Chaos theory and radio emission

The application of chaos theory has become popular to understand the nature of various features of solar activity because most of them are far from regular. The usual approach, however, that is based on finding low-dimensional structures of the underlying processes seems to be successful only in a few exceptional cases, such as in rather coherent phenomena as coronal pulsations. It is important to note that most phenomena in solar radio emission are more complex. We present two kinds of techniques from nonlinear dynamics which can be useful to analyse such phenomena:

1. Fragmentation processes observed in solar spike events are studied by means of symbolic dynamics methods. Different measures of complexity calculated from such observations reveal that there is some order in this fragmentation.
2. Bursts are a typical transient phenomenon. To study energization processes causing impulsive microwave bursts, the wavelet analysis is applied. It exhibits structural differences of the pre- and post-impulsive phase in cases where the power spectra of both are not distinct.

     

Processing/analysis capabilities for data acquired with hyperspectral spaceborne sensors

The Imaging Spectrometer Data Analysis System (ISDAS) is being developed by the Canada Centre for Remote Sensing and MacDonald Dettwiler and Associates on Sun Microsystems SPARC workstations using the Application Visualization System (AVS) software package to meet the requirements for efficient processing and analysis of hyperspectral data acquired with airborne as well as future spaceborne sensors. Various visualization tools have been developed for rapid exploratory analysis together with preprocessing and information extraction tools for numerical analysis. Linkages to a spectral database and a conventional image analysis system were established to support the analysis. ISDAS is being used for multidisciplinary applications development in areas such as agriculture, environment, and exploration geology using physically based analysis approaches to retrieve information from hyperspectral data. This continuing effort, in collaboration with industry will lead to streamlined procedures that are important to take hyperspectral satellite remote sensing towards an operational mode.     

Coastal salinity measurement using a Doppler Radiometer

Coastal salinity is characterised by large and variable salinity contrasts on relatively small scales. Measurements of salinity at a resolution compatible with these coastal regions on a regular basis would provide a rich source of information that could be used for a number of applications that have a fundamental bearing on the world’s lifestyle. Doppler radiometry offers an approach to capture such measurements, as it reduces the number of required antennas needed to form an image, compared with an Interferometer type instrument.     

Certain System Aspects of the Double-Sided Cyclo-Converter

A philosophy for the improvement of the extraction of controlled dc power from a polyphase ac supply line is presented. Extension of this philosophy for the interface of synchronous polyphase networks is briefly indicated. The needed kilovolt-ampere capacity of the supply line is reduced to nearly two thirds of the capacity needed for conventional controlled ac/dc converter systems. The new system requires only a small fraction of the physical weight of conventional converters. The improvements are derived from the interposition of a modulated high-power frequency carrier between the linked systems for the purpose of reconciliation of their conflicting characteristics. The harmonic content of the ac-phase currents is greatly reduced. The system operates with internal frequencies near 10 kHz; efficiencies in the upper nineties have been attained with this type of converter.     

IMF effect on ionospheric trough occurrence at equinoxes

Previous observations have shown that there is a relationship between the F region trough and both B_z and B_y components of the interplanetary magnetic field (IMF). Since IMF governs the polar cap convection, we investigate here if this relationship can be explained by means of polar cap convection. The study is limited to equinox seasons. The poleward and equatorward edges of the trough are determined from satellite tomographic observations and their locations are plotted in magnetic coordinates together with the convection pattern given by Papitashvili and Rich [Papitashvili, V.O., Rich, F.J. High-latitude ionospheric convection models derived from DMSP ion drift observations and parameterized by the IMF strength and direction. J. Geophys. Res. 107, 2002, doi:10.1029/2001JA000264] using IMF measurements coincident with trough observations. The results indicate a close relationship between the troughs and convection. Most of the troughs are seen within the dusk cell and the pattern of trough observations rotates with the convection pattern, when B_y changes its sign. More dayside troughs are observed when B_z is negative than in the opposite case, i.e. fast convective flow favours the dayside trough occurrence. Nightside troughs are observed more frequently when B_y is negative. In both evening and morning sectors the trough is situated close to the edges of convection cells, which partly contradicts previous results showing that the troughs are associated with the convection reversal. It is concluded that plasma convection has an important role in trough generation, although the effect of a strong electric field and other mechanisms like precipitation certainly have a role of their own.     

Trojans in habitable zones

With the aid of numerical experiments we examined the dynamical stability of fictitious terrestrial planets in 1:1 mean motion resonance with Jovian-like planets of extrasolar planetary systems. In our stability study of the so-called "Trojan" planets in the habitable zone, we used the restricted three-body problem with different mass ratios of the primary bodies. The application of the three-body problem showed that even massive Trojan planets can be stable in the 1:1 mean motion resonance. From the 117 extrasolar planetary systems only 11 systems were found with one giant planet in the habitable zone. Out of this sample set we chose four planetary systems--HD17051, HD27442, HD28185, and HD108874--for further investigation. To study the orbital behavior of the stable zone in the different systems, we used direct numerical computations (Lie Integration Method) that allowed us to determine the escape times and the maximum eccentricity of the fictitious "Trojan planets."