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The results of integrated instrumental observations of thunderstorm activity around Yakutsk at a radius of 400 and 30 km are presented. The seasonal course of thunderstorm activity was found to contain characteristic peaks in the first 10 days of June and the last 10 days of July or early August. The fraction of cloud-to-ground discharges in Central Yakutia is 40-60%, which is consistent with observations in Western Siberia (40-50%). The number of positive discharges to the ground was 8-15% of all cases of discharges to the ground, which is consistent with observations in Germany (17%) and slightly exceeds the observed number in the Caucasus (2.2-8.2%) and United States (4.5%). The thunderstorm activity in Yakutsk is three times higher than in the area around Yakutsk with a radius of 400 km, which can be explained by the fact that the city is a heat island. [ABSTRACT FROM AUTHOR]

Characteristics of thunderstorm cores, obtained from observations in Central and South Yakutia with the help of three one-point thunderstorm detectors with a radius of action of 300 km, located at Yakutsk, Mirnyi, and Neryungri, are presented. As a result of processing performed using two-step cluster analysis, the main parameters of thunderstorm cores have been obtained: number of discharges, area, intensity, transverse and longitudinal dimensions, shape, and lifetime. The distribution over occurrences of areas of cells has an exponentially falling form. It is shown that with increase of the mean area of an individual core S in a thunderstorm, the area occupied by this thunderstorm S grows exponentially, but with increase of the area of cores the density of discharges in them falls, and this dependence can be written in exponential form. The percent distribution of thunderstorms over density of discharges can be described by a falling power-law function. [ABSTRACT FROM AUTHOR]

The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results of azimuthal scanning, cross-sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter. The ratio of the amplitudes of electric and magnetic signal components, in the variations of which seismic effects before earthquakes can also be observed, has been considered. An analysis of the ratio makes it possible to increase the probability of predicting earthquakes when using the characteristics of the electromagnetic signals of lightning discharges as an additional method of complex monitoring of disturbances in the lower ionosphere caused by seismic processes. [ABSTRACT FROM AUTHOR]

We propose a technique for tool measurement of the lightning-discharge density in Yakutia in 2003–2006 by the radiophysical method using one- and two-point lightning detectors. The observed features of the spatio-temporal distribution and the parameters of thunderstorm cores are discussed. [ABSTRACT FROM AUTHOR]

Modulation of the VLF emission and riometric absorption byPc5 geomagnetic pulsations is studied in the period of strong geomagnetic disturbances on October 30-31, 2003. Some conclusions about the regime of pitch-angular diffusion into the loss cone are made. The better coincidence of VLF emission modulation with geomagnetic pulsations in other longitude sectors is explained by the global character of excitation of the pulsations and by damping of their amplitudes at the meridian of observation of the VLF emission, which is associated with intensification of auroral electrojets. [ABSTRACT FROM AUTHOR]

The features of the excitation of spatially localized long-period (10-15 min) irregular pulsations with a maximum amplitude of ~200 nT at a geomagnetic latitude of 66° in the morning sector 5 MLT are considered. Fluctuations were recorded against the background of substorm disturbances (maximum AE ~ 1278 nT). Antiphase variations of plasma density and magnetic field accompanied by vortex disturbances of the magnetic field both in the magnetosphere and the ionosphere have been recorded in the magnetosphere in this sector. Compression fluctuations corresponding to a slow magnetosonic wave have been recorded in the interplanetary medium in the analyzed period. It is assumed that pulsations have been excited in the localization of the cloud of injected particles in the plasma sheet by compression fluctuations caused by variations of the dynamic pressure of solar wind. [ABSTRACT FROM AUTHOR]

The space-time characteristics of geomagnetic pulsations during a sudden impulse on August 4, 2010 have been analyzed using ground-based and satellite observations. It has been indicated that two types of geomagnetic pulsations with different spatial extensions, oscillation frequencies, and generations were observed at that time. It has been found that geomagnetic pulsations with identical oscillation frequencies (∼4.5 mHz) at different latitudes were observed, with a maximal amplitude in the dusk sector. Oscillations with close frequencies were registered in the solar wind in the IMF B component. Higher-frequency (7-10 mHz) pulsations dependent on latitude were registered on the dawn side. It is assumed that geomagnetic pulsations with frequencies of ∼4.5 mHz were caused by oscillations penetrating from the interplanetary medium, and higher-frequency pulsations were Alfvén resonance oscillations generated during the compression of the magnetosphere. An asymmetric oscillation amplitude distribution relative to noon was caused by the IMF orthospiral orientation in this event. [ABSTRACT FROM AUTHOR]

