytime right-hand polarized VLF waves is also present at frequencies above 4 kHz. These emissions can persist for several hours as series of separate short discrete wideband (from 4 to 10 kHz and higher) signals, each with a duration between one and several minutes. It has been found that such signals can be observed almost daily in winter. These emissions sound like bird’s chirping to a human ear; for that reason, they were called “bird emissions.” The dynamic spectra of individual signals often resemble flying birds. The signals are observed during daytime, more often in magnetically quiet conditions preceded by geomagnetic disturbances. As a rule, the occurrence of these bird emissions is accompanied by a slight increase in electron density in the lower ionosphere, which is evidence of the precipitation of energetic (>30 keV) electrons. This raises a number of questions as to where and how the VLF bird emissions are generated and how such emissions, at frequencies greatly exceeding half the electron equatorial gyrofrequency at L ~ 5.5, can reach the Earth’s surface.

Geomagnetism and Aeronomy. 2017;57(1):32-39
pages 32-39 views

Amplitude–frequency characteristics of ion–cyclotron and whistler-mode waves from Van Allen Probes data

Lyubchich A.A., Demekhov A.G., Titova E.E., Yahnin A.G.

Abstract

Using two-hour (from 2300 UT January 25, 2013 to 0100 UT January 26, 2013) measurement data from Van Allen Probes on fluxes of energetic particles, cold plasma density, and magnetic field magnitude, we have calculated the local growth rate of electromagnetic ion–cyclotron and whistler-mode waves for field-aligned propagation. The results of these calculations have been compared with wave spectra observed by the same Van Allen Probe spacecraft. The time intervals when the calculated wave increments are sufficiently large, and the frequency ranges corresponding to the enhancement peak agree with the frequency–time characteristics of observed electromagnetic waves. We have analyzed the influence of variations in the density and ionic composition of cold plasma, fluxes of energetic particles, and their pitch-angle distribution on the wave generation. The ducted propagation of waves plays an important role in their generation during the given event. The chorus VLF emissions observed in this event cannot be explained by kinetic cyclotron instability, and their generation requires much sharper changes (“steps”) for velocity distributions than those measured by energetic particle detectors on Van Allen Probes satellites.

Geomagnetism and Aeronomy. 2017;57(1):40-50
pages 40-50 views

Reaction of the high-latitude lower ionosphere to solar proton events from observations in the ELF range

Lebed’ O.M., Larchenko A.V., Pil’gaev S.V., Fedorenko Y.V.

Abstract

The reaction of the lower ionosphere to the solar proton events that occurred in 2011–2012 is studied in this paper based on the results of measurements of the propagation velocity and the Ez/Hτ ratio of the low-frequency electromagnetic pulses (atmospherics) in the ELF range at the high-latitude observatories Lovozero and Barentsburg. With numerical modeling methods, it is shown that horizontal local irregularities of the lower ionosphere conductivity profile could be a cause of the splashes in the Ez/Hτ ratio observed in the experiment during the solar proton event of March 7, 2012, which was a unique event in both the proton flux value and energy.

Geomagnetism and Aeronomy. 2017;57(1):51-57
pages 51-57 views

Earth’s lower ionosphere during partial solar eclipses according to observations near Nizhny Novgorod

Bakhmetieva N.V., Vyakhirev V.D., Kalinina E.E., Komrakov G.P.

Abstract

The results of observations in the Vasil’sursk Laboratory (56.1° N, 46.1° E) of partial solar eclipses of August 11, 1999, August 1, 2008, and March 20, 2015 are discussed. Ionospheric observations in the eclipse periods and on control days were conducted by the method of resonant scatter of radio waves at artificial periodic irregularities of the ionospheric plasma and the partial reflection method based on radio wave scatter by natural irregularities in the D region. The lower ionosphere reaction to solar eclipses, including variations in the electron concentration and characteristics of the signals scattered by APIs, was studied. An intensification of the lower ionosphere turbulization, an increase in the signal amplitudes backscattered by APIs in the E region, stratification of the D region, and the arrival of scattered signals from mesopause heights were observed during the eclipses. A decrease in the electron concentration of the D region up to a factor of 3–5 was found by the partial reflection method. Above 88 km, the ionospheric response was delayed by 20–25 min relative to the moment of the eclipse maximum phase, whereas this delay in the lower part of the D region was 2–4 min.

