First results from UVCS/SOHO

We present here the first results obtained by the Ultraviolet Coronagraph Spectrometer (UVCS) operating on board the SOHO satellite. The UVCS started to observe the extended corona at the end of January 1996; it routinely obtains coronal spectra in the 1145 Å – 1287 Å, 984 Å – 1080 Å ranges, and intensity data in the visible continuum. Through the composition of slit images it also produces monocromatic images of the extended corona. The performance of the instrument is excellent and the data obtained up to now are of great interest. We briefly describe preliminary results concerning polar coronal holes, streamers and a coronal mass ejection, in particular: the very large r.m.s. velocities of ions in polar holes (hundreds km/sec for OVI and MgX); the puzzling difference between the HI Ly- image and that in the OVI resonance doublet, for most streamers; the different signatures of the core and external layers of the streamers in the width of the ion lines and in the OVI doublet ratio, indicating larger line-of-sight (l.o.s.) and outflow velocities in the latter.     

A superposed epoch study of the effects of solar wind stream interface events on the upper mesospheric and lower thermospheric temperature

The response of mesosphere and lower thermosphere (MLT) temperature to energetic particle precipitation over the Earth’s polar regions is not uniform due to complex phenomena within the MLT environment. Nevertheless, the modification of MLT temperatures may require an event-based study to be better observed. This work examines the influence of precipitation, triggered by solar wind stream interfaces (SI) event from 2002 to 2007, on polar MLT temperature. We first test the relationship between the ionospheric absorption measured by the SANAE IV (South African National Antarctic Expedition IV) riometer and the layer of energetic particle precipitation from POES (Polar Orbiting Environmental Satellites). The combined particle measurements from POES 15, 16, 17 and 18 were obtained close in time to the pass of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature retrieval. Here, a superposed epoch technique is described and implemented to obtain average temperature profiles during SI-triggered particle precipitation. The superposed epoch average shows no significant temperature decrease below 100 km prior to the onset of SI-triggered precipitation, whereas a clear superposed average temperature decrease is observed at 95 km after the SI impact. A case study of SI event also yields similar observations. Results indicate that cooling effects due to the production of mesospheric odd hydrogen might be major contributors to temperature decrease under compressed solar wind stream.     

Updated TUS space fluorescence detector for study of UHECR

The TUS (Tracking Ultra-violet Set up) space fluorescence detector has to be launched in 2010 as a separated platform in Foton (Bion) mission prepared by the Samara enterprise. This detector was designed for another satellite and the updated variant of the TUS detector for a new platform is presented. The data on UV glow of the atmosphere obtained in operation of one pixel of the TUS detector on board the Moscow State University “Universitetsky-Tatiana” satellite was taken into account in design of the updated TUS detector. The data on UV transient flashes registered in “Universitetsky-Tatiana” mission are of special interest. Electronics of the TUS detector able to select and register different types of UV events in the atmosphere is presented.     

Population dynamics of transgenic strain Escherichia coli Z905/pPHL7 in freshwater and saline lake water microcosms with differing microbial community structures.

Populations of Escherichia coli Z905/pPHL7, a transgenic microorganism, were heterogenic in the expression of plasmid genes when adapting to the conditions of water microcosms of various mineralization levels and structure of microbial community. This TM has formed two subpopulations (ampicillin-resistant and ampicillin-sensitive) in every microcosm. Irrespective of mineralization level of a microcosm, when E. coli Z905/pPHL7 alone was introduced, the ampicillin-resistant subpopulation prevailed, while introduction of the TM together with indigenous bacteria led to the dominance of the ampicillin-sensitive subpopulation. A high level of lux gene expression maintained longer in the freshwater microcosms than in sterile saline lake water microcosms. A horizontal gene transfer has been revealed between the jointly introduced TM and Micrococcus sp. 9/pSH1 in microcosms with the Lake Shira sterile water.     

