Comparing two models of the Earth''s magnetosphere

The existence of a multiplicity of models of the Earth's magnetosphere raises the question: when are two of them equivalent in representing the real magnetosphere? The isomorphism of any two models of the Earth's magnetosphere is defined in terms of magnetic field characteristics. To assess to what degree empirical models are isomorphic with physical ones, two magnetospheres are compared: the magnetosphere of Mead and Fairfield [1975] and the physical magnetosphere proposed by Buneman, [1993]. Parameters realizing the isomorphism are found for the Buneman magnetosphere and the distribution in space of magnetic field characteristics are presented for both models.     

Densities from the CACTUS accelerometer as an external test of the validity of the thermospheric models

Total density data were obtained from the accelerometer CACTUS on board of CASTOR-D5B 1975-39A. Numerous and precise data were obtained between 250km and 600km altitude in the equatorial region (±30° latitude) for a period extending from May 1975 (minimum of solar activity) to February 1979 (already important solar activity). Since CACTUS data have not yet been used for the construction of empirical thermospheric models, a significant part of the data file is compared with several thermospheric models in order to provide an external test of the reliability of such models. Standard deviations of the order of 20% are apparent. The most significant differences extend over a few weeks and cannot be represented by the geophysical indices as they are presently used in the empirical models. Such an experimental fact suggests that the mathematical and physical aspects of the empirical models should be refined in order to achieve a better representation of physical reality.     

Models of the structure of the atmosphere of Venus from the surface to 100 kilometers altitude

From a critical comparison and synthesis of data from the four Pioneer Venus Probes, the Pioneer Venus Orbiter, and the Venera 10, 12, and 13 landers, models of the lower and middle atmosphere of Venus are derived. The models are consistent with the data sets within the measurement uncertainties and established variability of the atmosphere. The models represent the observed variations of state properties with latitude, and preserve the observed static stability. The rationale and the approach used to derive the models are discussed, and the remaining uncertainties are estimated.     

The contributions of the incoherent scatter radar technique to the development of thermospheric models

The contributions of the incoherent scatter radar technique to the development of thermospheric models is traced from the development of the radar technique in 1958. Emphasis is given to the qualitative information regarding thermospheric processes and behavior provided by the radar studies and the role that these results have played in the structural development of thermospheric models. The complementary nature of radar and satellite data in the development of recent models is stressed. In addition, a summary of pertinent radar developments over the past two years is presented. Primary among these are measurements made by high-latitude radars, multi-radar coordinated observations, the establishment of an incoherent scatter radar data base, and publication of a number of studies concerning high-latitude measurements, solar-cyle maximum results, long-term data sets, and lower thermosphere tides.     

Description of the mean behaviour of ionospheric plasma temperatures

A status report on the empirical modeling of ionospheric electron and ion temperatures is given with special emphasis on the models used in the International Reference Ionosphere (IRI).Electron temperature models have now reached a state where reliable prediction of the mean altitudinal, latitudinal and diurnal variations is possible. These models are largely based on satellite measurements, but comparisons with incoherent scatter radar measurements have shown excellent agreement. Variations with season and magnetic and solar activity seem to be small and are not yet included consistently in these models.Similar to the electron temperature, the ion temperature shows the largest variations with altitude, latitude and local time. But due to the larger mass, these variations are smoother and more steady in the case of the ions and therefore easier to model. Nevertheless, very few ion temperature models exist. The IRI model takes advantage of the observed concurrence of the ion temperature with the neutral temperature at low altitudes and with the electron temperature at high altitudes.     

The physics of the FLUKA code: Recent developments

FLUKA is a Monte-Carlo code able to simulate interaction and transport of hadrons, heavy ions and electromagnetic particles from few keV (or thermal neutron) to cosmic ray energies in whichever material. The highest priority in the design and development of the code has always been the implementation and improvement of sound and modern physical models. A summary of the FLUKA physical models is given, while recent developments are described in detail: among the others, extensions of the intermediate energy hadronic interaction generator, refinements in photon cross sections and interaction models, analytical on-line evolution of radio-activation and remnant dose. In particular, new developments in the nucleus–nucleus interaction models are discussed. Comparisons with experimental data and examples of applications of relevance for space radiation are also provided.     

Status of the Hard X-ray Modulation Telescope Project

The Hard X-ray Modulation Telescope (HXMT) is China's first astronomical satellite. It will perform a broad band (1-250keV) scan survey and do pointed observations of X-ray sources to study their spectra and multi-wavelength temporal properties. The pre-flight models of the satellites have been finished, and the flight models are in production. The expected launch date of HXMT is in late 2015.      

The accuracy of present models of the high altitude polar magnetosphere

The Polar satellite has explored the high-latitude, high-latitude magnetosphere out to 9 Earth radii (Re). The magnetic field data returned from this mission can be used both to provide data for new empirical models and to test existing models. Tests include comparing the observed location of the polar cusp with its position in the empirical models and comparing the strength of the magnetic field in the surrounding region. Near the cusp the magnetosphere is quite sensitive to solar wind conditions. In particular the energy density of the cusp plasma depends on the pressure of the solar wind applied to the interface of the cusp and the sheath. The applied pressure in turn depends on the shape of the magnetopause and the orientation of that interface, both controlled by the direction of the interplanetary magnetic field. Magnetohydrodynamic (MHD) models provide a coarse picture of the magnetosphere at high latitudes. While generally quite realistic, these too require testing against observations because even the MHD models must make some simplifying assumptions.     

