Dynamics of Planetary Waves in the Ionosphere as Observed from GPS Satellites

The GPS satellite data are used to study the dynamics of the ionospheric total electron content (TEC) over Central Europe in the summer season from June 23 to September 30, 1996. The TEC variations within the range of periods typical of the planetary waves were found to be nearly synchronous with the neutral wind variations in the mesosphere and with the variations in the occurrence of ionospheric sporadic layers. The observed TEC variations were interpreted as the result of penetration of energy carried by nonstationary Rossby waves to the upper atmospheric altitudes.     

Sporadic structures in equatorial ionosphere as revealed from GPS occultation data

A method for monitoring of sporadic formations in the lower ionosphere by use of the amplitude and phase variations of decimeter radio waves in the occultation trans-ionospheric link GPS satellite — LEO CHAMP satellite is described. Typical variations of the amplitude and phase of the occultation signal, caused by layered formations in the lower ionosphere, are considered. Parameters of sporadic structures measured during period of especially strong solar flashes from October 25 till November 9, 2003, are described. Results of statistical analysis of the occurrence frequency of sporadic layers, their altitude distribution, and thickness are presented. The electron density distribution in the lower ionosphere in the equatorial zone is estimated.     

Physical Prerequisites of the Antimeteoric Net Protection for Spacecraft

The problem of spacecraft protection against the impact effect of meteorites and man-made (technogenous) particles has become especially topical in connection with the necessity of long-duration flights in space. The probability of spacecraft collision with meteoric and technogenous particles has already considerably increased on the widely used, but strongly contaminated near-Earth orbits. Russian specialists (the author included) proposed to use multilayer spaced barriers for spacecraft protection as early as the beginning of the 1960s. However, further studies on decreasing the mass of antimeteoric shields are required nowadays. The safety net application is one promising approach in this respect. This paper outlines the physical prerequisites for using a net (a system of strings) as one of a package of antimeteoric shields. The simplest models of meteoric particle destruction at impact on the safety net are presented. The hydrodynamic models, as most suitable for modeling the process, are mainly analyzed. The role of the interaction of shock waves and of cumulative effects upon meteorite impact with the net is emphasized. The net is shown to play an important part in forming the nonuniform field of stresses in a meteorite even at high impact velocities, which are accompanied by phase transitions and by the generation of plasma. The role of a safety net for retaining and absorbing the momentum of a plasma cloud, formed upon the impact of meteoric particles, is considered. The advisability of applying two (or several) net barriers is substantiated. It is noted that the safety net can also be useful as a means for mitigating the action of shock waves from explosions.     

Gravitational and hydroelastic waves in thomson-delaney cells of the ocean on Jovian Moon Europa

The possibility of appearance of hydrothermal cells in the system “Ocean of Jovian Moon Europaits ice crust” was theoretically proved by R. Thomson and J. Delaney [8]. We formulated in [11] boundary value problems for planetary gyroscopic waves and gravitationally elastic waves in these cells, and the spectrum of nondivergent gyroscopic waves was numerically investigated. The present paper is a continuation of [11]. It considers the spectra of independent, purely gravitational and hydroelastic waves. The possibility of resonant excitation in Thomson-Delaney cells of gravitational and hydroelastic waves is considered.     

Planetary waves according to simultaneous observations of <Emphasis Type="Italic">GPS</Emphasis> satellites and ground-based magnetic stations

On the basis of measurements made at Japanese magnetic stations and using GPS satellites for the 12 months of 2003, a comparison of simultaneous variations of three components of the magnetic field and total electron content (TEC) was carried out in the range of the planetary waves period. The correlation analysis has shown that almost synchronous variations exist within this range of periods at the ground-based magnetometer stations and in the TEC measurements both during strong magnetic disturbances and in quiet periods. The strong magnetic disturbances could be considered as a possible independent source of ionospheric variations within the planetary waves range, while the accompanying ionospheric storms could be a possible factor changing the conductivity of the lower ionosphere plasma. In quiet periods, the correlation of magnetic variations and disturbances in TEC is caused by the direct impact of atmospheric planetary waves on the lower ionosphere and can be related to variations of ionospheric currents due to the dynamo mechanism.     

