Network to cell contrast at microwaves

Using different models deduced from EUV lines for the cell and for various network components, the corresponding radio brightness temperature in the millimetric and centimetric range of wavelengths are computed. The contrast C = [T _b (network)]/[T _b (cell)] and the difference ΔT = T _b (network) - T _b (cell) are compared with the few available observations of the quiet Sun inhomogeneities performed with sufficient angular resolution. The comparison shows a satisfactory agreement with most of the observations.     

A slowly moving plasmoid associated with a filament eruption

We report the imaging observations of a slowly moving type IV burst associated with a filament eruption. This event was preceded by weak type III burst activity and was accompanied by a quasi-stationary continuum that persisted for several hours. The starting times and speeds of moving type IV burst and the erupting filament are nearly the same, implying a close physical relation between the two. The moving type IV burst is interpreted as gyrosynchrotron emission from a plasmoid containing a magnetic field of 1–2 G and nonthermal electrons of density 10⁵–10⁶ cm^–3 with a relatively low average energy of 50 keV.     

Determination of the decameter wavelength spectrum of the quiet Sun

The Teepee Tee array of the Clark Lake Radio Observatory has been used to compare the flux of the Sun with that of the sidereal sources Tau A and Vir A at several frequencies in the range 109.0–19.0 MHz. Only the two central banks of the E-W arm of the array were used as elements of a phase switched interferometer so that the Sun could be observed as a point source and compared directly to the sidereal sources. The Sun was still partially resolved however, and appropriate corrections for this effect were made. The observations were taken at times when the Sun and either Tau A or Vir A were at the same declination. We have therefore been able to derive the values for the solar flux, without having to resort to a gain vs zenith distance correction. The observations, combined with those available in the literature, allow us to derive an accurate meter and decameter wavelength spectrum of the quiet Sun.On leave of absence from Instituto Argentino de Radioastronomía, Argentina.     

Decameter studies of the 5 September 1973 flare

We discuss the spectra and positions of the meter-decameter wavelength radio sources associated with the 5 September 1973 flare. We discuss the evolution of the size of the type II burst source and show that it fluctuates by a factor of 10, or larger. Consequently, the potential and kinetic energies associated with the shock are uncertain by the same factor. By comparing the positions of the type II and type III sources we conclude that while the shock wave associated with the type II was guided along high loops, the type III electrons were injected along open field lines which diverged within a short height in the corona. The characteristics of a particularly interesting type III burst with a low-frequency cut-off are discussed. We argue that nearby loops were not disrupted by the shock and that the energetic electrons produced during the event must have been injected at several sites and guided along open field lines at large distances from the flare to produce type III bursts.     

Microbursts at meter-decameter wavelengths

We study the characteristics of microbursts using a large data base obtained with the multifrequency radioheliograph of the Clark Lake Radio Observatory. Most of the new observations were made during July 29, 1985 to August 2, 1985; we also include for statistical studies the microburst data used in our earlier studies. We perform a statistical analysis of many characteristics such as frequency drift, source size and brightness temperature and compare them with the properties of normal type III bursts. We investigate the coronal structures and surface activities associated with some of the events. We find that (i) the brightness temperature is in the range 6 × 10⁵ K to 6 × 10⁷ K; (ii) the drift rate of the microbursts is slightly smaller than that of normal type III bursts, implying electron beams with speeds 0.2c.We explore various theoretical interpretations of the observed low brightness temperatures. We show that the microbursts can be explained as due to spontaneously emitted Langmuir waves by electron beams whereas normal type III bursts are due to coherently emitted plasma waves in a two-stream instability. We estimate the range of number densities for electron beams responsible for microbursts.On leave from Indian Institute of Astrophysics, Bangalore, India.     

