006628   Abdu M A (National Institute for Space Research-INPE, Sao Jose dos Campos, SP, Brazil, Email: maabdu@dae.inpe.br ) : Equatorial spread F development and quiet time variability under solar minimum conditions. Indian J Radio Space Phys 2012, 41(2), 168-83.

This paper provides a brief review of our current understanding of the equatorial spread F irregularity (ESF) development related to the diverse processes that control or influence the spatial-temporal distribution and day-to-day variability in the occurrence of the irregularities during solar minimum conditions. The sunset electrodynamics processes leading to the ESF development are briefly explained highlighting the main ESF driving forces and their relative importance during solar maximum and minimum conditions. Whereas, its post sunset occurrence characterizes the quiet time solar maximum conditions, the ESF occurrence dominates the midnight-post midnight/pre sunrise hours under solar minimum conditions. The role of the evening pre-reversal enhancement in vertical drift (PRE) relative to that of a gravity wave precursor seed, for instability growth in the ESF development, is discussed. Their relative roles vary with the level of solar activity, such that the ESF occurrence pattern tends to have larger dependence on gravity wave distribution during solar minimum conditions (than during solar maximum), which points to the importance of pursuing studies using the immense data base accumulated during the prolonged solar minimum phase that just passed. While the solar minimum spread F irregularities driven by the equatorial electrodynamics processes might be connected to the gravity waves originating from tropical convective sources, the post midnight spread F of the low-latitude region appears to be ruled mainly by the medium-scale travelling ionospheric disturbance (MSTID) of mid-latitude origin.

9 illus, 64 ref

004450   Vyas B M;Dayanandan B (Physics Dep, M L Sukhadia University, Udaipur-313 001, Email: bmvyas@yahoo.com) : Nighttime VHF ionospheric scintillation characteristics near the crest of Appleton anomaly station, Udaipur (24.6°N, 73.7°E). Indian J Radio Space Phys 2011, 40(4), 191-202.

Presents variation of percentage occurrences of nighttime VHF ionospheric scintillation characteristics in amplitude of radio beacon signals of 244/250 MHz transmitted from Fleet Satellite (positioned at 73°E longitude) received over Udaipur (24.6°N, 73.7°E, dip angle 35°) during different levels of solar activity from March 1986 to April 2000. These long time observations of VHF scintillations phenomenon, spanning a solar cycle (1986 to 2000), which covers low, mid as well as high solar activity period, have shown nighttime temporal hourly, seasonal and solar cycle variations in scintillations occurrences. The percentage occurrences of nighttime VHF radio wave scintillations have been observed with maximum percentage occurrences mostly during the equinoxes months, less during winter and the least during summer months in different phases of solar cycle. The average monthly variations of percentage occurrences of VHF ionospheric scintillations activities have been seen to be enhanced during high solar activity year and reduced during low solar activity year. The peculiar feature of discrete or patchy nature of nighttime VHF amplitude scintillations, specifically over Appleton anomaly region, has also been discussed in the light of seasonal and solar activity dependence of scintillations occurrences and their patch duration. The present observations have been compared with the earlier results reported by researchers at Indian stations specifically over similar Appleton anomaly zone and almost similar behaviour of ionospheric scintillations occurrence has been found. An attempt has been made to interpret the present findings on the basis of similarities observed between seasonal solar activity dependence of scintillations events in the present work with the earlier reported statistical observations of seasonal solar activity dependence of maximum electron density of F- region (NmF2), occurrence, and duration of range and frequency type of ESF. Furthermore, the present finding of ionospheric scintillations events have also been linked with the coincidence of numerous precursors of equatorial ionospheric parameters like rising of F-region height due to abrupt increase of upward vertical drift resulting in enhancement in eastward electric field as well as eastward drift after the sunset time over equator with experimentally observed by other researchers. The combined effect of equatorial low ionospheric irregularities phenomena such as development of equatorial ionization anomaly strength over off side of equatorial region is also discussed in view of active precursors to produce the scintillations occurrence in patchy nature away from the equatorial side from the reported studies.

3 illus, 1 table, 49 ref

004449   Roy B;Shukla A K;Sivaraman M R (SATCOM and Navigation Application Area, Space Application Centre, ISRO, Ahmedabad-380 015, Email: bijoy@sac.isro.gov.in) : Micro scale site diversity over a tropical site in India and evaluation of diversity gain with synthetic storm technique. Indian J Radio Space Phys 2011, 40(4), 211-17.

Experiment has been conducted to evaluate micro scale site diversity (MSD) at Ahmedabad, a tropical site in India. Rain data is collected by a linear array of tipping bucket rain gauges during 2007 and 2008 monsoon periods. Spatial variation of rain fall has been studied with the help of joint probability and correlation coefficients derived for the collected data. The results support the existence of micro rain cells (MRC), which are the closed contours of continuous rain with dimensions of few hundred meters. Large attenuation of signals (above 10 GHz) occursed while passing through MRCs. MSD is proposed to counteract attenuation and ensure higher link availability. An attenuation of 30 GHz signal has been estimated using synthetic storm technique (SST) in this paper and used to obtain diversity gain. The estimated diversity gain has been presented for different site separations to explore dimension of MRCs for different percentages of service availability.

6 illus, 1 table, 29 ref

004448   Jothe M K;Shrivastava P K (Physics Dep, Government MGM PG College, Itarsi-461 111, Email: jothemkj@gmail.com) : Effects of recent solar events on cosmic rays and Earth's geomagnetic field. Indian J Radio Space Phys 2011, 40(4), 179-82.

Ground based worldwide network of neutron monitors (Kiel, Oulu, Moscow and Norilsk) recorded a large decrease in cosmic ray intensity following a major solar flare that was associated with sunspot region 1092 and occurred on the Sun on 1 August 2010. A major coronal mass ejection was also recorded on 30 July 2010. The present study suggests a definite effect of this solar event (1 August 2010) on the cosmic ray intensity variation along with large interplanetary changes. As a result, a large transient decrease in cosmic ray intensity has been observed. High values of solar wind speed, total IMF B, Bz, Dst and Ap have also been observed. The results of 1 August 2010 event have been compared with the recent solar event of 15 February 2011, which is associated with Forbusch decrease (FD) in cosmic ray but not associated with coronal mass ejection (CME). The study suggests that a strong solar flare alone is capable of producing FD. However, CME associated solar flare produce more disturbances in interplanetary medium as well as geomagnetic field.