The effect of heavy ions on the spectrum of oscillations of the magnetosphere

Some issues concerning the influence of multi-ion composition of plasma on the spectrum of ultralow frequency (ULF) oscillations in the magnetosphere are analyzed. Main emphasis is made on the effects that are perceptible by analyzing the results of observations of ULF oscillations. The resonator confining ion cyclotron waves in the equatorial zone high above the Earth is considered, as well as the near-equatorial waveguide existing under the plasmasphere arch and canalizing magnetosonic waves in the azimuth direction. It is shown that the very existence of the ion-cyclotron resonator would be impossible, if only one species of ions were contained in plasma. It is emphasized that the problem of excitation of magnetosonic waves with harmonics of the gyrofrequency of O⁺ needs further investigation. The effect of heavy ions on the spectrum of Alfvén oscillations of the magnetosphere is considered. Some arguments are presented giving evidence that existence of alpha-particles in the solar wind leads to an asymmetry of the spectrum of magnetosonic oscillations in front of the Earth’s bow shock. Anomalously large asymmetry is expected at immersion of the Earth into the “plasmasphere” of the flare-associated stream of solar plasma. The general conclusion is made that even a small admixture of heavy ions can have a substantial effect on the spectrum of ULF oscillations.     

Midlatitude auroras in the south of Eastern Siberia during strong geomagnetic storms on October 29–31, 2003 and November 20–21, 2003

Preliminary results of optical observations of midlatitude auroras at the Geophysical observatory of ISTP SD RAS in the south of Eastern Siberia (52°N, 103°E) during two strong magnetic storms on October 29–31, 2003 and November 20–21, 2003 are analyzed. The results of observations are compared to similar data on midlatitude auroras observed at the geophysical observatory in previous years. The recorded maximum intensities of atmospheric emissions and accompanying solar and geophysical conditions make it possible to conclude that the analyzed midlatitude auroras in their optical manifestation can be considered as extreme events observed at midlatitudes.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 616–621.Original Russian Text Copyright © 2004 by Mikhalev, Beletsky, Kostyleva, Chernigovskaya.     

Parametric excitation of gyroscopic waves in Thomson-Delaney cells of the ocean of Jovian moon Europa

A possible mechanism (of parametric resonance type) of excitation of planetary gyroscopic waves in Thomson-Delaney cells of the ocean of Jovian moon Europa is considered. It is assumed that the basis of this mechanism is a variation of liquid depth in a cell caused by tidal oscillations under the action of gravitational perturbing influence of Galilean satellites of Jupiter. Such a model leads to a system of linear differential equations with periodic coefficients of the Hill’s type. Under some additional assumptions it changes over into a system of independent Mathieu equations. The regions of parametric resonance of this system are constructed.     

Interaction of Phobos with the Solar Wind Plasma

The interaction of Phobos with the solar wind is considered both theoretically and using the experimental data of the FGMM magnetometer that were obtained in the course of the Phobos-2mission. It is demonstrated that the ions serving as a source of excitation of magnetosonic waves can be accumulated around Phobos. Examination of the magnetometer data has shown that the observed effects of a local decrease of the magnetic field near the Phobos orbit correspond to magnetosonic waves. Observation of these effects depends on the geometry of an experiment.     

Electromagnetic sounding of planets from a low-orbiting probe

Is it theoretically possible to perform magnetotelluric sounding in order to determine the conductivity of a planet’s interior based on the registration of variable electric and magnetic fields on a low-orbiting space probe? In this case, fast magnetosonic (FMS) waves in the planetary magnetosphere can play the role of sounding waves. It has been indicated that the registration of FMS-wave impedance (the ratio of the electric and magnetic components) onboard the probe actually makes it possible to estimate the planetary conductivity for a planet with a magnetosphere and ionosphere.     