The influence of radiative cooling and turbulence on the heat budget of the thermosphere

Numerical models of the thermal budget of the Earth's upper atmosphere in the height range of 90–500km are developed. The main sources and sinks of energy including infra-red radiative cooling by vibrational-rotational bands of NO, CO₂, OH and O₃ as well as heating and cooling arising from dissipation of turbulent energy and eddy heat transport are taken into account. The calculated temperature and density height profiles are in good agreement with the respective profiles from CIRA 72 and Jacchia 1977 models. It is shown for the models considered that IR-radiative cooling by CO₂ and NO in the 15μ and 5.3μ bands, not eddy turbulence provides the major loss of heat from 90 to 180km.     

Eccentric dipole approximation of the geomagnetic field: Application to cosmic ray computations

A comparison of the full IGRF model of the geomagnetic field with two simplified models, the truncated IGRF and the eccentric dipole model, is performed. The simplified models were found to provide a reasonable approximation for the large scale geomagnetic field distribution. In the application of the simplified geomagnetic models to the shielding of cosmic rays in the magnetosphere as quantified via the geomagnetic cut-off rigidity, the eccentric dipole and the truncated IGRF provide a good large scale view. The use of the simplified model does not introduce any additional systematic errors at the global scale but may be a source of moderate uncertainty at the regional scale in the tropical Atlantic region. This study quantitatively validates the use of such simplified geomagnetic models when describing the shielding of cosmic rays in the magnetosphere.     

Modelling the plasmasphere for the international reference ionosphere

The paper discusses how profiles of electron and/or ion distributions that are produced by two different computer models can be smoothly coupled together. The first of these models is the empirical International Reference Ionosphere which produces a vertical profile of ionospheric parameters up to an altitude of 1000 km. The second is a physically-based, diffusive equilibrium model of the plasmasphere based upon the theoretical work of Angerami and Thomas /1/, in which plasma is constrained to move parallel to the Earth's magnetic field lines. Some problems associated with this work are considered, as are some initial results.     

To the problem on the reliability of solar energetic proton flux models

This work analyses basic issues of conformity of the most well-known models of solar energetic particles (SEP) fluxes to the experimental data. It is shown, that the postulates on neglecting SEP fluxes in quiet Sun years and on invariability SEP fluxes in active Sun years, underlying some models, contradict the experimental data.     

On the stabilizing effect of Solar Radiation Pressure in the Earth-Moon system

Solar sails change the natural dynamics of systems: Trajectories that are driven by gravitational forces can be displaced and changed because of the effect of Solar Radiation Pressure (SRP). Moreover, if the lightness number of the sail is large enough, the instability of certain orbits can be diminished and even removed. In this paper we modify two models for the motion of a probe in the Earth-Moon system that include the effect of Sun’s gravity to take also into account the effect of SRP. These models, the Bicircular Problem (BCP) and the Quasi-Bicircular Problem (QBCP), are periodic perturbations of the Earth-Moon Restricted Three Body Problem (RTBP). The models are modified to consider the effect of the SRP upon a solar sail. We provide examples of periodic orbits that are stabilized (or made less unstable) due to the effect of SRP.     

Comparison of methods for the determination of key reactions in chemical systems: Application to Titan’s atmosphere

A new paradigm is emerging in the field of photochemistry modeling in giant planets and Titan atmospheres. The emphasis is placed on the accurate predictions of the models and the quantification of their uncertainties. In order to improve photochemical models predictions, it is necessary to identify in chemical schemes the key reactions that should be studied in priority at conditions relevant to planetary atmospheres.     

Aerosols within the world climate research programme

Based on the findings of the meeting of JSC experts on “Aerosol and Climate” (Geneva, 27–31 October 1980) the general research strategy consisting of three phases will be presented. The three phases are: Phase I: Sensitivity tests with available models Phase II: Improvement of climate models and data bases Phase III: Development of advanced climate models with internal aerosol generation and regulation processes. COSPAR's role within this research strategy is outlined.     

Animal models for the study of the effects of spaceflight on the immune system.

Animal models have been used to determine the effects of spaceflight on the immune system. Rats and rhesus monkeys have been the primary animals used for actual space flight studies, but mice have also been utilized for studies in ground-based models. The primary ground based model used has been hindlimb unloading of rodents, which is similar to the chronic bed-rest model for humans. A variety of immune responses have been shown to be modified when animals are hindlimb unloaded. These results parallel those observed when animals are flown in space. In general, immune responses are depressed in animals maintained in the hindlimb unloading model or flown in space. These results raise the possibility that spaceflight could result in decreased resistance to infection in animals.     

耀斑脉冲相半经验模型

本文在文献[9]的基础上,通过增加二个时刻的模型计算,给出了更完整的1983年2月3日2B级耀斑脉冲相色球半经验模型,从而进一步描述了脉冲相色球物理过程,并对耀斑动力学参量及能量过程作了初步讨论。      

Semi-empirical model of middle atmosphere wind from the ground to the lower thermosphere

During recent years, special attention has been paid to understanding the background circulation of the middle atmosphere. Particularly in the mesosphere/lower thermosphere (MLT) region, this has involved including data from a range of new radar measurements. It has also involved the comparison of existing empirical middle atmosphere wind models, such as CIRA-86 and HWM-93 to the new data. This has led to the construction of empirical models of MLT winds such as the Global Empirical Wind Model (GEWM). Further investigations are aimed at the construction of new empirical and semi-empirical wind models of the entire middle atmosphere including these new experimental results. The results of a new wind climatology (0–100 km) are presented here, based upon the GEWM, a reanalysis of stratospheric data, and a numerical model which is used to fill the gap between data from the stratospheric and MLT regions.