4 illus, 13 ref

004447   Das U;Sinha H S S (Space and Atmospheric Sciences Div, Physical Research Lab, Navrangpura, Ahmedabad-380 009, Email: umakota@gmail.com) : Winter equatorial mesopheric neutral turbulence. Curr Sci 2010, 99(1), 80-5.

Rohini sounding rocket carrying a Langmuir probe was flown from Thumba (8.3°N, 76.9°E), India on 27 November 2005 to study the winter equatorial mesospheric neutral turbulence from electron density measurements. The most important result of this study is the detection of a few thin intermittent turbulent layers of 100-200 m thickness, and this was possible due to the use of the continuous wavelet transform technique. This study shows that the winter turbulence is very weak. Also, the contribution of neutral turbulence process towards heating the mesosphere is significantly less during winter.

6 illus, 22 ref

003438   Adhikari U B;Parya T K (NO, Central Glass and Ceramic Research Institute, Kolkata-700 032, Email: tapanparya@yahoo.co.in) : Thermal behaviour of co-precipated magnesium-aluminium hydroxides gel. J Indian Chem Soc 2010, 87(3), 331-8.

Thermal behaviour of co-precipitated Mg-Al hydroxides gel towards the formation of composite powders of periclase and MgAl₂O₄ spinel at low temperature was investigated. The co-precipitated Mg-Al hydroxy compounds were synthesized at two different temperatures and at pH ranges in between 8.56 and 9.20 from chloride salts of respective ions with molar ratio for MgO : A1₂O₃ as 2 : 1 using various combinations of ammonium hydroxides, triethanol amine (TEA) and ammonium carbonate mixture as basic media for co-precipitation. The co-precipitated hydroxide gel dried at 110 °C and heated at different temperatures up to 1000 °C were characterised by DTA, TGA and XRD studies. In all cases the co-precipitated Mg-Al hydroxy phases collapsed at 400 °C with the conversion to transient amorphous phases. Further heat treatment at higher temperatures led to the formation of MgAl₂O₄ spinel and minor periclase phases at temperature as low as 600 °C. The co-precipitated Mg-Al hydroxides gel derived from TEA-NH₄OH basic media exhibited promising results so far as transformation to composite powders of MgAl₂O₄ spinel and periclase at relatively low temperature is concerned.

9 illus, 2 tables, 14 ref

000154   Sury B (Stat-Math Unit, Indian Statistical Institute, 8th Mile Mysore Road, Bangalore-560 059, Email: sury@isibang.ac.in) : Weierstrass's theorem- leaving no 'stone' unturned. Resonance 2011, 16(4), 341-55.

Discusses the basic theme of approximating functions by polynomial functions. Although it is exemplified by the classical theorem of Weierstrass, the theme goes much further. Even on the face of it, the advantage of polynomial approximations can be seen from the fact that unlike general continuous functions, it is possible to numerically feed polynomial interpolations of such functions into a computer and the justification that we will be as accurate as we want is provided by the theorems we discuss. In reality, this theme goes deep into subjects like Fourier series and has applications like separability of the space of continuous functions. Marshall Stone's generalisation to compact Hausdorff spaces is natural and important in mathematics. Applications of the Weierstrass approximation theorem abound in mathematics - to Gaussian quadrature for instance.

4 ref

000153   Padmanabhan T (NO, , IUCAA, Post Bag 4, Pune Campus Univ, Ganeshkhind, Pune-411 007, Email: paddy@iucaa.ernet.in ) : The copernican revolution. Resonance 2011, 16(4), 304-9.

On 24 May 1543, Nicholas Copernicus was in bed, dying of brain haemorrhage. It is said that a copy of his book De Revolutionibus Orbium Coelestium (On the Revolution of the Heavenly Bodies) - the publication of which he had delayed by nearly 30 years - was brought to his death-bed so that he could have a last glimpse of it. In this book he had detailed a system of astronomy with the Sun at the centre and the planets going around it in fixed orbits. Copernicus, so to say, stopped the Sun and set the Earth in motion.

5 illus, 2 ref

000152   Kostadinova I (NO, , <35>45, RRI Quarters, 2nd Main Road, Vyalikaval, Bangalore-560 003, Email: ivonata@gmail.com) : Two thousand metres closer to the sun-the natiobnal large solar telescope project. Curr Sci 2011, 100(8), 1148-51.

The highest and oldest functioning solar observatory in India - the Kodaikanal Solar Observatory rests on the southern tip of Palni Hills in Tamil Nadu at an altitude of 2343 m. One of the major current projects in the field of astronomy and astrophysics in India promises a new advanced 2 m solar telescope which will be located 2000 m closer to the Sun.

2 illus, 5 ref

024588   Sur U K (Chemistry Dep, Behala College, Kolkata-700 060, Email: uksur99@yahoo.co.in) : Lunar water. Curr Sci 2011, 100(5), 616-7.

2 illus, 10 ref

024587   Sharma N;Mahalakshmi D V;Gharai B;Badarinath K V S (Atmospheric Science Section, Atmospheric Sciences and Oceanography Group, National Remote Sensing Center, Hyderabad-500 013, Email: neerja_s@rediffmail.com) : GPS radio occultation observations of atmospheric heating associated with dust storm. Indian J Radio Space Phys 2011, 40(6), 320-9.

The potential ability of GPS radio occultation (GPSRO) measurements to capture the atmospheric heating during dust storm event is highlighted in the present work. COSMIC 1-dvar temperature profiles were used to study the atmospheric heating mechanism associated with the dust storm that occurred in Arabian Peninsula during 2-3 February 2008. GPSRO temperature profiles could capture the temperature inversion layer in the troposphere during the active dust storms period. Though the sensitivity of GPSRO data in the lower troposphere is limited, it could show the impact of dust storm in modulating the temperature structure of the atmosphere. The magnitude of the temperature inversion observed from the temperature profiles at different locations in different days will be helpful to understand the amount of heat trapped in the troposphere. The results are also validated with the collocated radiosonde temperature profile available with GPSRO temperature data.

14 illus, 19 ref

024586   David T W;Akintola A N;Adekoya B J (Atmospheric/Ionospheric Physics Research Group, Physics Dep, Olabisi Univ, Ago-Iwoye, Nigeria, Email: wemidavid@yahoo.com) : Time/level of ionospheric response to geomagnetic storm of 25-26 july 1981 at different latitudes. Indian J Radio Space Phys 2011, 40(6), 311-19.

