Time variations in the amplitude and phase of signals of the Russian telecommunication station (the frequency is 25 kHz) on the Arkhangelsk—Kharkov path with a length of about 1600 km on the day of the August 1, 2008 solar eclipse (SE) and on the adjacent days are analyzed. Two types of effects are detected. An increase of the signal amplitude by approximately 32% in comparison with the background days and the 2.1 μs time shift of the signal during 2—2.5 h is referred to the first type. Changes in the spectral composition of the quasiperiodic disturbances in the ionosphere presented the second type of the effects. For spectral analysis of the quasiperiodic variations in the amplitude and phase of the radio signal, the window Fourier transform, adaptive Fourier transform, and wavelet transformation were applied simultaneously. In the period of SE and after it, oscillations with periods of 10—15 min (according to the amplitude data) and also about 10 and 18 min (according to the phase data) were intensified. Based on radio signal characteristics, the parameters of ionospheric disturbances are estimated.

Variations in the amplitude and phase of VLF radiowaves in the ionosphere during the August 1, 2008, solar eclipse

We have analyzed the observational results for variations in the main geomagnetic field and its fluctuations in the range of periods 1–1000 s that accompanied the approach of the Chelyabinsk space body to the magnetosphere and ionosphere of the Earth. The measurements were conducted with a magnetometerfluxmeter near the city of Kharkiv, as well as with the network of magnetometers located at the observatories of Novosibirsk, Kyiv, Lviv, Almaty, Khabarovsk, Arti, Borok, and Yakutsk. Variations in the main geomagnetic field and its fluctuations approximately 33–47 min prior to the explosion of the Chelyabinsk meteoroid have been discovered; they persisted for 25–35 min and were probably associated with meteoroid passage through the magnetosphere. The amplitude of variations reached 1–6 nT. We have proposed a model of the generation of aperiodic, quasi-periodic, and noise-like variations in the geomagnetic field induced by the approach of a space body.

Magnetospheric Effects during the Approach of the Chelyabinsk Meteoroid

Numerical model of the Chelyabinsk meteoroid as a strengthless object

The need for speed in Near-Earth Asteroid characterization

Abstract We have used Minor Planet Center (MPC) data and tools to explore the discovery circumstances and properties of the currently known population of over 10,000 NEAs, and to quantify the challenges for follow-up from ground-based optical telescopes. The increasing rate of discovery has grown to ∼1000/year as surveys have become more sensitive, by 1 mag every ∼7.5 years. However, discoveries of large ( H ≤ 22 ) NEAs have remained stable at ∼365/year over the past decade, at which rate the 2005 Congressional mandate to find 90% of 140 m NEAs will not be met before 2030 (at least a decade late). Meanwhile, characterization is falling farther behind: Fewer than 10% of NEAs are well characterized in terms of size, rotation periods, and spectral composition, and at the current rates of follow-up it will take about a century to determine them even for the known population. Over 60% of NEAs have an orbital uncertainty parameter, U ≥ 4 , making reacquisition more than a year following discovery difficult; for H > 22 this fraction is over 90%. We argue that rapid follow-up will be essential to characterize newly discovered NEAs. Most new NEAs are found within 0.5 mag of their peak brightness and fade quickly, typically by 0.5/3.5/5 mag after 1/4/6 weeks. About 80% have synodic periods of 3 years that would bring them close to Earth several times per decade. However follow-up observations on subsequent apparitions will be difficult or impossible for the bulk of new discoveries, as these will be smaller ( H > 22 ) NEAs that tend to return 100× fainter. We show that for characterization to keep pace with discovery would require: quick (within days) visible spectroscopy with a dedicated ≥ 2 m telescope; long-arc (months) astrometry, to be used also for phase curves, with a ≥ 4 m telescope; and fast-cadence ( min ) light curves obtained rapidly (within days) with a ≥ 4 m telescope. For the already-known large ( H ≤ 22 ) NEAs that tend to return to similar brightness, subsequent-apparition spectroscopy, astrometry, and photometry could be done with 1–2 m telescopes.

The need for speed in near-Earth asteroid characterization

Various observational data including infrasound, seismic, optical (onboard) monitoring, ground video and photo records, and evidence from witnesses of the Chelyabinsk event on February 15, 2013, have been analyzed. The extensive material gathered has provided a base for investigations of the physical properties of the object, the results of which are discussed. A bolide light curve is constructed, which shows a multiplicity of flashes. Estimations of the energy of the meteoroid explosion, which took place in the atmosphere at an altitude of about 23 km, show evidence of the formation of a high-power shock wave equivalent to 300–500 kilotons of TNT. The object diameter corresponding to this energy falls within the range 16–19 m. The trajectory of the meteor is outlined. It is preliminarily concluded that the Chelyabinsk meteorite was a representative the Apollo asteroid family.

Astronomical and physical aspects of the Chelyabinsk event (February 15, 2013)

A description of the Center of Geophysical Monitoring for Systematic Investigation of Negative Consequences for the Human Environment and Infrastructure of the City of Moscow Resulting from Natural and Technogenic Factors, which is part of the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IGD RAS), is presented. The results of synchronous observations of the seismic vibrations, electric and acoustic fields, and atmospheric meteoparameters performed at the Center and in the Mikhnevo Geophysical observatory of IGD RAS situated outside of the zone of the Moscow influence are examined. It is shown that the megalopolis influence consists of an increase in the amplitudes of the physical fields, a change in their spectral composition, and the violation of natural periodicities. A technogenic component that has a considerable impact on the natural physical processes in the surface atmosphere is an important factor that characterizes a megalopolis.

Geophysical fields of a megalopolis

Geophysical effects of the March 29, 2006, solar eclipse

Based on complex analysis of the results of instrumental observations during strong atmospheric disturbances, it is shown that hurricanes and squalls are accompanied not only by high wind velocities, but also by high-amplitude microbaric variations, variations in amplitudes of the microseismic background, and the vertical component of the electric field It is established that 1–4 hours before the onset, squalls and hurricanes are characterized by increased amplitudes of microbaric variations in the range of periods of 2–6 min, as well as by low-frequency variations in the electric field and variations in the microseismic background, which together with the meteorological parameters can be considered as a complex prognostic criterion of an impending hurricane (squall)

Variations in Geophysical Fields during Hurricanes and Squalls

—A new phenomenological model describing the propagation of acoustic disturbances in the stratospheric waveguide is proposed based on instrumental observations of infrasound signals from high-power explosive sources in the atmosphere. A generalized relationship between the energy of the acoustic source in the atmosphere and the characteristic frequency in the spectrum of the acoustic signal is obtained. The developed model is verified against the description of natural and manmade acoustic sources with the known energy. It is shown that the proposed model agrees with the observations and the data obtained in the other works.

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Yu. S. Rybnov

Papers

Astronomical and physical aspects of the Chelyabinsk event (February 15, 2013)

Geophysical fields of a megalopolis

Geophysical effects of the March 29, 2006, solar eclipse

Variations in Geophysical Fields during Hurricanes and Squalls

Relationship between the Parameters of Infrasound Waves and the Energy of the Source