Statistical analysis of the total electron content observed at 23°S in the Brazilian sector

The vertical total electron content (VTEC) time series obtained at São José dos Campos (23.2°S, 45.9°W), Brazil, were statistically analyzed to study the low latitude ionosphere in the Brazilian sector during the year of 2006 (a period of low solar activity). Statistical analysis showed that Probability Density Functions (PDFs) and kurtosis have an intermittent behavior on small-scales (periods from minutes to one day) and presence of two functions on large-scales (periods from 3 to 30 days). The skewness result suggests the presence of some kind of waves due to the action of tropospheric sources (lower atmospheric origin). Results obtained by wavelet transform show strong oscillations with scale-sizes between 3 and 30 days, possibly associated with the planetary oscillations. According to these statistical and wavelet analyses we conjecture that there exist two important factors regarding the ionospheric effects: one factor is due to turbulent states found in small scales and the other factor consists in a more or less deterministic state provided by planetary waves (3–16 days or full solar rotation (27–28 days)). Further, these strong oscillations were also noted in multifractal analysis. We found a decrease of multifractality degree of the same scale-sizes.     

Model for induced ionization by galactic cosmic rays in the Earth atmosphere and ionosphere

The ionization profiles produced by galactic cosmic rays in the Earth atmosphere and ionosphere are obtained on the basis of Monte Carlo simulations. Cascade processes in the atmosphere are simulated using CORSIKA 6.52 code with FLUKA 2006 and QGSJET II hadronic interaction subroutines. Proton induced showers are considered using a realistic atmospheric model (US Standard Atmosphere). The energy deposit from different components is taken into account, namely electromagnetic, hadron and muon components. The curvature of the atmosphere is considered in the computer code. On the basis of the computed ionization yield function the ion pair production rate in the atmosphere is obtained for different conditions and locations. The model is applicable to the entire atmosphere, from ground level to upper atmosphere. Several applications of the obtained results are discussed. The Monte Carlo simulation model considers nuclear interactions below the altitude of 35 km. It is compared with analytical–numerical electron production rate model. The latter model which takes into account the electromagnetic interactions above altitudes of 35 km has two main regions of application: above 50 km (thin target model) and between 35 and 50 km (intermediate target model). A good agreement between the CORSIKA results and analytical–numerical model results is found above altitude of 35 km.     

Training astronauts using three-dimensional visualisations of the International Space Station

Recent advances in personal computer technology have led to the development of relatively low-cost software to generate high-resolution three-dimensional images. The capability both to rotate and zoom in on these images superposed on appropriate background images enables high-quality movies to be created. These developments have been used to produce realistic simulations of the International Space Station on CD-ROM. This product is described and its potentialities demonstrated. With successive launches, the ISS is gradually built up, and visualised over a rotating Earth against the star background. It is anticipated that this product's capability will be useful when training astronauts to carry out EVAs around the ISS. Simulations inside the ISS are also very realistic. These should prove invaluable when familiarising the ISS crew with their future workplace and home. Operating procedures can be taught and perfected. "What if" scenario models can be explored and this facility should be useful when training the crew to deal with emergency situations which might arise. This CD-ROM product will also be used to make the general public more aware of, and hence enthusiastic about, the International Space Station programme.     

Wave perturbations in the MLT at high northern latitudes in winter,observed by two SATI instruments

To investigate the Mesosphere and Lower Thermosphere (MLT) region, several ground-based instruments called SATI (Spectral Airglow Temperature Imager) were designed and built to measure airglow emission and temperature in the upper mesosphere. One SATI instrument was installed at Resolute Bay (74.7°N, 94.9°W) and has monitored the polar MLT region since November, 2001. In October 2007 another SATI instrument was installed at Eureka (80.0°N, 86.3°W) at the Polar Environment Atmospheric Research Laboratory (PEARL) as part of the Canadian Network for the Detection of Atmospheric Change (CANDAC) project. SATI is a spatial scanning Fabry–Perot spectrometer measuring column emission rates for several rotational lines of OH and O₂ airglow at 87 and 94 km height. The rotational temperatures are inferred from the ratios of these lines. The measurements are divided into 12 sectors with an annular field of view. The phase differences between the sectors yield information on the horizontal atmospheric wave direction and wavelength. Horizontal perturbations of 2–8 h period have correlatively been observed and investigated at both locations. Short-periodic oscillations identified as gravity waves with periods between 2 and 8 h propagate in southward and eastward directions, but in opposite directions in some cases. The wave propagation characteristics are often different at the two locations; the relationship with the lower mean wind is considered.     