The reaction of the ionosphere at different latitudes may be quite different during the same storm. In this light, this paper investigates time/level of response of the upper, mid and lower latitudes stations of two different regions to an intense geomagnetic storm. The parameters solar wind plasma and imbedded interplanetary magnetic field (IMF), and foF2 have been investigated. The data has been obtained from global network of ionosondes. The analysis of solar wind plasma show that the event on 25-26 July 1981 is a type 2 storm, i.e. the ratio of the magnitude of the second to first Dst (separated by at least 3 hours) decrease is less than 0.9. The analysis of the foF2 data shows that the depletion at the time of storm occurred at a greater percentage in the upper latitude than at the mid latitude, and very small at the lower latitudes. Furthermore, there was simultaneous depletion of foF2 at all latitudes.

3 illus, 4 tables, 20 ref

023506   Galav P;Sharma S;Pandey R (Physics Dep, Mohanlal Sukhadia Univ, Udaipur-313 001, Email: pandey.rj@gmail.com) : Total electron content in peninsular India during the eclipse of 15 january 2010. Curr Sci 2010, 99(6), 731-2.

2 illus, 10 ref

022348   Biman Nath (NO, Raman Research Institute, C V Raman Avenue, Sadashivnagar, Bangalore-50 080, Email: biman@rri.res.in ) : Sunyaev-zeldovich effect. Resonance 2011, 16(5), 428-36.

Soon after the discovery of the cosmic background radiation, Zeldovich and Sunyaev proposed that hot gas in galaxy clusters should cast a faint shadow because of the interaction between energetic electrons and the radiation photons. Sunayev-Zeldovich effect is now routinely observed, and it has become an important tool for studying the history of the universe.

5 illus, 2 ref

021176   Paul B;Naik S (NO, Raman Research Institute, Sadashivnagar, C.V. Raman Avenue, Bangalore-560 080, Email: bpul@rri.res.in) : Transient high mass X-ray binaries. Bull Astr Soc India 2011, 39(3), 429-49.

High Mass X-ray Binaries (HMXBs) are interesting objects that provide a wide range of observational probes to the nature of the two stellar components, accretion process, stellar wind and orbital parameters of the systems. A large fraction of the transient HMXBs are found to be Be/X-ray binaries in which the companion Be star with its circumstellar disk governs the outburst. These outbursts are understood to be due to the sudden enhanced mass accretion to the neutron star and is likely to be associated with changes in the circumstellar disk of the companion. In the recent years, another class of transient HMXBs have been found which have supergiant companions and show shorter bursts. X-ray, infrared and optical observations of these objects provide vital information regarding these systems. Here we review some key observational properties of the transient HMXBs and also discuss some important reªcent developments from studies of this class of sources. The X-ray properties of these objects are discussed in some detail whereas the optical and infrared properties are briefly discussed.

8 illus, 70 ref

021175   Mahabal A A et al (NO, California Institute of Technology, 1200 E California Bl., Pasadena, CA 91125, USA, Email: aam@astro.caltech.edu) : Discovery, classification, and scientific exploration of trtansient events from the catalina real-time transient survey. Bull Astr Soc India 2011, 39(3), 387-408.

Exploration of the time domain - variable and transient objects and phenomena - is rapidly becoming a vibrant research frontier, touching on essentially every field of astronomy and astrophysics, from the Solar system to cosmology. Time domain astronomy is being enabled by the advent of the new generation of synoptic sky surveys that cover large areas on the sky repeatedly, and generating massive data streams. Their scientific exploration poses many challenges, driven mainly by the need for a real-time discovery, classification, and follow-up of the interesting events. Here we describe the Catalina Real-Time Transient Survey (CRTS), that discovers and publishes transient events at optical wavelengths in real time, thus benefiting the entire community. We describe some of the scientific results to date, and then focus on the challenges of the automated classification and prioritization of transient events. CRTS represents a scientific and a technological testbed and precursor for the larger surveys in the future, including the Large Synoptic Survey Telescope (LSST) and the Square Kilometer Array (SKA).

12 illus, 1 table, 28 ref

021174   Keane E F;McLaughlin M A (Max Planck Institute fur Radioastronomie, , Auf dem Hugel 69, 53121 Bonn, Germany, Email: ekeane@mpifr-bonn.mpg.de) : Rotating radio transients. Bull Astr Soc India 2011, 39(3), 333-52.

Over the past several years, it has become apparent that some radio pulsars demonstrate significant variability in their single pulse amplitude distributions. The Rotating Radio Transients (RRATs), pulsars discovered through their single, isolated pulses, are one of the more extreme manifestations of this variability. Nearly 70 of these objects have been found over the past several years in archival and new pulsar surveys. In this review, we describe these searches and their resulting discoveries. We then discuss radio timing algorithms and the spin-down properties of the 19 RRATs with phase-connected solutions. The spin-down parameters fall within the same range as other pulsars, with a tendency towards longer periods and higher magnetic fields. Next we describe follow-up observations at radio wavelengths. These show that there are periodic fluctuations in the pulse detection rates of some RRATs and that RRATs in general have similar spectra to other pulsars. X-ray detection has only been made for one RRAT, 11819-1458; observations have revealed absorption features and a bright X-ray nebula. Finally, we look to future telescopes and the progress that will be made with these in characterising and understanding the Galactic RRAT population.

2 illus, 98 ref

021173   Kasliwal M M (Astronomy Dep, California Institute of Technology, 1200 E. California Blvd. M/C 249-17, Pasadena CA 91125, USA, Email: mansi@astro.caltech.edu) : Transients in the local universe: systematically bridging the gap between novae and supernovae. Bull Astr Soc India 2011, 39(3), 375-85.

The venerable study of cosmic explosions is over a century old. However, until recently, there has existed a glaring six-magnitude luminosity gap between the brightest novae and faintest supernovae. To find optical transients that are fainter, faster and rarer than supernovae, we designed a systematic search: the "Palomar Transient Factory". Theorists predict a variety of mechanisms to produce transients in the gap and observers have the best chance of finding them in the local Universe. Here I present discoveries and unique physics of cosmic explosions that bridge this gap between novae and supernovae.

4 illus, 1 table, 48 ref

021172   Fender R P;Bell M E (School of Physics & Astronomy, University of Southampton, Southampton, U K, Email: r.fender@ston.ac.uk) : Radio transients: an antediluvian review. Bull Astr Soc India 2011, 39(3), 315-32.

