Ranges of AGW propagation in the Earth’s atmosphere

The propagation of atmospheric gravity waves (AGWs) is studied in the context of geometrical optics in the nonisothermal, viscous, and thermal-conductive atmosphere of Earth in the presence of wind shifts. Parametric diagrams are plotted, determining the regions of allowed frequencies and horizontal phase velocities of AGWs depending on the altitude. It is shown that a part of the spectrum of AGWs propagates in stationary air in an altitude range from the Earth’s surface through the ionospheric F1 layer. AGW from nearearth sources attenuate below 250 km, while waves generated at altitudes of about 300 km and higher do not reach the Earth’s surface because of the inner reflection from the thermosphere base. The pattern changes under strong thermospheric winds. AGW dissipation decreases with an adverse wind shift and, hence, a part of the wave spectrum penetrated from the lower atmosphere to the altitudes of F2 layer.     

Model of muon generation in the Earth’s atmosphere

The muon fluxes on the Earth’s surface and at depths of 7, 20, and 40 m of water equivalent are calculated based on a simple model of pion generation by primary particles with different energies. This generation model is based on the known concepts of multiple pion production. The model parameters are compared with the data obtained using accelerating machines.     

Afternoon Pc5 geomagnetic pulsations on the Earth’s surface and in the ionosphere (STARE radars)

Two cases when Pc5 geomagnetic pulsations were registered at the IMAGE Scandinavian network of stations and with STARE radars in the afternoon sector (1700–1800 MLT) during the recovery phase of the moderate magnetic storm are analyzed in detail. Using the ground-based observations, it has been indicated that classical quasimonochromatic resonance Pc5 pulsations were observed in the first case (on October 12, 1999; Kp = 5); in this case the maximal amplitude of the spectral maximum at a frequency of 2.5 mHz was registered at Φ ～ 65°. Two maximums were observed in the spectrum in the second case (on October 13, 1999; Kp = 4): ～2.5 mHz (the same maximum) and 2.9 mHz; in this case the maximal oscillation amplitude (2.5 mHz) shifted to Φ > 67°. These results were compared with the echo signal intensity simultaneously registered with the STARE Finland radar on a beam oriented along the 105° geomagnetic meridian. The spatial-temporal maps of the Pc5 pulsation amplitude latitudinal distribution (“keograms”), constructed based on the radar measurements in the wide range of geomagnetic latitudes (63°–70°) where the resolution was substantially higher than that of the ground-based observations, made it possible to detect two regions spaced in latitude (Φ ～ 65° and Φ ～ 67°–68°) with the simultaneous excitation of oscillations (double resonance?), between which the plasmapause projection was supposedly located.     

Influence of the atmospheric surface layer on the penetration of the electric field from the earth’s surface into the ionosphere

In the used model, the quasistationary electric field in the atmosphere of the Earth is obtained by solving the conductivity equation. The penetration characteristics of the electric field from the Earth’s surface into the ionosphere depend on both atmospheric and ionosphere conductivity. The ionosphere is taken into account by setting a special condition on the upper boundary of the atmosphere. The influence of the atmospheric surface layer with a reduced conductivity on the penetration of the electric field from the surface of the Earth into the ionosphere is analyzed.     

The effect of wind on the gravity wave propagation in the Earth’s ionosphere

The effect of ionospheric wind on the gravity wave propagation is studied. These waves arise in the ionosphere due to intensification of their sources near the Earth’s surface during enhanced seismic activity. The influence of the wind on these waves is connected with the Ampere’s force that produces the ion-drag force acting on the atmosphere. This results in the occurrence of the discrete wave spectrum the maximum of which increases in proportion to the numbers of the natural scale. Furthermore, these waves are amplified during propagation from the source region in the direction perpendicular to the wind direction. These peculiarities of the gravity waves can be used for monitoring of seismic activity based on the ionosphere sounding.     