Structure of planetary disturbances of the mid-latitude ionosphere according to observations of GPS satellites

Using GPS satellites, the existence of ionospheric disturbances in the range of planetary wave periods is established based on global variations of the total electron content in the mid-latitude ionosphere in the summer months of 1990. For quasi-two-day variations, a substantial difference is found of the structure of these variations from variations with the same quasi-period in the atmosphere. In addition, it is demonstrated that the ionospheric response to quasi-seven-day atmospheric variations is a more general phenomenon than was commonly believed before. The observed variations of the total electron content are interpreted as a consequence of the modulation of tidal oscillations by planetary waves.     

The first cell membranes

Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous species. Some of these compounds are amphiphilic, having polar and nonpolar groups on the same molecule. Amphiphilic compounds spontaneously self-assemble into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to have been produced from amphiphilic compounds on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. The goal of future investigations will be to fabricate artificial cells as models of the origin of life.     

Physical and Mathematical Simulation of Electric Polarization of Low-Orbit Spacecraft under the Conditions of Hypersonic Flow by a Stream of Plasma of the Earth's Upper Ionosphere

The charging processes in the vicinity of a low-orbital spacecraft moving in the midlatitude ionosphere are considered. It is shown that the main feature of charging of such an object is its polarization. The calculation results are analyzed in the context of general theoretical concepts.     

Consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface

Possible consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface are described. The methodological basis of classification of consequences is the solution of meteor physics equations characterizing the trajectory of a body in the atmosphere, namely, the dependence of the body’s velocity and mass on the flight altitude. The solution depends on two dimensionless parameters characterizing the drag altitude and the role of mass loss by a meteoroid during its motion in the atmosphere. Depending on values of these parameters, the degree of effect on the planetary surface considerably changes. In particular, the conditions of cratering and meteorite fall on the planetary surface are obtained. The results are presented in a simple analytical form. They quite match to the real events considered in the paper. Recommendations are given on further investigations into the important problem of interaction of cosmic bodies with planetary atmospheres.     

Nonlinear Disturbances in the Ionospheric E Region under the Action of Internal Gravity Waves

We consider the influence of harmonics generated by an internal gravity wave (IGW) on the formation of nonlinear disturbances in the ionospheric E region. It is shown that the response of the lower ionosphere to the IGW propagation should be less efficient than the action of the IGW on the ionospheric F region. Nevertheless, if there are some thin layers (e.g., sporadic E layers) in the lower ionosphere, the response can be amplified; its amplitude is determined by the sharpness of the density gradient as compared with the characteristic scale of the atmosphere.     

Nitrogen fixation on early Mars and other terrestrial planets: experimental demonstration of abiotic fixation reactions to nitrite and nitrate

Understanding the abiotic fixation of nitrogen is critical to understanding planetary evolution and the potential origin of life on terrestrial planets. Nitrogen, an essential biochemical element, is certainly necessary for life as we know it to arise. The loss of atmospheric nitrogen can result in an incapacity to sustain liquid water and impact planetary habitability and hydrological processes that shape the surface. However, our current understanding of how such fixation may occur is almost entirely theoretical. This work experimentally examines the chemistry, in both gas and aqueous phases, that would occur from the formation of NO and CO by the shock heating of a model carbon dioxide/nitrogen atmosphere such as is currently thought to exist on early terrestrial planets. The results show that two pathways exist for the abiotic fixation of nitrogen from the atmosphere into the crust: one via HNO and another via NO(2). Fixation via HNO, which requires liquid water, could represent fixation on a planet with liquid water (and hence would also be a source of nitrogen for the origin of life). The pathway via NO(2) does not require liquid water and shows that fixation could occur even when liquid water has been lost from a planet's surface (for example, continuing to remove nitrogen through NO(2) reaction with ice, adsorbed water, etc.).     