A new golden age for radio astronomy, with a new generation of facilities under construction and the global community focused on the Square Kilometre Array as its goal for the next decade. These new facilities offer orªders of magnitude improvements in survey speed compared to existing radio telescopes and arrays. Furthermore, the study of transient and variable radio sources, and what they can tell us about the extremes of astrophysics as well as the state of the diffuse intervening media, have been embraced as key science projects for these new facilities. In this paper we review the studies of the populations of radio transients made to date, largely based upon archival surveys. Many of these radio transients and variables have been found in the image plane, and their astrophysical origin remains unclear. We take this population and combine it with sensitivity estimates for the next generation arrays to demonstrate that in the coming decade we may find ourselves detecting 105 image plane radio transients per year, providing a vast and rich field of research and an almost limitless set of targets for multi-wavelength follow up.

6 illus, 1 table, 80 ref

021171   Fard H S P;Baharvandi H (Materials and Manufacturing Process Dep, Malek Ashtar Technology Univ, Tehran 15875-1744, Iran, Email: hamed.sinaie@gmail.com) : Preparation of titanium diboride powders from titanium alkoxide and boron carbide powder. Bull Mater Sci 2011, 34(4), 883-6.

Titanium diboride powders were prepared through a sol-gel and boron carbide reduction route by using TTIP and B₄C as titanium and boron sources. The influence of TTIP concentration, reaction temperature and molar ratio of precursors on the synthesis of titanium diboride was investigated. Three different concentrations of TTIP solution, 0.033/0.05/0-1, were prepared and the molar ratio of B₄C to TTIP varied from 1.3 to 2.5. The results indicated that as the TTIP concentration had an important role in gel formation, the reaction temperature and B₂C to TTIP molar ratio showed obvious effects on the formation of TiB₂. Pure TiB₂ was prepared using molar composition of Ti: B₄C = 1 : 2-3 and the optimum synthesis temperature was 1200°C.

8 illus, 13 ref

021170   Chandra P;Frail D A (Physics Dep, Royal Military College of Canada, Kingston, ON K7M3C9, Canada, Email: Poonam.Chandra@rmc.ca) : Gamma ray bursts and their afterglow properties. Bull Astr Soc India 2011, 39(3), 451-70.

Authors review the afterglow properties of 304 Gamma Ray Bursts observed WI h various radio telescopes between the year 1997 to January 20 II. Most of the observations in the sample presented here were performed in the 8.5 GHz band with the Very Large Array. Our sample shows that the detection rate for the radio afterglows has stayed at about 31 % for the pre-Swift as well as the post-Swift bursts, in contrast to large increases in the optical and X-ray afterglow detection rates. Our detailed analysis of the detected versus the non-detected radio afterglows shows that these are severely limited by the instrument sensitivity. We also find that there is no obvious correlation between the radio luminosity with the isotropic y-ray energy release, the γ-ray fluence, or with the X-ray flux; however, the optical afterglows fluxes show a weak correlation with the radio flux density. Radio afterglow detection is dependent upon a relatively narrow range of circumburst densities (1-10 cm^-3) and microscopic shock parameters, especially the magnetic energy density. Finally we discuss the most interesting bursts and some of the interesting current topics in the GRB field.

7 illus, 1 table, 92 ref

021169   Bhat P N;Guiriec S (NO, University of Alabama in Huntsville, 320 Sparkman Dr., Huntsville, Al, 35805, USA) : Overview of the current understanding of gamma ray bursts in the fermi era. Bull Astr Soc India 2011, 39(3), 471-515.

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin as well as mechanism are the focus of intense research and debate. More than three decades since their serendipitous discovery, followed by several break-throughs from space-borne and ground-based observations, they remain one of the most interesting astrophysical phenomena yet to be completely understood. Since the launch of Fermi with its unprecedented energy band width spanning seven decades, the study of gamma-ray burst research has entered a new phase. Here we review the current theoretical understanding and observational highlights of gamma-ray burst astronomy and point out some of the potential promises of multi-wavelength observations in view of the upcoming ground based observational facilities.

18 illus, 3 tables, 170 ref

021168   Bhat N D R (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Voctproa 3122, Australia, Email: rbhat@astro.swin.ed.au) : Searches for radio transients. Bull Astr Soc India 2011, 39(3), 353-73.

Exploration of the transient Universe is an exciting and fast-emerging area within radio astronomy. Known transient phenomena range in time scales from subnanoseconds to years or longer, thus spanning a huge range in time domain and hinting a rich diversity in their underlying physical processes. Transient phenomena are likely locations of explosive or dynamic events and they offer tremendous potential to uncover new physics and astrophysics. A number of upcoming next-generation radio facilities and recent advances in computing and instrumentation have provided a much needed impetus for this field .which has remained a relatively uncharted territory for the past several decades. In this paper authors focus mainly on the class of phenomena that occur on very short time scales (i.e. fiom <126> milliseconds to <126> nanoseconds), known as fast transients, the detections of which involve considerable signal processing and data management challenges, given the high time and frequency resolutions required in their explorations, the role of propagation effects to be considered and a multitude of deleterious effects due to radio frequency interference. We will describe the techniques, strategies and challenges involved in their detections and review the world-wide efforts currently under way, both through scientific discoveries enabled by the ongoing large-scale surveys at Parkes and Arecibo, as well as technical deªvelopments involving the exploratory use of multi-element array instruments such as VLBA and GMRT. Such developments will undoubtedly provide valuable inputs as next-generation arrays such as LOFAR and ASKAP are designed and commissioned. With their wider fields of view and higher sensitivities, these instruments, and eventually the SKA, hold great potential to revolutionise this relatively nascent field, thereby opening up exciting new science avenues in astrophysics.

5 illus, 1 table, 50 ref

021167   Belloni T M;Motta S E;Munoz-Darias T (NO, INAF-OSServatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Italy, Email: tomaso.belloni@brera.inaf.it) : Black hole transients. Bull Astr Soc India 2011, 39(3), 409-28.

Sixteen years of observations of black hole transients with the Rossi X-ray Timing Explorer, complemented by other X-ray observatories and ground-based optical/infrared/radio telescopes have given us a clear view of the complex phenomenology associated with their bright outbursts. This has led to the definition of a small number of spectral/timing states which are separated by marked transitions in observables. The association of these states and their transitions to changes in the radio emission from relativistic radio jets completes the picture and have led to the study of the connecªtion between accretion and ejection. A good number of fundamental questions are still unanswered, but the existing picture provides a good framework on which to base theoretical studies. We discuss the current observational standpoint, with emphasis onto the spectral and timing evolution during outbursts, as well as the prospects for future missions such as ASTROSAT (2012) and LOFT (>2020 if selected).