Formation of large-scale disturbances in the upper atmosphere caused by acoustic gravity wave sources on the Earth’s surface

The results of a model study of the acoustic gravity wave (AGW) propagation from the Earth’s surface to the upper atmospheric altitudes have been considered. Numerical calculations have been performed using a nonhydrostatic model of the atmosphere, which takes into account nonlinear and dissipative processes originating when waves propagate upward. The model source of atmospheric disturbances has been specified in an area localized on the Earth’s surface. The disturbance source frequency spectrum includes harmonics at frequencies of 0.5ωg-1.5ωg (ωg is the Brunt-Väisälä frequency near the Earth’s surface). The calculations indicated that AGW propagation and dissipation over the source result in the fact that the region of large-scale spatial disturbances of the upper atmosphere mean state is formed at ～200 km altitudes. This region substantially affects AGW propagation and results in waveguide propagation of AGWs with periods shorter than the Väisälä-Brunt period at the altitude of a disturbed atmosphere. The dissipation of AGWs propagating in such a waveguide results in a waveguide horizontal expansion. The extension of the disturbed region of the mean state of the upper atmosphere and, consequently, the waveguide length can reach ～1000 km, if the AGW ground source operates for ～1 h. The physical mechanism by which large-scale disturbances are formed in the upper atmosphere, based on the propagation and dissipation of AGWs with periods shorter than the Väisälä-Brunt period in the upper atmosphere, explains why these disturbances are rapidly generated and localized above AGW sources located on the Earth’s surface or in the lower atmosphere.     

Reflectionless acoustic gravity waves in the Earth’s atmosphere

The vertical wave propagation in an inhomogeneous compressible atmosphere is studied in the framework of a linear theory. Under specific conditions imposed on atmospheric parameters, solutions can be found in the form of travelling waves with variable amplitudes and wave numbers that do not reflect in the atmosphere in spite of its strong inhomogeneity. Model representations for the sound speed have been found, for which waves can propagate in the atmosphere without reflection. A wave energy flux retains these reflectionless profiles, which confirms that energy can be transferred to high altitudes. The number of these model representations is fairly large, which makes it possible to approximate real vertical distributions of the sound speed in the Earth??s atmosphere using piecewise reflectionless profiles. The Earth??s standard atmosphere is shown to be well approximated by four reflectionless profiles with weak jumps in the sound speed gradient. It has been established that the Earth??s standard atmosphere is almost completely transparent for the considered vertical acoustic waves in a wide range of frequencies, which is confirmed by observational data and conclusions derived using numerical solutions of original equations.     

Lunar–solar tide effects in the Earth’s crust and atmosphere

The gravitational interaction in the Earth–Moon–Sun system is considered from the standpoint of influencing the formation of time variations in the geophysical fields and some natural processes. The analysis of the results of instrumental observations revealed the main periodicities and cycles in the time variations of subsoil radon volumetric activity with the same periods as the vertical component of the variations of the tidal force. The amplitude modulation of seismic noise by the lunar-solar tide is demonstrated. It is shown that the intensity of relaxation processes in the Earth’s crust has a near-diurnal periodicity, whereas the spectrum of groundwater level fluctuations includes clearly expressed tidal waves. Based on the data on the tilts of the Earth’s surface, the role of tidal deformation in the formation of the block motions in the Earth’s crust is analyzed. A new approach is suggested for identifying tidal waves in the atmosphere by analyzing micropulsations of the atmospheric pressure with the use of adaptive rejection filters.     

Effect of the magnetic field on measurements of the electron density and temperature by cylindrical probes in the Earth’s ionosphere

In the 1960s and 1970s, quite simply produced cylindrical Langmuir probes were used in the USSR both on satellites (Kosmos-378, Intercosmos-2, -4, -8, -10, -19) and to measure the electron density and temperature on vertical launched rockets (Vertical’-4, -6, -10) within the Intercosmos program. These measurements were first made at middle latitudes. With increasing inclination of the orbits of launched satellites (satellites had no stabilization), falling sections were sometimes observed on probe characteristics in the electron saturation region. The Intercosmos-Bulgaria-1300 satellite, which was stabilized along three axes and was equipped with a cylindrical probe whose longitudinal axis was always directed downward to the Earth, was launched in 1981. This satellite allowed definite conclusions on the effect of the geomagnetic field on the form of the probe characteristic and, hence, on the determination of the electron density and temperature. Probe characteristics with falling sections are presented. These measurements are compared with those performed in a laboratory plasma. The appearance of negative sections on the probe characteristics is shown to be due to the effect of the geomagnetic field. The degree of this effect depends both on the electron density and temperature and on the probe voltage.     