High-resolution simulations of the final assembly of Earth-like planets. 2. Water delivery and planetary habitability

The water content and habitability of terrestrial planets are determined during their final assembly, from perhaps 100 1,000-km "planetary embryos " and a swarm of billions of 1-10-km "planetesimals. " During this process, we assume that water-rich material is accreted by terrestrial planets via impacts of water-rich bodies that originate in the outer asteroid region. We present analysis of water delivery and planetary habitability in five high-resolution simulations containing about 10 times more particles than in previous simulations. These simulations formed 15 terrestrial planets from 0.4 to 2.6 Earth masses, including five planets in the habitable zone. Every planet from each simulation accreted at least the Earth's current water budget; most accreted several times that amount (assuming no impact depletion). Each planet accreted at least five water-rich embryos and planetesimals from the past 2.5 astronomical units; most accreted 10-20 water-rich bodies. We present a new model for water delivery to terrestrial planets in dynamically calm systems, with low-eccentricity or low-mass giant planets-such systems may be very common in the Galaxy. We suggest that water is accreted in comparable amounts from a few planetary embryos in a " hit or miss " way and from millions of planetesimals in a statistically robust process. Variations in water content are likely to be caused by fluctuations in the number of water-rich embryos accreted, as well as from systematic effects, such as planetary mass and location, and giant planet properties.     

Planetary gyroscopic waves in Thomson-Delaney cells of the ocean of Jupiter’s moon Europa

Observational data of the Galileo mission testify that there is a possibility of existence of planetary waves in the ocean of Jupiter’s moon Europa. A model of rotating ocean is used for the analysis of dynamics of underlying wavy processes. The model uses geometrical stratification of the ocean’s icy surface into separate cells with a typical size of order of 100 km. These cells of hydrothermal nature contain liquid lenses, and the possibility of their origination was postulated and theoretically studied by P. Thomson and J. Delaney in 2001. Using the Bubnov-Galerkin method, the spectrum of natural vibrations of liquid (gyroscopic waves) in Thomson-Delaney cells was found taking into account the satellite’s rotation in a simple model of the icy crust. In order to study a possibility of resonance excitation of tidal oscillations of liquid in the cells, the dominant elements of this spectrum are compared to theoretical values of the frequencies of tide-generating forces associated with eccentricity of the orbit of the Jupiter’s moon Europa and with perturbations from other Galilean satellites of Jupiter. This allows one to discover a large number of resonances on dominant modes with periods of from 3.5 to 7 days in the Europa ocean regions, corresponding to latitudes from 30° to 70°.     

Abiotic nitrogen fixation on terrestrial planets: reduction of NO to ammonia by FeS

Understanding the abiotic fixation of nitrogen and how such fixation can be a supply of prebiotic nitrogen is critical for understanding both the planetary evolution of, and the potential origin of life on, terrestrial planets. As nitrogen is a biochemically essential element, sources of biochemically accessible nitrogen, especially reduced nitrogen, are critical to prebiotic chemistry and the origin of life. Loss of atmospheric nitrogen can result in loss of the ability to sustain liquid water on a planetary surface, which would impact planetary habitability and hydrological processes that shape the surface. It is known that NO can be photochemically converted through a chain of reactions to form nitrate and nitrite, which can be subsequently reduced to ammonia. Here, we show that NO can also be directly reduced, by FeS, to ammonia. In addition to removing nitrogen from the atmosphere, this reaction is particularly important as a source of reduced nitrogen on an early terrestrial planet. By converting NO directly to ammonia in a single step, ammonia is formed with a higher product yield (~50%) than would be possible through the formation of nitrate/nitrite and subsequent conversion to ammonia. In conjunction with the reduction of NO, there is also a catalytic disproportionation at the mineral surface that converts NO to NO? and N?O. The NO? is then converted to ammonia, while the N?O is released back in the gas phase, which provides an abiotic source of nitrous oxide.     

软着陆验证试验中月面特性模拟方法

月面特性的模拟是月面软着陆验证试验的重要设计因素。文章结合探测器的设计状态和试验需求,论述了月面特性模拟的具体要求;基于月面地形统计分布规律,实现了月面原始形貌的模拟;通过高程剔除设计和模块化组合设计,实现了对多种典型月貌的快速模拟;最后通过月表反射特性的模拟,全面满足了试验要求,并取得了良好的试验效果。文中所述的模拟方法可为我国后续行星表面探测器及着陆技术的验证提供借鉴。