Periodic motions of a nearly dynamically symmetric satellite in the neighborhood of hyperboloidal precession

The motion of a satellite close to a dynamically symmetric solid body in a Newtonian gravitational field over a circular orbit is studied. The system of differential equations describing the body’s motion is close to a system with cyclic coordinate. New classes of periodic motions are constructed in the neighborhood of a known partial solution to an unperturbed problem, hyperboloidal precession of a dynamically symmetric satellite. In the resonance case, when the ratio of one frequency of small oscillations of a reduced system with two degrees of freedom in the neighborhood of a stable equilibrium position to the frequency of cyclic coordinate variation is close to an integer number, there exist one or three families of periodic motions that are analytic in terms of fractional powers of a small parameter. A study of stability of these motions was performed with the help of KAM (Kolmogorov-Arnold-Moser) theoty. Faling the described resonance there exists a unique family of periodic motions that is analytic in terms of integer powers of a small parameter. The check-up of stability of these motrons was carried out. We distinguished the cases of parametric resonance, resonances of the third and fourth orders, and a non-resonant case. In the resonance cases our study relies on well-known results on stability of Hamiltonian systems during resonances [1]. In the non-resonant case we use the KAM theory [2].     

On Processing Optical Images Propagated Through the Atmosphere

The problem of how to process optical images that have propagated through a turbulent atmosphere is considered. It is assumed that either the object or its (free-space) scattered field at the receiving aperture is known, except for unknown parameters that are to be estimated. Isotropic and homogeneous turbulence as discussed by Tatarski and Chernov is assumed. It is assumed that a very short (in time) reception is made, that the turbulence-induced complex phase errors are either small or have a correlation distance short relative to the receiving aperture extent, and that the object is within an isoplanatic region. The method of maximum likelihood (ML) is used as a criterion; its applicability is discussed. The ML image-processing structure is found and is nonlinear. Asymptotic cases are examined; among other conclusions, it is shown that the ML processing of independent receptions is more complex than an ML processing of the sum of the receptions. A coherent optical system that realizes the ML image processor is described; it includes the capability to generate the scattered field. Simplifications are pointed out.     

Geostationary orbit plasma pressure variations according to gorizont satellite data

Plasma and energetic particles pressure distribution is studied using data from the plasma and energetic particle experiment (0.1 –133 keV) onboard the Gorizont-35 geostationary satellite for the period from 11 to 25 March 1992. The analysed period consists of relatively quiet time, small geomagnetic storms, SC and the time of the northern orientation of the IMF. The calculations show that the basic contribution to the total particle pressure was made by ions at the energy from 0.1 to 12.4 keV. The derived average value of the calculated pressure (≈1 nPa) points to the important role of the geostationary orbit plasma population in the formation of the magnetopause pressure balance and of the near-Earth magnetic field distortion.     

Improving DORIS geocenter time series using an empirical rescaling of solar radiation pressure models

Even if Satellite Laser Ranging (SLR) remains the fundamental technique for geocenter monitoring, DORIS can also determine this geophysical parameter. Gobinddass et al. (2009) found that part of the systematic errors at 118 days and 1 year can be significantly reduced by rescaling the current solar radiation pressure models using satellite-dependent empirical models. Here we extend this study to all DORIS satellites and propose a complete set of empirical solar radiation parameter coefficients. A specific problem related to SPOT-5 solar panel realignment is also detected and explained. New DORIS geocenter solutions now show a much better agreement in amplitude with independent SLR solutions and with recent geophysical models. Finally, the impact of this refined DORIS data strategy is discussed in terms of Z-geocenter monitoring as well as for other geodetic products (altitude of high latitude station such as Thule in Greenland) and Precise Orbit Determination. After reprocessing the full 1993.0-2008.0 DORIS data set, we confirm that the proposed strategy allows a significant reduction of systematic errors at periods of 118 days and 1 year (up to 20 mm), especially for the most recent data after 2002.5, when more DORIS satellites are available for geodetic purposes.