O. V. Kapustina

DETECTION ON THE INTERCOSMOS-24 SATELLITE OF VLF AND ELF WAVES STIMULATED IN THE TOPSIDE IONOSPHERE BY THE HEATING FACILITY 'SURA'

Abstract Results are presented of a satellite experiment on the detection of VLF and ELF waves excited by irradiation of the night ionosphere F region by the field of a nonmodulated powerful radio wave. The excited VLF and ELF waves have been detected at topside ionosphere altitudes h = 500–1000 km in the frequency bands 7.5 kHz

Thunderstorm activity dynamics during hurricanes

Results of studying the thunderstorm activity dynamics during the Pacific hurricanes in August and October 2001, using broadband recording of the time forms of atmospherics on Kamchatka, have been presented. The number of atmospherics per minute at simultaneously determined azimuths of their sources has been used as an example of thunderstorm activity. An analysis of data processing results has indicated (a) in the absence of hurricanes, the maximal atmospheric flux level (10 ± 4 pulse/min) was observed at night, and the daylight level was 3 ± 1 pulse/min; (b) thunderstorm activity increases at the stage of tropical depression regardless of depression development into hurricane; in this case the flux of atmospherics can increase to 250 pulse/min at night and can be widely variable (5–100 pulse/min) in daytime; (c) in the sate of hurricane maturity, the thunderstorm activity level is not higher than the background level. It has been indicated that IGWs in the Earth’s atmosphere and the lower ionosphere are caused by lightning strokes accompanied by shock waves during expansion of the lighning channel. The results obtained are of interest in studying anomalous effects in the natural electromagnetic field in the VLF band during increased seismic activity on Kamchatka.

Variations of ULF-VLF electric fields in the external ionosphere over powerful typhoons in Pacific Ocean

Abstract The results of the preliminary studies of spatial and spectral characteristics of the ULF-VLF electric field absolute values in the topside ionosphere over the Pacific Ocean aquatory at h = 1500–2500 km in the daytime and at h = 550–700 km in the nighttime in September 1990 are presented. The registration results of the E component of the field by the narrow-band filters at frequencies of 8, 20, 33, 50, 75, 150, 225, 433, 623, 970 Hz, 9.6 and 15 kHz installed on board the Intercosmos 24 satellite were used. The spectral distribution of the E component of the field both in the day and night time qualitatively agrees with the propagation theory of the ULF-VLF wave whistler mode through the ionosphere, but the anomalously high field values in the daytime contradict this theory and the experimental data available. This may be related to giant lightning discharges over typhoons and amplification of the signal by focusing of ray trajectories at the daytime and defocusing them at the nighttime near equatorial anomaly.

Electric and Electromagnetic Processes in the Near-Earth Atmosphere before Earthquakes on Kamchatka

Simultaneous records of the diurnal variations in the quasistatic electric field in the near-Earth atmosphere, fluxes of discrete electromagnetic pulses in the VLF band, source azimuths, narrowband filter output emission intensity at frequencies of 4.65 and 5.3 kHz, and time forms and spectra of VLF pulses have been analyzed. The anomalous behavior of these parameters in October 2002 and August 2004 with different time delay was accompanied by earthquakes near the southeastern coast of Kamchatka at distances of 250–400 km from the registration points. Based on the results of a fine frequency-time analysis of the broadband records of VLF signals, it has been indicated for the first time that discrete electromagnetic pulses observed in anomalous fluxes before earthquakes were signals of local thunderstorm processes.

Power spectra of thermal tidal and planetary waves in the near-Earth atmosphere and in the ionospheric D region at Kamchatka

Spectral analysis of the diurnal variations in the quasi-static electric field in the near-Earth atmosphere and VLF atmospheric radio noise at a frequency of 5.3 kHz, simultaneously observed in September–October 1999 at Paratunka observatory of the Institute of Cosmophysical Research and Radiowave Propagation, has been performed. The variations in the intensities of the spectral power density and the period durations of the variations in the T ∼ 8–24 h band and higher as functions of geomagnetic and seismic activities have been studied.

Appearance of VLF and ELF-noises in topside ionosphere under the action of high power radio wave from data of satellite intercosmos-24☆

Results of a satellite experiment are presented on detection of VLF and ELF-waves excited by irradiation of the night ionosphere F-region by the field of a nonmodulated high-power radio wave. The excited VLF and ELF-waves have been detected at the topside ionosphere heights h=500–1000 km in the frequency bands 8 kHz<f<1.5 kHz and 10 Hz<f<1.5 kHz at distances less than 50–100 km from the centre of the magnetic force tube passing through the heated spot in the ionosphere. The region of wave appearance has well-defined boundaries. This points to propagation (guiding) of the observed low frequency waves along geomagnetic field lines. Possible mechanisms of observed low frequency emission generation are discussed. It is shown that longitudinal ELF-waves may be excited at the heights of topside ionosphere by beams of suprathermal electrons resulting from the action of high-power radio wave on the ionosphere. These waves have a small group velocity in the direction orthogonal to the magnetic field. Whistler waves in the VLF-band may result from conversion of lower-hybrid oscillations excited by the high-power wave into the whistler mode due to scattering by artificial small-scale field-aligned irregularities. The whistlers generated can propagate to the satellite along artificial ducts formed within the disturbed magnetic force tube.