An atmospheric instability derived with MODIS profile using real-time direct broadcast data over the Indian region

In this study, assessing the atmospheric instability, a new index, named here as MODIS (Moderate Resolution Imaging Spectroradiometer) profile index (MPI), has been statistically computed using temperature and moisture profile data from the real-time direct broadcast receiving systems installed at three places of India Meteorological Department. The training dataset has been prepared using MODIS temperature and moisture profile from the Aqua and Terra satellites over the Indian region for clear and convective weather conditions during the period of March to June 2011. The MPI values are produced at 5?×?5?km pixel resolution when at least 6 out of 9 FOVs from MODIS granules are found cloud free. If more than 3 FOVs are cloudy, the MPI has not been computed. The formulation of MPI and its comparison have been examined with well-established traditionally used K index, Lifted Index and total totals index derived from radiosonde profiles of temperature, pressure and humidity. It has been observed that in most of the cases, MPI has well correlated with those derived from ground truth observations. Therefore, spatially interpolated MPI can be utilized as an indicator for regional and location-specific forecast over the areas where radiosonde data are not available. The results also indicated that MPI can be used as a sensitive measure in very early stages of instability developments such as thunderstorm and rainfall because no other single stability index can provide a distinct threshold value for these events. Therefore, a single MPI value at a certain threshold can be treated as a stability index instead of other available indices. It is also being proposed that the inclusion of MPI as a stability parameter in physical or numerical modeling can improve accurate local severe storm predictions as a useful predictor and can also be used as diagnostic tools. The MPI can make a useful simulation using entire temperature and moisture profile data for the assessment of instability significantly to severe weather forecasting since other instability indices are often derived from a fixed pressure level quantity of vertical profile parameters.     

Toxicity of Diluted Dyeing and Printing Industry Effluent to a Penaeid Prawn,Parapenaeopsis sculptilis (Heller)

Experiments were carried out on the toxicity of diluted dyeing and printing industry effluent to a penaeid prawn, Parapenaeopsis sculptilis (Heller). Effluent tolerance experiments showed that both juvenile and adult prawns were unable to withstand the increasing concentration of the effluent. Juveniles were more susceptible to effluent than adults. As a consequence of higher consumption of energy due to the disturbed metabolism a decrease in the metabolite content was observed, whereas the content of ions showed an irregular trend with all the concentrations. The behavioural study showed that before death both juvenile and adult prawns became inactive, followed by paralysis. The physico-chemical nature of the effluent showed high amounts of solids, BOD, COD, sodium, magnesium, calcium, chloride, ammonium nitrogen, sulphate and absence of DO, probably causing an osmotic imbalance in the prawn body which leads to early mortality. Even a 1% concentration of such an effluent of a physico-chemical nature was reported to be toxic to the prawns.     

Simultaneous microwave observations of solar flares at 6 and 20 cm wavelengths using the VLA

Using the Very Large Array, solar burst observations have been carried out simultaneously at 6 and 20 cm. Structural changes and preheating have been observed in the flaring regions on time scales of minutes to tens of minutes before the onset of the burst impulsive phase. The 6 cm burst sources are located close to the neutral line, or near the legs of a flaring loop. The 20 cm burst sources show complex and extended structures spatially separated from both the preburst emission and the gradual decay phase of the burst. We interpret the observations in terms of a two-component flare model (bulk heating as well as acceleration of particles) and derive the physical parameters of the burst sources.On leave of absence from Indian Institute of Astrophysics, Bangalore, India.     

Role of remote sensing in residential site selection: A case study of Hisar town and its environs

To tackle the problems arising due to rapid urbanization, the urban planners need relevant data base. Since the conventional methods of data acquisition and processing ate not cost and time effective, introduction of new techniques is necessary. Application of satellite remote sensing is an alternative. Ia this paper attempt has been made to find out the usefulness of visual interpretation technique of satellite remote sensing data in the selection of new residential site. SPOT 1 HRV 1 MLA (FCC) date has been used to map existing landuse/landcover of Hisar town and its environs. Based on existing landuse/lsndcover conditions and evaluation of various suitability parameters like physiography, slope, drainage, availability of drinking water and wind direction, a new residential site has been selected. This study may be useful to the urban planners in the preparation of a comprehensive plan Df the town.     

Mapping and management of flood-affected areas through remote sensing a case study of Sirsa district,Haryana

The flood-affected areas in Siras district, Haryana, was mapped during 1993 using IRS-1A LISS-II data. Two categories of flood-affected areas viz. (i) standing water, and (ii) wet areas were identified. The flood water was standing in an area of 19676.25 ha, while wet areas covered 16773.75 ha., Silting of Ottu reservoir, mismanagement of river banks and bunds and lack of drainage system were identified, as major causes of floods. Three management practices including (i) desilting of Ottu reservoir, (ii) proper management of river banks and bands, and (iii) constructions of drains to flush out flood water have been suggested to contain the fury of floods. This study will be useful to the planners and administrators in the planning of flood-affected areas.