Geomagnetism and Aeronomy. 2017;57(1):58-71
pages 58-71 views

Modification of electron concentration in the ionosphere in the pump-wave plasma resonance region

Istomin Y.N., Kim V.Y.

Abstract

We discuss the propagation of sounding radio waves in the inhomogeneous ionosphere, in the reflection area of which there are small-scale artificial magnetically-positioned irregularities. The propagation of radio waves in such an area, where the lateral dimensions of strongly elongated artificial irregularities are smaller than the wavelength, has a diffraction nature. It is shown that the calculation of diffraction parameters makes it possible to derive the amplitude of density irregularities and their relative area perpendicular to the magnetic field direction. Comparison of theoretical calculations with experimental studies on modification of the electron density altitude profile by heating of the ionosphere with midlatitude stand Sura showed that the relative area of the negative density perturbations can reach several percent.

Geomagnetism and Aeronomy. 2017;57(1):84-92
pages 84-92 views

Dynamics of large-scale ionospheric inhomogeneities caused by a powerful radio emission of the Sura facility from the data collected onto ground-based GNSS network

Kogogin D.A., Nasyrov I.A., Grach S.M., Shindin A.V., Zagretdinov R.V.

Abstract

The measurements of variations in the total electron content of the Earth’s ionosphere along the GPS satellite signal propagation path are described. The signal parameters were measured at a network of receivers at three distant sites: Sura (Vasilsursk), Zelenodolsk, and Kazan. They are arranged along the geomagnetic latitude of the Sura Facility under short-wave radio irradiation of the ionosphere. One feature of the experiment is the crossing of a disturbed region by the radio path between a GPS satellite and Vasilsursk. This resulted from the angular sizes of the Sura array pattern; the radio paths between a GPS satellite and Zelenodolsk and a GPS satellite and Kazan did not cross. Variations in the total electron content of up to 0.15−0.3 TECU were revealed at all three sites during four experimental campaigns (March 2010, March 2013, May 2013, and November 2013). The lateral scale of an ionospheric disturbance stimulated by a high-power radio wave and the velocity of its west-to-east propagation along the geomagnetic latitude were 30–60 km and 270–350 m/s, respectively. A decrease in the total electron content (down to 0.55 TECU) was recorded along the Kazan–Zelenodolsk–Vasilsurks line, which is connected with the solar terminator transit; the lateral scale of the related ionospheric inhomogeneities was ~65–80 km.

Geomagnetism and Aeronomy. 2017;57(1):93-106
pages 93-106 views

Nonzonal structure of the response of the global field of the Earth’s atmospheric temperature to solar activity

Krivolutsky A.A., Dement’eva A.V.

Abstract

The work describes the results of calculations obtained with the Atmospheric Research Model (ARM) general circulation model. The temperature response of the troposphere and middle atmosphere to variations in UV solar radiation were found to have a large-scale wave structure when planetary waves at the lower model boundary were taken into account. In the present paper, the results from the processing of global temperature fields with three databases (ERA-20C, NOAA-CIRES 20th Century Reanalysis, v2, and NCEP/NCAR Reanalysis I) are provided. Analysis of the differences of the mean monthly temperature global fields (January and July) between the maxima and minima of three solar activity cycles (21, 22, and 23 cycles) also demonstrated their nonzonal structure. It was shown that the amplitude of this difference in January in the stratosphere (10 hPa) can be 7–29 K in the Northern Hemisphere. In July, this effect is prominent in Southern Hemisphere. In the troposphere (500 hPa), a nonzonal temperature effect is present in both the Northern and Southern Hemispheres; the amplitude of the effects amounts to approximately 5–12 K. In conclusion, we discuss that the mechanism of solar energy impact on atmospheric temperature discovered by numerical modeling is supported after reanalysis data processing.

Geomagnetism and Aeronomy. 2017;57(1):107-112
pages 107-112 views

Higher helicity invariants and solar dynamo

Sokolov D.D., Illarionov E.A., Akhmet’ev P.M.

Abstract

Modern models of nonlinear dynamo saturation in celestial bodies (specifically, on the Sun) are largely based on the consideration of the balance of magnetic helicity. This physical variable has also a topological meaning: it is associated with the linking coefficient of magnetic tubes. In addition to magnetic helicity, magnetohydrodynamics has a number of topological integrals of motion (the so-called higher helicity moments). We have compared these invariants with magnetic helicity properties and concluded that they can hardly serve as nonlinear constraints on dynamo action.

Geomagnetism and Aeronomy. 2017;57(1):113-118
pages 113-118 views