Model for the VLF/LF radio signal anomalies formation associated with earthquakes

The influence of quasi-static electric field of seismic origin on the characteristics of the internal gravity waves (IGWs) in the Earth’s ionosphere is considered. The electric field in the ionosphere arises due to the injection of charged aerosols into the atmosphere, formation of an EMF in the near Earth atmosphere and perturbation of the conductive electric current in the global electric circuit. Amplification of the electric current in seismic zone is accompanied by the formation of perturbation of the lower ionosphere that affects the amplitude and phase of VLF/LF signals. The action of the electric field on the IGWs is connected with the appearance of the Ampere’s force in the ionosphere. In the spectral range of these waves the latter acts on the neutral component of the ionosphere plasma. As the result of this interaction the ionosphere starts to support the discrete spectrum of oscillations. Periods of their maximums increase as numbers of natural sequence. The existence of such peculiarities of the waves in the ionosphere is confirmed by observations.     

Comparing TOPEX TEC measurements with IRI predictions

TEC values obtained from TOPEX satellite were compared with the International Reference Ionosphere (IRI) 2001 model estimates. The present work also shows results of the IRI model with the option of a new topside electron density distribution (NeQuick model). TOPEX TEC measurements, which include years of high and middle to low solar activity (2000 and 2004), were analyzed by binning the region covered by the satellite (±66°) every five degrees of modip. In general, there is good agreement between IRI predictions and Topex measurements. Cases with large disagreements are observed at low and high latitudes during high solar activity. Comparing the model predictions using the default IRI2001 model and the NeQuick topside option show that the default IRI 2001 version represents the observed data in a more realistic way, but appears to be less reliable at high and low latitudes in some cases.     

Investigating the cellular effects of isolated radiation tracks using microbeam techniques.

Studies of the effects of radiation at the cellular level have generally been carried out by exposing cells randomly to the charged-particle tracks of a radiation beam. Recently, a number of laboratories have developed techniques for microbeam irradiation of individual cells. These approaches are designed to remove much of the randomness of conventional methods and allow the nature of the targets and pathways involved in a range of radiation effects to be studied with greater selectivity. Another advantage is that the responses of individual cells can be followed in a time-lapse fashion and, for example, processes such as "bystander" effects can be studied clearly. The microbeam approach is of particular importance in mechanistic studies related to the risks associated with exposure to low fluences of charged particles. This is because it is now possible to determine the actions of strictly single particle tracks and thereby mimic, under in vitro conditions, exposures at low radiation dose that are significant for protection levels, especially those involving medium- to high-LET radiations. Overall, microbeam methods provide a new dimension in exploring mechanisms of radiation effect at the cellular level. Microbeam methods and their application to the study of the cellular effects of single charged-particle traversals are described.     

The ozonesonde intercomparison experiment at Thumba

An Indo-Soviet collaborative experiment on Ozonesonde Intercomparison was conducted at TERLS in March 1983. Thirteen rocket ozonesondes, eleven balloon ozonesondes and seven meteorological rockets were launched from Thumba. The rocket and balloon soundings were supported by on site Dobson spectrophotometric observations, surface ozone measurements as well as measurements with a Volz type filter photometer. The programme has yielded data on ozone vertical profiles from eleven rocketsondes, seven balloon-sondes and four sets of Umkehr observations. The data is studied with a view to intercompare the various sensors.     

Structural and functional organisation of regenerated plant protoplasts exposed to microgravity on Biokosmos 9.

Preparatory experiments for the IML-1 mission using plant protoplasts, were flown on a 14-day flight on Biokosmos 9 in September 1989. Thirty-six hours before launch of the biosatellite, protoplasts were isolated from hypocotyl cells of rapeseed (Brassica napus) and suspension cultures of carrot (Daucus carota). Ultrastructural and fluorescence analysis of cell aggregates from these protoplasts, cultured under microgravity conditions, have been performed. In the flight samples as well as in the ground controls, a portion of the total number of protoplasts regenerated cell walls. The processes of cell differentiation and proliferation under micro-g did not differ significantly from those under normal gravity conditions. However, in micro-g differences were observed in the ultrastructure of some organelles such as plastids and mitochondria. There was also an increase in the frequency of the occurrence of folds formed by the plasmalemma together with an increase in the degree of complexity of these folds. In cell cultures developed under micro-g conditions, the calcium content tends to decrease, compared to the ground control. Different aspects of using isolated protoplasts for clarifying the mechanisms of biological effects of microgravity are discussed.     

The generation of DC and AC electric fields, and electron fluxes in a rocket experiment with barium injection in the auroral ionosphere

The results of an active rocket experiment with barium injection in the auroral ionosphere designed to check possible scenario of the initial phase of substorm are presented and discussed.     

Responses to satellite remote sensing opportunities in East and Southern Africa

Since 1978 the U.S. Agency for International Development (USAID) has funded a regional remote sensing project for East and Southern Africa. The project, hosted by the Regional Centre for Services in Surveying Mapping and Remote Sensing, has provided a programme of training courses, user services and project support. This included the equipping and establishment of a photo-laboratory complex for processing Landsat images and the provision of advice and support for agencies undertaking natural resources analysis.Response to the training programme has been very good. Courses are usually over subscribed and there is a continued demand for training. Assessments of the courses by participants are highly positive and the courses have featured consultants of international calibre. Requests for follow-up courses, and for specialist group training indicate a strong response to this training activity. User services are active, consultations with staff, use of the browse file and interpretation equipment and the purchase of data for project work all produce an average demand of 12 active enquiries per working week. The photo-laboratory is particularly active and demand for products exceeds available capacity.Project work is now being supported but limited resources restrict the range and amount of project activity. Response to the opportunities offered for projects has been favourable and this activity is ripe for expansion. The difficulty in expanding to meet the expressed demand is primarily financial. The east and southern Africa region is not economically strong and has a great need for natural resources data for development work and planning. The responses to satellite remote sensing opportunities will be limited by these financial constraints which effectively means by the level of international aid directed to this activity. For such aid to be effective it must be coordinated and firmly attached to the region. Such coordinated aid programmes would avoid fragmentation of distribution and applications work. Fragmentation could seriously disrupt the present growth in natural resources activity based on remote sensing data from satellites. The lack of financing for a regional ground receiving station is also a significant limiting factor.     

Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity.

Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.     

Immediate and long-term prospects for helioseismology

Recent extensive measurements of frequencies of free oscillation of the Sun have permitted a first direct estimate of the variation of sound speed and angular velocity throughout the Sun. The results hint that the answers to some tantalizing questions concerning the Sun's interior structure and its history are almost within grasp. Optimists like myself believe that in a few years a worldwide network of ground-based observing stations will give us important clues. However, it may be necessary to make observations from space before we can be sure of the answers.