Variations in the quasi-static electric field in the near-Earth’s atmosphere during geomagnetic storms in November 2004

The effects of the geomagnetic storms of November 8 and 10, 2004, in variations in the strength and power spectra of the electric field in the near-Earth’s atmosphere in Kamchatka were studied, together with the meteorological and geophysical phenomena observed simultaneously. A sequence of strong solar flares was shown to cause an anomalous increase in air temperature and humidity. This resulted in the excitation of anomalously strong thunderstorm processes in the atmosphere during the storm of November 8 and made it impossible to distinguish the effects associated with cosmic rays on this background. During the storm of November 10, on the background of weak variations in meteorological parameters, an increase in the strength and intensity of power spectra of the electric field on the day before the storm of November 10 was detected; it was followed by an attenuation of these parameters on the date of the storm. These effects were supposed to be associated with the action of cosmic rays on currents of the global electric circuit. It was shown that the influence of the Forbush effect of galactic cosmic rays in the power spectrum of the electric field first of all shows as the amplification of the component with the period T ∼ 48 h; in variations in humidity, the effect shows as the amplification of the component with T ∼ 24 h. Cause-and-effect relationships between variations in the electric field strength and the horizontal component of the geomagnetic field were shown to be absent both under the conditions of “fair weather” and during the storm of November 10. A diurnal negative-difference atmospheric pressure was detected on the second day after the geomagnetic storms of November 8 and 10.

Variations in electric and meteorological parameters in the near-Earth’s atmosphere at Kamchatka during the solar events in October 2003

The diurnal variations in the electric conductivity, electric-field strength, and meteorological parameters in the near-Earth’s atmosphere during the solar events in October 21–31, 2003, have been studied. It has been indicated that the conductivity and electric-field strength strongly depend on the air temperature and humidity. It has been found that the conductivity increased for 2 days before the geomagnetic storm on October 29–30 as a result of the effect of solar cosmic rays and decreased during a Forbush decrease in galactic cosmic rays, which was accompanied by a corresponding increase in the electric-field strength. It has been found that the air temperature and humidity anomalously increased in the process of solar activity, which resulted in the formation of different clouds, including thunderclouds accompanied by thunderstorm processes and showers. Simultaneous disturbances of the regular meteorological processes, solar flare series, and emission intensification in the near ultraviolet band, and visible and infrared spectral regions make it possible to consider these processes as a source of additional energy inflow into the lower atmosphere.

Problem of the nature of the sunrise effect in diurnal variations in the electric field in Kamchatka: 1. Time variations in the electric field

The effect of sunrise in time variations in the electric field in the near-Earth atmosphere at the Kamchatka Paratunka observatory has been studied. Twenty-nine records under fair-weather conditions have been selected. It has been indicated that the estimated effect parameters—the times of the effect’s onset and field strength maximum relative to the sunrise time, as well as the ratio of the strength maximum to its value before sunrise and the effect duration—coincide with the previously published data. Thereby, the conclusion is confirmed that the sunrise effect in diurnal variations in the electric field in the near-Earth atmosphere is related to the turbulence and convection processes in the atmospheric boundary layer at a change in atmospheric temperature.

Spectra of atmospheric waves in the dynamo region of the ionosphere at Kamchatka

A spectral analysis of the diurnal variations in the geomagnetic field horizontal component, observed at Kamchatka and Barrow polar observatory in September–October 1999, has been performed. The complete set of oscillations of thermal tidal atmospheric waves with T = 24, 12, 8, and 4 h has been detected in the variation spectral power (Sq) at Kamchatka, and only the fundamental harmonic with T = 24 h has been distinguished at Barrow. The above periods vary in both directions relative to stable maximums during strong geomagnetic disturbances. The relative spectral intensity at subharmonics also vary toward the fundamental harmonic with a period of 24 h. In the frequency band 0.5–3 h (IGW periods), the maximal intensity in the background spectra is observed at T ∼ 2 h and increases by an order of magnitude with increasing geomagnetic activity at both Kamchatka and Barrow. A day before earthquakes, the intensity of this maximum is below the rms background values, and the spectra widen toward the region of periods shorter than 2 h. A similar effect was previously observed in the power spectra of the diurnal variations in the quasistatic electric field and VLF noise, simultaneously measured in September–October 1999.