Influence of solar activity on variations in the density of the Earth’s upper atmosphere

This article studies long-period variations in the Earth’s upper atmosphere density over several solar activity cycles, using long-term data on the evolution of motion of three artificial satellites (Intercosmos-19, Meteor-1-2, and Cosmos-1154) in orbits at heights of 400–1000 km. The time interval when the satellites were in the orbits covered three solar activity cycles (partly the 21st, completely the 22nd, and partly the 23rd). It is found that the variations in the average density of the upper atmosphere at heights of 400–600 km in the 1980–2000 period were governed by the changes in the solar activity level.     

Penetration of the Earth’s free oscillations at 54 minute period into the atmosphere

It is known that the fundamental spheroidal mode ₀S₂ of the Earth free oscillation with a period of about 54 min forces atmospheric oscillations. We present a certain phase relationship for components of the ₀S₂ multiplet, which is based on synchronous collocated microbarograph and seismograph observations. This relationship is both the first observational manifestation of the Pekeris mode of global atmospheric oscillations with the 54 min period and a further proof of the Earths ₀S₂ mode penetrating into the atmosphere. We show that the linear non-dissipative model of steady forced oscillations in isothermal atmosphere at rest does not describe the penetration of the ₀S₂ mode into the atmosphere adequately.     

New approach to the construction of the Earth’s upper atmosphere model using the satellite local data on the atmosphere

The present-day models of the Earth’s upper atmosphere make it possible to construct the spatial-temporal pattern of variations in the atmospheric parameters on the planetary scale in essence in the averaged form. The set of data on the satellite deceleration in the atmosphere, probe measurements aboard geophysical rockets, and radiowave incoherent scatter measurements in the Earth’s atmosphere are used to construct these standard models. The current level of the space studies makes it possible to use a new method to study the Earth’s upper atmosphere: to study the upper atmosphere by measuring the absorption of the solar XUV radiation by the Earth’s atmosphere during the solar disk observations.     

Effects of lunar-solar tides in the variations of geophysical fields at the boundary between the Earth’s crust and the atmosphere

Extraterrestrial forcing of natural environmental processes by gravitational interaction between the Sun, the Moon, and the Earth is considered. Based on the instrumental data, the main periodical components and cycles are identified in the time variations of some geophysical fields at the boundary between the Earth’s crust and the atmosphere. Correlation analysis shows that the lunar-solar tides are the key factor responsible for diurnal and quasi-biweekly variations in the ground electric field, radon emanation, water level in wells, and microseismic vibrations. The tidal influence on the various-scale movements of the blocks of the Earth’s crust is analyzed. In the context of the vertical, lateral, and rotational motion of crustal blocks, which is very important for the platforms, a new, precession-like type of displacements is revealed. These movements develop as a result of the nonsynchronous tidal responses of the block and the adjacent interblock gaps or tectonic structures whose strength and strain properties are different in different directions.     

Estimation of the temperature in the Earth’s interior from surface measurements of the electromagnetic field

The possibility of contactless remote estimation of the temperature in the Earth’s interior from surface magnetotelluric (MT) measurements is examined. The neuronet analysis of MT and temperature measurements in the Bishkek geodynamic research area (the Northern Tien Shan) showed that a contactless electromagnetic geothermometer can in principle be realized. An optimal method including MT measurements and treatment of available thermograms is developed. The method minimizes uncertainties of the remote temperature estimation. The use of six to eight thermograms for calibration of electromagnetic data is shown to provide a 12% relative error of prediction, and a priori geological information available for the region under study can reduce this error. Areas of practical application of a contactless electromagnetic geothermometer are outlined.     

Impact of space energetic particles on the Earth’s atmosphere (a review)

The state of the Earth??s upper atmosphere is formed with the participation of impacts by energetic particles, such as galactic cosmic rays, protons of solar proton events, and precipitation of relativistic electrons. Changes in the neutral composition and the thermal and dynamical regime of the upper atmosphere during periods of disturbances caused by the influence of energetic particles are considered.     

Guiding MF waves from the Earth’s surface into space

The insufficiently known phenomenon of MF-wave propagation from the Earths surface through the magnetosphere (guiding) to the conjugate hemisphere and back to the transmitter has been experimentally studied. Computer modelling fulfilled on the basis of ray tracing showed that guiding was possible only from area of the main ionospheric trough. The effect of MF guiding is most useful for the diagnostics of the plasmapause, poleward edge of the trough, the diffuse precipitation boundary and so on.