Single-impulse transfers from orbits of artificial satellites to orbits around <Emphasis Type="Italic">L</Emphasis><Subscript>1</Subscript> or <Emphasis Type="Italic">L</Emphasis><Subscript>2</Subscript> libration points

In the context of the restricted circular three-body problem a method for constructing families of periodic orbits is described. Each orbit contains a segment of transfer from artificial satellite orbit of a smaller body to an orbit around L ₁ or L ₂ points of the Sun-Earth and Earth-Moon systems, a segment of multiple flyby of this libration point, and a segment of return to the artificial satellite orbit. Dependences of velocities at the pericenter on the pericenter radius are given.     

Quantitative characteristics of long-term changes in parameters of the upper atmosphere of the earth over the 1966–1992 period

On the basis of the long series of mass-spectrometer measurements conducted in rocket experiments during 1966–1992 period, long-term changes in the structural parameters of the upper atmosphere within the 100–160 km height interval at equatorial, middle, and high latitudes of the Northern Hemisphere of the Earth are quantitatively estimated. At all latitudes statistically significant negative trends are revealed in the turbopause height, temperature of the neutral atmosphere, and atomic oxygen concentration. Since the contribution to the obtained quantitative estimates of the trends caused by long-term solar-induced factors does not exceed 15–20%, a conclusion is drawn on the anthropogenic nature of the changes having occurred in the upper atmosphere.     

A study of long-term climatology of ionospheric irregularities by using GPS phase fluctuations at the Brazilian longitudes

We have examined the ionospheric plasma irregularities that were recorded by using three ground-based receivers of the global positioning system (GPS) located at Brazilian longitudes during the period of a complete solar cycle, 1995–2005. The statistic results show that ionospheric irregularities are very easy to occur in December solstice months but rare to occur in June solstice months. Besides, the occurrence rates of irregularities in both December and June solstice months are little dependent on solar activity. However, in equinoctial months, the development of irregularities is obviously dependent on solar activity. There is a new finding in this study that if strong irregularities are distinguished from moderate ones, their occurrence rates would increase with solar activity during the December solstice months.     

Ballistics of a fragmenting meteor body with allowance made for ablation in the non-isothermal atmosphere. II

The second part of the work is devoted to studying the motion of fragmenting meteor bodies with ablation by fragments in a planet’s atmosphere, taking into account its non-isothermal character in altitude. The mechanical fragmentation of a meteoroid under the action of aerodynamic drag is considered in the context of statistical strength theory. An analytical solution for ballistics of a fragmenting body is obtained at a constant parameter of ablation. A theoretical analysis of the derived regularities is made and an example of their usage in the problem of a comet-asteroid hazard is presented.     

On the motions of RHESSI flare footpoints

The footpoint motions of flare hard X-ray (HXR) sources are directly related to the reconnection scenario of a solar flare. In this work, we tried to extract the information of footpoint motions for a number of flares observed with RHESSI. We found that the RHESSI flare results of the footpoint motions strongly support the classification proposed from the observations of YOHKOH/HXT. Furthermore, it is found that a flare can consist of two types of footpoint motions. We discussed the connections of the footpoint motions with the two-dimensional reconnection models.     

Nighttime ionosphere–thermosphere coupling observed during an intense geomagnetic storm

The electrodynamics of the ionosphere in the tropical region presents various scientific aspects, which remain subject of intensive investigations and debates by the scientific community. During the year 2002, in a joint project between the Universidade do Vale do Paraíba (UNIVAP) and Universidade Luterana do Brasil (ULBRA), a chain of three Canadian Advanced Digital Ionosondes (CADIs) was established nearly along the geomagnetic meridian direction, for tropical ionospheric studies, such as, changes and response due to geomagnetic disturbances and thermosphere–ionosphere coupling and the generation and dynamics of ionospheric irregularities, in the Brazilian sector. The locations of the three ionosondes stations are São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S – under the southern crest of equatorial ionospheric anomaly), Palmas (10.2°S, 48.2°W, dip latitude 5.5°S – near the magnetic equator) and Manaus (2.9°S, 60.0°W, dip latitude 6.4°N – between the geographic and geomagnetic dip equators). It should be pointed out that Palmas and Manaus are located on the opposite sides of the magnetic equator but both are south of the geographic equator. The three CADIs work in time-synchronized mode and obtain ionograms every 5 min. This configuration of the ionospheric sounding stations allowed us to study the F-region dynamics during geomagnetically disturbed period in the meridional direction. Just after the installation and testing of the three CADIs, on September 05, 2002 a coronal mass ejection (CME) left the Sun and about 2 days after the CME left the Sun, it reached the Earth’s magnetosphere and complex and multi step events took place during the period September 07–09. In the study we note that the equatorial stations located north (Manaus, dip latitude 6.4°N) and south (Palmas, dip latitude 5.5°S) of the dip equator presented significant F-layer height asymmetries during the storm main phase. In addition, the low-latitude station SJC (dip latitude 17.6°S) presented decrease in the F-layer densities (negative phase), whereas Palmas presented increase in the F-layer densities (positive phase) during the main phase. This was followed by positive phase at both the stations. During the first night of the recovery phase a strong formation and evolution of large-scale ionospheric irregularities (equatorial spread-F (ESF)) was observed, but on the second night of the recovery phase, there was strong and almost simultaneous sporadic E (Es) formation at all three stations. During the presence of Es, spread-F formation is not observed, indicating the suppression of spread-F, possibly by sporadic E.     

Two dimensional simulation of amplitude modulated electron plasma waves

Highly modulated waves near electron plasma frequency with both parallel and perpendicular polarization have been observed near diffusion region at dayside and in the tail region. In this paper, two dimensional Particle-In-Cell (PIC) simulation was performed to study the possible generation mechanism of these modulated electron plasma waves. It is shown that weak beam instability could generate the modulated Langmuir wave and the ambient magnetic field plays an important role in the formation of modulation. When the weak beam has loss cone distribution, highly modulated upper hybrid waves are generated and propagate with large angle to the ambient magnetic field. The properties of these modulated waves are discussed and compared with observations.     

Multi-frequency doppler radio sounding of the ionosphere in the “Equatorial trigger” experiment

Results of processing the data of multi-frequency Doppler sounding of the low-latitude ionosphere are presented. Interesting features in the behavior of time variations of the Doppler frequency shift are found. These features are interpreted as manifestations of wave disturbances in the ionospheric plasma density.     

Observations of March 29, 2006 solar eclipse in the radio range at wavelengths of 3.2 and 4.9 cm

We present observations and processing of the March 29, 2006 solar eclipse data at the radio telescopes RT-3 (λ = 4.9 cm) and RT-2 (λ = 3.2 cm) of the Kislovodsk Solar Station of the Pulkovo Astronomical Observatory of RAS. Registration of the emission flux was conducted by electron method with a time resolution of 0.5 s. Compact sources on the solar disk are identified, and the contribution of coronal holes into the integral flux is determined. Comparisons to observations in the optical and X-ray ranges are performed. The intensity of sources behind the solar limb is estimated. The ratio of the intensity of residual radiation in the maximum phase to the solar emission before the eclipse was equal to 3.7 and 5.9% for 3.2 and 4.9 cm, respectively.