Effects of the solar eclipse on March 29, 2006 on signals of VLF radio stations, regular radio-noise intensity in the VLF range 0.3–10 kHz, and the number of atmospherics registered in Yakutsk mainly from the western direction are considered. The full lunar shadow zone consistently shaded the daytime section of the radio-signal propagation path from the western coast of Africa to Altai. A multichannel parallel analyzer-recorder (operating in the frequency range 0.47–8.7 kHz), one-point thunderstorm direction-and-range finder (0.3–100 kHz), narrow-sector radio-noise direction finder (0.3–10 kHz), recorder of VLF radio-station signals, and broadband radio-noise recorder (0.3–100 kHz) were used for observations. Time synchronization of the recorder of VLF radio-station signals was carried out with the help of GPS-clocks. The effect was observed in radio-station signals, radio-noise, and number of atmospherics from a direction of (270 ± 20)°, counted from the north clockwise, in the last stage of the eclipse (∼11–12 UT), when the lunar shadow approached the night terminator and crossed the signal propagation path. The effect was manifested through a ∼20% gain of the received signals, ∼40% increase in the number of atmospherics, and radio-station phase changes. The registered effects are similar to those we observed during the eclipse on March 9, 1997. [ABSTRACT FROM AUTHOR]

We study the response of the ionosphere and magnetosphere to a sudden commencement (SC) on October 29, 2003, at 06:11 UT. It is shown that the geomagnetic response had the form of two successive stages. In the first ~5 min after the SC, a strong intensification of a two-vortex current system of the DP2 type was observed in latitudes ~67°-65°, with variations of ?H-4000 nT (+700 nT). At the same time, energetic electrons were injected without dispersion to geosynchronous orbits simultaneously in the sectors ~16, ~04, and ~07 MLT. In the subsequent 5-15 min, a new intensification of the western electrojet took place in all time sectors at latitudes ~70°. Around midnight, this electrojet was extended in the poleward direction up to the polar cap latitudes (F’ ˜ 75°-83°). It had an unusually high velocity of extension (up to ~5.0 km/s) and was accompanied by typical dispersionless substorm injections, but only at meridians ~04 and 07 MLT. From comparing the development of electrojets with the data of satellite observations in the solar wind and magnetosphere, we suggest that ~3-5 min after the SC onset a dipolization of the magnetic field at the geosynchronous orbit occurred. It was connected with the decay of the current flowing across the magnetotail. The subsequent extension of the region of current decay into the tail up to 150RE proceeded with a velocity of =1000 km/s, which exceeds the known velocities of such an extension by a factor of ~5. [ABSTRACT FROM AUTHOR]

The averaged data of observations oflightning strikes in North Asia in 2009-2014 are presented. The pattern is retrieved from the data of World Wide Lightning Location Network (WWLLN); one station of this network is located in Yakutsk. The dependence of thunderstorm activity on latitude, longitude, and altitude is demonstrated. [ABSTRACT FROM AUTHOR]

Considered are the methods of thunderstorm cells clustering using the data of one-point and multipoint lightning detectors and their characteristic features based on the observations in Yakutia. As the thunderstorm activity intensifies, i.e., the lightning discharge density in the region increases, the number of storm centers and the number of cells in the center grow up. The sizes and the lifetime of thunderstorm cells in Yakutia correspond to the similar data for North America and the European part of Russia. The maximum area and intensity of both center and thunderstorm cell are observed at the stage of development, in the middle of their lifetime. As the cell area increases, the intensity of lightning discharges decreases inversely to the area. It is revealed that as the cell oblongness increases, the intensity of lightning discharges in these cells becomes higher as well. [ABSTRACT FROM AUTHOR]

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009-2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1-3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10 cm s. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m. [ABSTRACT FROM AUTHOR]

The results of measurements of levels of electric and magnetic radiation fields from lightning discharges are presented. Lightning discharges occurred in the region of the terrestrial surface bounded by a sector of ∼90° with a radius of ∼30–300 km. A power spatial dependence of the electromagnetic radiation field components of lightning discharges is established. The results of measurements are interpreted using fractal geometry methods. [ABSTRACT FROM AUTHOR]