6 illus, 87 ref

020001   Saad S;Nouh M (NO, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt, Email: ssmsaad@nriag.sci.eg) : B+B double-lined eclipsing binary u Her. Bull Astr Soc India 2011, 39(2), 277-87.

Using new spectroscopic data, author re-investigate the B-type eclipsing binary u Her. The method of spectrum disentangling is used to decompose the spectrum of the system to its individual spectra. Comparison of the decomposed spectra with the theoretical spectra is done to obtain the main fundamental parameters for both components. Author analyzed a total of 50 new electronic spectra obtained through 1994-2004 of the spectroscopic binary star u Her. The radial velocity variations of the binary components are analyzed. The orbital solution suggests a circular orbit with a period of2.^d051 and semi amplitude of 101±1 km s^-1. Comparison against the synthetic grid gives T_eff=19000±1000K, log g=3.5±0.25 with vsini=145±5 km s^-1 for the primary and T_eff=l 1000±250K, log g=3.5±0.25 with vsinz=105±5 km S^-1 for the secondary.

7 illus, 2 tables, 28 ref

020000   Ravi Kiron Y;Sriram K;Vivekananda Rao P (Astronomy Dep, Osmania Univ, Hyderabad-500 007, Email: rkiron@gmail.com) : Photometric parameters, distance and period-colour study of contact binary stars in the globular cluster ω centauri. Bull Astr Soc India 2011, 39(2), 247-57.

Presented passband photometric solutions of six contact binaries in the globular cluster ω Centauri using the Wilson-Devinney code. author found that four of the systems are H subtype W UMa binary systems and remaining two are W-subtype W UMa systems. Four of the systems show the O'Connell effect in their light curves and brightness at 0.75 phase is about δV=0.04-0.05 less than at 0.25 phase. Author that one dark/cool spot solution on secondary companion satisfactorily fits the observed light curves for the respective contact binaries. The derived spot values are not unique and they are taken to be tentative at best. The colour index of the six contact binaries were used to derive the distance modulus of ω Centauri and found an average value of <126> 13.60 which is close to the observed value of 13.97. Also derive the distance to each of the studied variables. The period-colour relation of the contact binaries of ω Centauri is compared with the period-colour relation of Hipparcos data (field W UMa type) and contact binaries present in other globular clusters.

41 ref

019999   Pirya A;Nandi S;Saikia D J;Singh M (NO, Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital-263 129, Email: akashpirya@gmail.com) : Low-frequency study of two asymmetric large radio galaxies. Bull Astr Soc India 2011, 39(4), 547-62.

Author presented the results of multifrequency observations of two asymmetric, Mpc-scale radio sources with the Giant Metrewave Radio Telescope (GMRT) and the Very Large Array (VLA). The radio luminosity of these two sources, J1211+743 and J1918+742, are in the Fanaroff-Riley class II (FRII) range, but have diffuse radio components on one side of the galaxy while the opposite component appears edge-brightened with a prominent hot-spot. Although the absence of a hot-spot is reminiscent of FRI radio galaxies, suggesting a hybrid morphology, the radio jet facing the diffuse lobe in J1211 +743 is similar to those in FRII radio sources, and it is important to consider these aspects as well while classifying these sources in the FR scheme. The observed asymmetries in these Mpc-scale sources are likely to be largely intrinsic rather than being due to the effects of orientation and relativistic motion. The formation of a diffuse lobe facing the radio jet in J1211+743 is possibly due to the jet being highly dissipative. The low-frequency spectral indices of the lobes are in the range of approximately -0.8 to -1, while at the outer edges these vary from approximately -0.65 to -1.05 suggesting steep injection spectral indices, which need to be examined further from observations at even lower frequencies by telescopes such as the LOw Frequency ARray (LOFAR).

5 illus, 3 tables, 65 ref

019998   Mitra S;Kulkarni G;Bagla J S;Yadav J K (NO, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad-211 019, Email: smitra@hri.res.in) : Formation rates of dark matter haloes. Bull Astr Soc India 2011, 39(4), 563-91.

Author derived an estimate of the rate of formation of dark matter haloes per unit volume as a function of the halo mass and redshift of formation. Analytical estimates of the number density of dark matter haloes are useful in modeling several cosmologi-cal phenomena. We use the excursion set formalism for computing the formation rate of dark matter haloes. We use an approach that allows us to differentiate between major and minor mergers, as this is a pertinent issue for semi-analytic models of galaxy formation. Authorcomputed formation rate for the Press-Schechter and the Sheth-Tormen mass function. Athor that the formation rate computed in this manner is positive at all scales. Comments on the Sasaki formalism where negative halo formation rates are obtained. Our estimates compare very well with N-body simulations for a variety of models. Also discussed the halo survival probability and the formation redshift distributions using the method.

15 illus, 2 tables, 74 ref

019997   Mathew B;Subramaniam A (Astronomy and Astrophysics Division, Physical Research Laboratory, Navrangapura, Ahmedabad-380 009) : Optical spectroscopy of classical Be stars in open clusters. Bull Astr Soc India 2011, 39(4), 517-37.

Author presented a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800 - 9000 A. One-third of the sample (48 stars in 18 clusters) has been studied for the first time. All these candidates were identified from an extensive survey of emission stars in young open clusters using slitless spectroscopy (Mathew et al. 2008). This large data set covers CBe stars of various spectral types and ages found in different cluster environments in largely northern open clusters, and is used to study the spectral characteristics of CBe stars in cluster environments. About 80% of CBe stars in our sample have Hα equivalent width in the range -1 40 Angstrum. About 86% of the surveyed CBe stars show Fell lines. The prominent Fell lines in our surveyed stars are 4584, 5018, 5169, 5316, 6318, 6384, 7513 and 7712 Angstrum. Identified short- and long-term line profile variability in some candidate stars through repeated observations.

5 illus, 3 tables, 15 ref

019996   Green D A (NO, Cavendish Laboratory, 19 J.J. Thomson Avenue, Cambridge CB3 0HE, U.K., Email: dag@mrao.cam.ac.uk) : Colour scheme for the display of astronomical intensity images. Bull Astr Soc India 2011, 39(2), 289-95.

