The frequency of occurrence of a certain level of the rate of change of geomagnetic activity can be expressed as a power law with an exponent of the order -1.7, and the probability of exceedance of a given level can be expressed by the law lg(P) = -0.0517 (dB / dt) – 0.1946. The largest high-frequency variations are noted during the recovery phase of magnetic bay and correspond to geomagnetic pulsations of the Pc5 range (a period of variations of 200-300 s). On a pipeline on these pulsations other high-frequency variations are imposed and they start earlier – from a maximum of bay of disturbance. It is noted the need of monitoring and forecasting of magnetic storms and recommendations on the allocation of periods, during which one cannot disable protection for preventive works.
Observation of low-frequency radio signals may be used as a tool of remote monitoring of seismic disturbances in the lower ionosphere. In the case of using a low frequency radio signal the most informative parameter is a signal phase. When using natural low-frequency radio emissions - electromagnetic signals of lightning discharges (atmospherics), the variation of the signal amplitude is analyzed. For strong (magnitude greater than 5) and not deep-focus (focal depth is less than 50 km) earthquakes it is found that the effects of earthquakes and their precursors in the signals of atmospherics appeared in the form of increasing amplitude, whose duration is generally a few hours. In this work peculiar properties of the effects of manifestations in the signals of atmospherics of deeper earthquakes are considered on the example of the events in the Malaysian-Indonesian region.
KEYWORDS: Solar processes, Interference (communication), Signal attenuation, Radio propagation, Global Positioning System, Antennas, Atmospheric sciences, Electromagnetism, Navigation systems, Receivers
Diurnal variations of radio noise intensity (14.88 kHz) registered in Yakutsk in June 2009-2014 is 10 dB, March - 9 dB, September - 8.7 dB, December - 7.3 dB. Diurnal variations of intensity of radio station VLF signals, radio noise intensity and the number of lightning discharges in Yakutsk are compared. VLF noise variations in summer 5-10 UT defined local thunderstorm activity. The period 11-20 UT for receiving radio noise defined distant thunderstorm cells in Western Siberia, the territory between Hinggan, Buretsky and Stanovoy mountaines. Radio signals from these areas propagate in similar paths like signals Novosibirsk and Khabarovsk navaid stations. The attenuation variations from a solar activity minimum to the maximum are estimated. Taking into account the changes of propagation attenuation of 1.2 dB (signal Khabarovsk) from a minimum to a maximum of solar activity in July, the power of VLF radio noise at a minimum on 7.6 dB greater than at solar activity maximum.
Features of the remote sensing of seismic disturbances in the lower ionosphere are considered according to observation data of lightning electromagnetic signals passing over the earthquake epicenter, in Yakutsk. The technique has the ability to scan a large seismically active region or even several regions directly from one point, though in some azimuths there are limitations due to insufficiently high lightning activity. In last case, the receiving of signals at several spaced points is used.
The estimate on spatial distribution of lightning flash density over North Asia (40-80 N, 60-180 E) is presented from results of instrumental observations by the World wide lightning location network (WWLLN) during 2009-2014. There are two massive thunderstorm centers. The lightning density dependence on longitude and latitude caused by west air transfer and storm activity northward decrease is revealed. The region of Yakutia is considered individually.
There were found 94 trains of radiosignals of lightning flashes from 4 thunderstorms in 2010-2012 years of observation over Yakutia. As it was considered in literature, 91% lightning flashes were negative. There were only 8 flashes with positive discharges. Lightning was found to be able to contain about 11 return strokes; the average is 3-4 strokes per flash. The time interval between subsequent strokes generally varies within 130 ms with the mean of 50 ms. One interval was found to be over 300 ms.
KEYWORDS: X-rays, Solar radiation models, Radio propagation, Data modeling, Solar processes, Satellites, Wave propagation, Waveguides, Transmitters, Receivers
Phase variations and sudden phase anomalies (SPA) VLF signals registered in Yakutsk from Novosibirsk radio station (14.9 kHz) for summer and winter daytime propagation conditions are considered. The threshold SPA sensitivity by Xrays flux P depends on the season weakly. SPA magnitude at fixed solar zenith angle X and X-ray flux P from summer to winter on the Novosibirsk – Yakutsk path is increased, SPA dependence on averaged along the propagation path of the cosine solar zenith angle is sharper in summer. X-ray flux is estimated according to the phase variations of the Novosibirsk radio signals. A satisfactory agreement with the simulated flux data from the satellite has been obtained booth in SPA, and unperturbed daytime conditions.
For distant monitoring of disturbances in the lower ionosphere signals of low-frequency radio stations are often used. In particular, the method is used for investigation of ionospheric responses (disturbances) caused by seismic activity. As a variant of this method for the detection of seismic disturbances in the ionosphere one can use natural radio signals - an electromagnetic radiation of thunderstorm discharges (atmospherics). The examples of the effects of three earthquakes in the variations of average amplitude of atmospherics received in Yakutsk (φ = 62.1° N, λ = 129.7° E) were considered. The increase of signal amplitude for some days before the events can be considered as a precursor. It allows to used observations of impulse electromagnetic thunderstorm signals as one of possible means of distant monitoring of strong earthquakes.
Effects of a solar eclipse 29.03.06 in signals of VLF radio stations, in intensity of the regular radio noises in the
frequency band 0,3-10 kHz, and in quantity atmospherics, accepted in Yakutsk preferentially from the western direction
surveyed. The area of the complete lunar shadow consistently shaded a day time part of a line of distribution of radio
signals from the western Africa edge up to Altai.
Observations were conducted with the help of the multichannel analogue parallel analyzer - registrar (in a frequency
band 0,47-8,7 kHz), one point a thunderstorm direct-distance finder (0,3-100 kHz), narrow-sector finding of VLF-noise
radiation sources (0,3-10 kHz), the registrar of signals of the VLF radio stations and the broadband registrar of radio
noises (0,3-100 kHz). Time sync of the registrar of signals of the VLF radio stations was carried out with the help of
GPS-clocks.
The effect was observed in signals of radio stations, radio noises and quantity atmospherics from a direction 270º ± 20º,
digitized from the north clockwise, at last stage of an eclipse (~11-12 UT) when the lunar shadow approached to a line
night terminator and intercrossed a line of distribution of signals. The effect was showed as amplification of signals on
~ 20 % and magnifications of quantity atmospherics on ~ 40 %. The registered effects are similar observed by us earlier
for an eclipse 09.03.97.
Thunderstorm activity variations relative to the onset of > 10 MeV proton flow rise and in the periods of galactic cosmic ray decreases (Forbush-effects) are studied by the superposed epoch technique. Thunderstorm activity is estimated by VLF-noise level registered in Yakutsk. In summer day and winter night hours the decrease of the VLF- noise level up to minimum is observed on the third day after the proton burst and then the increase - on the forth-fifth day. With respect to the onset of Forbush-decreases one can distinguish two phases of the effect: during the first phase the decrease of the VLF-noise amplitude occurs on the 0, -1 day, and during the second one the increase takes place on the +1, 2 day with the excess of the initial undisturbed level. The obtained results allow to connect the considered reasons and to imagine the thunderstorm activity variations in common sequence. The simultaneous consideration of effects shows that the decrease of the VLF- noise level is caused by the burst of protons and the increase of the noise level during subsequent days is caused by GCR Forbush-decreases.
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