Electric field and ion density anomalies in the mid latitude ionosphere: Possible connection with earthquakes?

The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospherical anomalies. We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere; these ionospheric anomalies have been proposed by Gousheva et al. [Gousheva, M., Glavcheva, R., Danov, D., Angelov P., Hristov, P., Influence of earthquakes on the electric field disturbances in the ionosphere on board of the Intercosmos-Bulgaria-1300 satellite. Compt. Rend. Acad. Bulg. Sci. 58 (8) 911–916, 2005a; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Observation from the Intercosmos-Bulgaria-1300 satellite of anomalies associated with seismic activity. In: Poster Proceeding of 2nd International Conference on Recent Advances in Space Technologies: Space in the Service of Society, RAST ‘2005, June 9–11, Istanbul, Turkey, pp. 119–123, 2005b; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Satellite monitoring of anomalous effects in the ionosphere probably related to strong earthquakes. Adv. Space Res. 37 (4), 660–665, 2006]. This paper presents new results from observations of the quasi-static electric field and ion density on board INTERCOSMOS-BULGARIA-1300 satellite in the mid latitude ionosphere above sources of moderate earthquakes. Data from INTERCOSMOS-BULGARIA-1300 satellite and seismic data (World Data Center, Denver, Colorado, USA) for magnetically quiet and medium quiet days are juxtaposed in time-space domain. For satellite’s orbits in the time period 15.09–01.10.1981 an increase in the horizontal and vertical components of the quasi-static electric field and fluctuations of the ion density are observed over zones of forthcoming seismic events. Some similar post effects are observed too. The emphasis of this paper is put on the anomalies which specify the mid latitude ionosphere. The obtained results contain important information because they confirm our previous results for near-equatorial and low latitude regions.     

Schumann Resonances as a Means of Investigating the Electromagnetic Environment in the Solar System

The propagation of extremely low frequency (ELF, 3 Hz to 3 kHz) radio waves and resonant phenomena in the spherical Earth-ionosphere cavity has been studied for almost fifty years. When such a cavity is excited by naturally occurring broadband electromagnetic radiation, resonances can develop if the equatorial circumference is approximately equal to an integral number of wavelengths of the propagating electromagnetic waves; these are termed Schumann resonances. They provide information not only about thunderstorm and lightning activity on the Earth, and their relation to climate, but also on the properties of the low ionosphere. Similar investigations can be performed for any other planet or satellite, provided that it has an ionosphere. There are important differences between the Earth and other celestial bodies regarding, for example, the surface conductivity, the atmospheric conductivity profile, the geometry of the ionospheric cavity, and the sources of excitation. To a first approximation, the size of the cavity defines the fundamental resonant frequency, the atmospheric electron density profile controls the wave attenuation, the nature of the sources influences the electromagnetic field distribution in the cavity, and the body surface conductivity indicates to what extent the subsurface can be explored. The frequencies and attenuation rates of the principal eigenmodes depend upon the electrical properties of the cavity. Instruments that monitor the electromagnetic environment in the ELF range on the surface, on balloons, or on descent probes provide unique information on the cavity. In this paper, we present Schumann resonance models for selected inner planets, some gaseous giant planets and a few of their satellites. We review the crucial parameters of ELF electromagnetic waves in their atmospheric cavities, namely the electric and magnetic field spectra, their eigenfrequencies, and the associated Q-factors (damping factors). Then we present important information on theoretical developments, on a general model that uses the finite element method and on the parameterization of the cavity. Next we show the distinctiveness of each planetary environment, and discuss how ELF radio wave propagation can contribute to an assessment of the major characteristics of those planetary environments.     