Described a colour scheme that is appropriate for the screen display of intensity images. This - unlike many currently available schemes - is designed to be monotonically increasing in terms of its perceived brightness. Also, when printed on a black and white postscript printer, the scheme results in a greyscale with monotonically increasing brightness. This scheme has recently been incorporated into the radio astronomical analysis packages CASA and AIPS.

1 illus, 7 ref

019995   George S J;Stevens I R (Astrophysics Group, The Cavendish Laboratory, JJ Thomson Avenue, Cambridge Univ, Cambridge, CB3 OHE, UK, Email: sgeorge@mrao.cm.ac.uk) : Optical observations of ultra steep spectrum radio sources. Bull Astr Soc India 2011, 39(4), 539-45.

Presents follow-up optical observations of Ultra Steep Spectrum sources that were found by matching 150 MHz GMRT sources with either the 74 MHz VLSS or the 1400 MHz NVSS. These sources are possibly high-redshift radio galaxies but optical identification is required for clarification. The follow-up observations were conducted with the Liverpool Telescope; in all cases no sources are detected down to an R magnitude of <126>23. By applying models and using the K - z relation we are able to suggest that these sources are possibly at high redshift. Author discussed how 2m class telescopes can help with the identification of HzRGs from large-scale, low-frequency surveys.

1 illus, 3 tables, 17 ref

018943   Bhattacharya A B;Tripathi D K;Sarkar A; Bhoumick A (Physics Dep, University of Kalyani, Kalyani-741 235, Email: asit1951@yahoo.com) : Implementation of radio technique in interstellar radiation field for locating distant stars. Int J appl Engng Res Dindigul 2011, 2(1), 63-9.

Alternative search strategy implementing the method of radio technique may be considered appropriate for locating distant stars in presence of the interstellar radiation field. For the purpose we have taken into account the available data of known stars/constellations up to the recent years to find the required time of reception of the echo radio signals, if transmitted using the wavelengths corresponding to the "water holes" from the earth's station. It further investigates the probable responding number of stars due to different transmitted power.

5 illus, 1 table, 19 ref

017752   Raut J V;Vhatkar R S (Physics Dep, Government Polytechnic, Miraj-416 410, Email: drhatkar@gmail.com) : Long-term atmospheric effects of very large solar proton event in July 2000 over Sodankyla, Finland. Asian J chem envir Res 2011, 4(3-4), 99-104.

The third largest solar proton event (SPE) in past 40 years took place during July 14-16, 2000 and had a significant impact on stratospheric and mesospheric composition. The highly energetic protons associated with this SPEs cause ionization, dissociation and dissociative ionization of background constituents. Complicated ion chemistry of D region (60-95km) led to HOx production and dissociation of N₂ led to long- lived NOy production. Both HOx and NOy play a key role in control of ozone abundance through well- known ozone destroying catalytic cycles. Temporal enhancement in NO₂ and decrease in O₃ during this event over Sodankyla (67.4° N, 26.7° E), Finland is measured by Global Ozone Monitoring Experiment (GOME) aboard on European Remote Sensing (ERS-2) satellite. Station Sodankyla is selected only because of its vicinity to polar region. Maximum NO₂ abundance is observed in first ten days after event, when maximum SPE took place. Measurement from GOME instrument indicates long - term middle stratospheric ozone decrease of over 9-11% caused by long- lived NO₂ species.

4 illus, 3 tables, 7 ref

012091   Pal P C;Sen B (Applied Mathematics Dep, Indian School of Mines, Dhanbad, Jharkhand, Pin-826004, Email: pcpal_ism@yahoo.co.in) : Reflection and refraction of plane waves in randomly stratified media. Int J theor appl mech 2010, 5(1), 63-71.

In this paper the propagation of the plane waves in a two dimensional randomly stratified transversely isotropic elastic medium are considered. Two cases viz. one for longitudinal and another for transversely plane waves are considered. The reflection and refraction coefficient are obtained. The numerical results are shown graphically for various values of angle of inclinations.

4 illus, 21 ref

012090   Ajith P;Arun K G (NO, Ajith LIGO Laboratory and Theoretical Astrophysics California Institut, MS 18-34, Pasadena CA 91125, USA, Email: ajith@caltech.edu) : Gravitational-wave astronomy. Resonance 2011, 16(10), 922-32.

Presents a broad overview of the emerging field of gravitational-wave astronomy. Although gravitational waves have not been directly detected yet, the worldwide scientific community is engaged in an exciting search for these elusive waves. Once detected, they will open up a new observational window to the Universe.

3 illus, 8 ref

010968   Whitney B A (Astronomy Dep, University of Wisconsin-Madison, 475 N, Charter St., Madison, WI 53706, USA, Email: bwhitney@astro.wisc.edu) : Monte Carlo radiative transfer. Bull Astr Soc India 2011, 39(1), 101-27.

I outline methods for calculating the solution of Monte Carlo Radiative Transfer (MCRT) in scattering, absorption and emission processes of dust and gas, including polarization. I provide a bibliography of relevant papers on methods with astrophysical applications.

1 illus, 147 ref

010967   Van Den Heuvel E P J (Univ of Amsterdam, Astronomical Institute, "Anton Pannekoek", The Netherlands) : Compact stars and the evolution of binary systems. Bull Astr Soc India 2011, 39(1), 1-20.

The Chandrasekhar limit is of key importance for the evolution dwarfs in binary systems and for the formation of neutron stars and black holes in binaries. Mass transfer can drive a white dwarf in a binary over the Chandrasekhar which may lead to a Type la supernova (in case of a CO white dwarf) or an Accretion- Induced Collapse (AIC, in the case of an O-Ne-Mg white dwarf; and possibly some CO white dwarfs) which produces a neutron star. The direct formation of neutron stars or black holes out of degenerate stellar cores that exceed the Chandrasekhar limit, occurs in binaries with components that started out with masses ≥ 8 M. This paper first discusses possible models for Type la supernovae, focusses on the formation of neutron stars in binary systems, by direct core and by the AIC of O-Ne-Mg white dwarfs in binaries. Observational evidence viewed for the existence of two different direct neutron-star formation me, in binaries: (1) by electron-capture collapse of the degenerate O-Ne-Mg core with initial masses in the range of 8 to about 12 M, and (ii) by iron-core in stars with initial masses above this range. Observations of neutron stars in binaries are consistent with a picture in which neutron stars produced bye-capture have relatively low masses, <126>1.25 M, and received hardly any velocity kid whereas neutron stars produced by iron-core collapses are more massive and large velocity kicks at birth. Many of the globular cluster neutron stars and a of the neutron stars in low-mass binaries in the Galactic disk are likely to h produced by AIC of O-Ne-Mg white dwarfs in binaries. AIC is expected to normal strongly magnetized neutron stars, which in binaries can evolve into millisecond pulsars through the usual recycling scenario.

3 illus, 1 tables, 86 ref

010966   Stone J M (Astrophysical Sciences Dep, Princeton University, Princeton, NJ 08540 USA, Email: jmstone@princeton.edu) : Astrophysical magnetohydrodynamics. Bull Astr Soc India 2011, 39(1), 129-43.

Over the course of roughly a decade, from the late 1950s through the early 1960s, Chandraskhar made fundamental contributions to basic plasma physics, and the effect of magnetic fields on the dynamics of astrophysical plasmas. This paper reviews recent progress and outstanding problems in Astrophysical magnetohydrodynamics, the application of MHD to astrophysical systems, with particular emphasis on the role of Chandra's early contributions to the field. Specific topics discussed include magnetic field amplification by dynamo processes inside stars, the magnetorotational instability and angular momentum transport in accretion disks, MHD turbulence in the interstellar medium of galaxies, and kinetic MHD effects in weakly collisional plasmas. Chandra's contributions in all of these areas endure.

5 illus, 31 ref

010965   Souradeep T (NO, IUCAA, Post Bag 4, Ganeshkhind, Pune, Email: tarun@iucaa.ernet.in) : Early Univese with CMB polarization. Bull Astr Soc India 2011, 39(1), 163-80.

The Universe is the grandest conceivable scale on which the human mind can strive to understand nature. The amazing aspect of cosmology, the branch of science that attempts to understand the origin and evolution of the Universe, is that it is largely comprehensible by applying the same basic laws of physics that we use for other branches of physics. The observed cosmic microwave background (CMB) is understood by applying the basic laws of radiative processes and transfer, masterfully covered in the classic text by S. Chandrasekhar, in the cosmological context. In addition to the now widely acclaimed temperature anisotropy, there is also linear polarization information imprinted on the observed Cosmic Microwave background. CMB polarization already has addressed, and promises to do a lot more to unravel the deepest fundamental queries about physics operating close to the origin of the Universe.

6 illus, 51 ref

010964   Natarajan P (Astronomy Dep, Yale University, 260 Whitney Avenue, New Haven CT 06511, Email: priyamavada.natarajan@yale.edu) : Formation and evolution of massive black hole seeds in the early Universe. Bull Astr Soc India 2011, 39(1), 145-61.

Tracking the evolution of high redshift seed black hole masses to late times, author examine the observable signatures today. These massive initial black hole seeds form at extremely high redshifts from the direct collapse of pre-galactic gas discs. Populating dark matter halos with seeds formed in this fashion, Author follow the mass assembly history of these black holes to the present time using a Monte-Carlo merger tree approach. Utilizing this formalism, they predict the black hole mass function at high redshifts and at the present time; the integrated mass density of black holes in the Universe; the luminosity function of accreting black holes as a function of red shift and the scatter in observed, local M_bh - σ relation. Comparing the predictions of the 'light' seed model with these massive seeds we find that significant differences appear predominantly at the low mass end of the present day black hole mass function. How-ever, all our models predict that low surface brightness, bulge-less galaxies with large discs are least likely to be sites for the formation of massive seed black holes at high redshifts. The efficiency of seed formation at high redshifts has a direct influence on the black hole occupation fraction in galaxies at z = O. This effect is more pronounced for low mass galaxies. This is the key discriminant between the models studied here and the Population III remnant 'light' seed model. There exists a population of low mass galaxies that do not host nuclear black holes. Prediction of the shape of the M_bh - σ relation at the low mass end and increased scatter has recently been corroborated by observations.

6 illus, 67 ref

010963   Joshi P S (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400005, India, Email: psj@tifr.res.in) : Key problems in black hole physics today. Bull Astr Soc India 2011, 39(1), 49-68.

Objective is to review here some of the major open issues and challenges in black hole physics today, and the current progress on the same. It is pointed out that to secure a concrete foundation for the basic theory as well as astrophysical applications for black hole physics, it is essential to gain a suitable insight into these questions. In particular, we discuss the recent results investigating the final fate of a massive star within the framework of the Einstein gravity, and the stability and genericity aspects of the gravitational collapse outcomes in terms of black holes and naked singularities. Recent developments such as spinning up a black hole by throwing matter into it, and physical effects near naked singularities are considered. It is pointed out that some of the new results obtained in recent years in the theory of gravitational collapse imply interesting possibilities and understanding for the theoretical advances in gravity as well as towards new astrophysical applications.

6 illus, 39 ref

010962   Heggie D C (University of Edinburgh, School of Mathematics and the Maxwell Institute for Mathematical Scien, King's Buildings, Edinburgh EH9 3JZ U.K., Email: d.c.heggie@ed.ac.uk) : Problems of collisional stellar dynamics. Bull Astr Soc India 2011, 39(1), 69-85.

The discovery of dynamical friction was Chandrasekhar's best known contribution to the theory of stellar dynamics, but his' work ranged from the few-body problem to the limit of large N (in effect, galaxies), Much of this work was summarized in the text "Principles of Stellar Dynamics" (Chandrasekhar 1942,1960), which ranges from a precise calculation of the time of relaxation, through a long analysis of galaxy models, to the behaviour of star clusters in tidal fields, The later edition also includes the work on dynamical friction and related issues, In this review author focus on progress in the collisional aspects of these problems, i.e, those where few-body interactions Play a dominant role, and so they omit further discussion of-galaxy dynamics,2 But W0 y to link Chandrasekhar's fundamental discoveries in collisional problems with the progress that has been made in the 50 years since the publication of the enlarged edition.

3 illus, 134 ref

010961   Garmire G P (NO, Penn State University, PA 16802, USA, Email: garmire@astro.psu.edu) : Chandra X-ray observatory. Bull Astr Soc India 2011, 39(1), 225-41.

This paper describes a brief history of the development of the Chandra X -ray observatory, based on the talk which was presented on October 17, 2010 at the Chandrasekhar Centennial Symposium held in the campus of the University of Chicago.

11 illus, 15 ref

010960   Friedman J L;Stergioulas N (Physics Dep, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA, Email: friedman@uwn.edu (JF)) : Stability of relativistic stars. Bull Astr Soc India 2011, 39(1), 21-48.