Interference experiments between fixed-satellite and terrestrialradio-relay services

To resolve interference problems between fixed-satellite and terrestrial radio relay services and expand coordination areas between the two services, theoretical and experimental studies were carried out. Theoretical D/U values calculation formulas between the two systems were derived, interference data from 4 GHz and 11 GHz band terrestrial radio-relay systems were obtained by a measuring system mounted on a vehicle. By comparing those results, it becomes clear that the ensemble interference reduction factors for 4 GHz and 11 GHz bands are around 20 dB, which is mixed values of attenuation and reflection from big buildings in urban areas     

高超声速脉冲风洞中带燃料的超燃冲压发动机模型试验

给出了在ITAM最近投入使用的高超声速脉冲绝热压缩风洞AT-303中进行超燃冲压发动机模型实验的结果.实验马赫数M∞≈8,运行时间τ=50~60 ms,雷诺数范围Re1∞=2.7×106~4.0×107,模型表面的边界层自然转捩.在实验中,模型中有燃料供给:把气态氢以超过化学量比率的空气燃料因子注入到燃烧室.提供了足以发生氢燃料自点燃的流动条件.测量了沿进气道楔型压缩面和整个发动机通道上的纵向压力和热流分布.所获数据与同一模型在热射流风洞IT-302M(实验马赫数M∞≈6,8,运行时间τ=100~120 ms,雷诺数范围Re1∞=(1.3~1.8)×106,进气道压缩面和侧压缩面进行了边界层转捩).结果表明:实验模型发动机在两座风洞中进行实验所获得的流态类型相同.发动机刚刚启动时,在进气道入口及其下游的发动机通道内形成超声速流.注入氢后,首先在燃烧室内形成平均流速是超声速的燃烧流动.之后,在燃烧室出口出现热拥塞现象、在进气道扩压段产生伪激波流态.在两座风洞中进行了进气道和发动机通道的流动特征试验,获得了令人满意的结果.     

Statistical properties of the IMF clock angle in the solar wind with northward and southward interplanetary magnetic field based on ACE observation from 1998 to 2009: Dependence on the temporal scale of the solar wind

Utilizing ACE satellite observations from 1998 to 2009, we performed the elaborate study on the properties of the clock angle θ_CA (arctan(By/Bz) (?90° to 90°) of the interplanetary magnetic field (IMF) in the solar wind at 1?AU. The solar wind with northward IMF (NW-IMF) and southward IMF (SW-IMF) are analyzed, independently. Statistical analysis shows that the solar wind with SW-IMF and NW-IMF has similar properties in general, including their durations, the IMF Bz and By components, and the IMF θ_CA. Then, the solar wind with NW-IMF (SW-IMF) is classified into five different temporal scales according to the duration of the NW-IMF (SW-IMF), i.e., very-short wind of 10–30?min, short-scale wind of 0.5–1?h, moderate-scale wind of 1–3?h, long-scale wind of 3–5?h, and super-long wind >5?h. Our analysis reveals that the IMF θ_CA has a distinct decrease with increase of the temporal scale of the solar wind. Next, the solar wind is classified into two groups, i.e., the high-speed solar wind (>450?km/s) and the low-speed solar wind (<450?km/s). Our analysis indicates that the IMF θ_CA depends highly on the solar wind speed. Statistically, high-speed solar wind tends to have larger IMF θ_CA than low-speed solar wind. The evolutions of the solar wind and IMF with the solar activity are further studied, revealing no clear solar variation of the IMF θ_CA. Finally, we analyze the monthly variation of the IMF θ_CA. Superposed epoch result strongly suggests the seasonal variation of the IMF θ_CA.     

CREAM: 70 days of flight from 2 launches in Antarctica

The Cosmic-Ray Energetics And Mass balloon-borne experiment has been launched twice in Antarctica, first in December 2004 and again in December 2005. It circumnavigated the South Pole three times during the first flight, which set a flight duration record of 42 days. A cumulative duration of 70 days within 13 months was achieved when the second flight completed 28 days during two circumnavigations of the Pole on 13 January 2006. Both the science instrument and support systems functioned extremely well, and a total 117 GB of data including 67 million science events were collected during these two flights. Preliminary analysis indicates that the data extend well above 100 TeV and follow reasonable power laws. The payload recovered from the first flight has been refurbished for the third flight in 2007, whereas the payload from the second flight is being refurbished to be ready for the fourth flight in 2008. Each flight will extend the reach of precise cosmic-ray composition measurements to energies not previously possible.