Stable relativistic stars form a two-parameter family, parametrized by mass and angular velocity. Limits on each of these quantities are associated with relativistic instabilities discovered by Chandrasekhar: A radial instability, to gravitational collapse or explosion, marks the upper and lower limits on their mass; and an instability driven by gravitational waves may set an upper limit on their spin. Our summary of relativistic stability theory given here is based on and includes excerpts from the book Rotating Relativistic Stars, by the present authors (Friedman & Sterigioulas 2).

3 illus, 132 ref

010959   Ferrari V (Dipartimento di Fisica G Marconi, Sapienza Universita di Roma and Sezione INFN ROMAI, Piazzale Aldo Moro 5, 00185 Roma, Italy, Email: valeria.ferrari@roma1.infn.it) : Gravitational waves from perturbed stars. Bull Astr Soc India 2011, 39(1), 203-24.

Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.

5 illus, 66 ref

010958   Evans N W (NO, Institute of Astronomy, Madingley Rd, Cambridge, CB3 OHA, UK, Email: nwe@ast.cam.ac.uk) : Chandrasekhar and modern stellar dynamics. Bull Astr Soc India 2011, 39(1), 87-9.

Stellar dynamics occupied Chandrasekhar's interest for a brief interlude between his more prolonged studies of stellar structure and radiative transfer. This paper traces the history of one of his ideas - namely, that the shape of the galactic potential controls the orientation of the stellar velocity dispersion tensor. It has its roots in papers by Eddington (1915) and Chandrasekhar (1939), and provoked a fascinating dispute between these two great scientists - less well-known than their famous controversy over the white dwarf stars. In modem language, Eddington claimed that the integral curves of the eigenvectors of the velocity dispersion tensor provide a one-dimensional foliation into mutually orthogonal surfaces. Chandrasekhar challenged this, and explicitly constructed a counter-example. In fact, the work of neither of these great scientists was without flaws, though further developments in stellar dynamics were to ultimately draw more on Eddington's insight than Chandrasekhar's. We conclude with a description of modem attempts to measure the orientation of the velocity dispersion tensor for populations in the Milky Way Galaxy, a subject that is coming into its own with the dawning of the age of precision astrometry.

2 illus, 47 ref

010957   Dhurandhar S V (NO, Inter University Centre for Astronomy & Astrophysics, Ganeshkhind, Pune-411007, Email: sanjeev@iucaa.ernet.in) : Gravitational wave astronomy - astronomy of the 21st century. Bull Astr Soc India 2011, 39(1), 181-202.

An enigmatic prediction of Einstein's general theory of relativity is gravitational waves. With the observed decay in the orbit of the Hulse-Taylor binary pulsar agreeing within a fraction of a percent with the theoretically computed decay from Einstein's theory, the existence of gravitational waves was firmly established. Currently there is a worldwide effort to detect gravitational waves with inteferometric gravitational wave observatories or detectors and several such detectors have been built or being built. The initial detectors have reached their design sensitivities and now the effort is on to construct advanced detectors which ~ expected to detect gravitational waves from astrophysical sources. The era of gravitational wave astronomy has arrived. This article describes the worldwide effort which includes the effort on the Indian front - the IndIGO project -, the principle underlying interferometric detectors both on ground and in space, the principal noise sources that plague such detectors, the astrophysical sources of gravitational waves that one expects to detect by these detectors and some glimpse of the data analysis methods involved in extracting the very weak gravitational wave signals from detector noise.

6 illus, 43 ref

004166   Sunil Krishna M V;Sandeep Kaur;Singh V (Physics Dep, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: suneelfph@iitr.ernet.in) : Heating of ambient electrons in thermosphere under varying solar activity conditions. Indian J Radio Space Phys 2011, 40(3), 130-6.

The suprathermal electron flux plays a very important role in the production of various airglow emissions. The solar extreme ultra violet (EUV) photons and X-rays are mainly responsible for the production of suprathermal electrons in the atmosphere. These suprathermal electrons further cause heating of ambient electrons in the thermosphere. In the present study, the heating rate of ambient electrons in the thermosphere under the effect of varying solar activity has been studied. The suprathermal electron flux has been calculated as a function of suprathermal electron energy. The fluxes have been calculated at various levels of solar activity and various geographic locations during a period of five years (2001-2005). This flux has been further used to calculate the ambient electron heating rate in the thermosphere. It has been found that the maximum electron heating rate is near 30°N latitude. It has been found that the maximum electron heating rate does not vary linearly with F10.7 solar index. The altitude of the peak heating rate does not show any appreciable variation with the solar activity at a fixed latitude. The altitude of peak electron heating rate moves upwards as the latitude increases from equator towards pole at the fixed value of F10.7 solar index.

3 illus, 32 ref

004165   Mahalakshmi D V;Badarinath K V S;Naidu C V (Atmospheric Science Section, National Remote Sensing Centre, Space Dep, Govt of India, Balanagar, Hyderabad-500 625, Email: mahameteor@yahoo.com) : Influence of boundary layer dynamics on pollutant concentrations over urban region - a study using ground baed measurements. Indian J Radio Space Phys 2011, 40(3), 147-52.

Ventilation coefficient (VC) over urban area of Hyderabad, India during night-time in 2008 has been calculated using night-time mixed layer height with boundary layer lidar (BLL) and radiosonde data to investigate the influence of VC on pollutant concentration. Carbon monoxide (CO), ozone (O₃) and black carbon (BC) aerosol mass concentrations in relation to mixed layer height and wind speed have been analysed for different seasons, viz. winter, pre-monsoon, monsoon and post-monsoon associated with boundary layer and ventilation coefficient (VC). The results of the study suggested that VC plays an important role in dispersing the pollutants.

6 illus, 21 ref

004164   Kane R P (NO, Institute National de Pesquisas Espaciais-INPE, CP 515 Sao Campos,12245-970 SP, Brazil, Email: kane@dge.inpe.br) : Bartel diagrams for CME occurrence frequency, sunspot numbers and 2800 MHz solar radio emission flux during 2007. Indian J Radio Space Phys 2011, 40(3), 121-3.

During 2007, the relationship of the variations in the daily values of sunspot number (Rz) and the 2800 MHz solar radio emission F-10 was good only in some intervals, while relationship of both Rz and F-10 with the coronal mass ejections (CMEs) was very poor, indicating that CMEs evolve independently of Rz and F-10.

1 illus, 1 table, 4 ref