011725   Srivastava P (NO, Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun-248 001, Email: pradeep@wihg.res.in) : River systems of Himalaya: archive of past climate and tectonics. Proc Indian Natn Sci Acad 2012, 78(3), 295-8.

River systems in Himalaya evolve interacting with climatic changes and neotectonic adjustments that take place in this mountainous region. The resulting landscape thus becomes an important archive to understand the past climato-tectonic conditions. This article reviews the published peer reviewed literature dealing with river systems draining the Himalaya and its foreland between 2007-11. The rivers in Himalaya from NW-NE preserve morphostratigraphic records suggesting their in-phase oscillation with climate. Aggradation takes place in the climatic transition from drier to wetter and the incision during the enhanced monsoon phases. Geomorphic configuration of the terraces indicate that the mountain front is deforming at higher rates but there are zones of deformation occurring within the Himalayan prism as well. The geochemical proxies indicate the increased erosion from lesser Himalaya during the weaker monsoon phases and from Higher Himalaya during the wetter phases.

36 ref

011724   Chauhan P;Prabhjot Kaur;Kiran Kumar A S (NO, Space Applications Centre, (ISRO), Ahmedabad-380 015, Email: prakash@sac.isro.gov.in) : Lunar geosciences using Chandrayaan-1: Indian perspective. Proc Indian Natn Sci Acad 2012, 78(3), 239-47.

The successful launch of Chandrayaan-1 satellite allowed Indian lunar scientists to get firsthand experience of working with higher resolution lunar data sets in unprecedented details to look into various lunar science studies. Data from different instruments on-board Chandrayaan-1 have been used to assess lunar surface morphology, mineralogy, elemental abundance and detection of water/ice in the polar regions and these results were supported with high resolution topographic data from more than one sensor. This paper attempts to provide an overall summary of various science results obtained using Chandrayaan-1 data to answer questions related to lunar science.

7 illus, 37 ref

010605   Tank H K (NO, Indian Space Research Organisation, 22/693, Krishna Dham-2, Vejalpur, Ahmedabad-380 015, Email: hasmukh.tank1@gmail.com) : Some expressions for gravity without the big G and their possible wave-theoretical explanation. Proc Indian Natn Sci Acad 2012, 78(4), 645-50.

This letter presents some new expressions for gravity without the big G and proposes their possible wave-theoretical-explanation. This attempt leads to some insight that: (i) We need the proportionality-constant G because we measure masses and distances in our arbitrarily-chosen units of Kg. and Meters; whereas nature has her own units; if we measure masses in the units of 'total-mass of the universe' M₀ and measure distances in the units of 'radius-of-the-universe' R₀ then there is no need for any proportionality-constant. However, large uncertainties in the M₀ and R₀ limit the general application of this relation presently, (ii) The strength of gravity would be different if the total-mass of the universe were different. Then this conclusion is explained with the help of wave-theory, (iii) These new expressions lead to an insight that Planck's-length, Planck-mass and Planck's unit of time are geometric-mean-values of astrophysical quantities like: total-mass of the universe and the smallest-possible-mass h H₀/ c². (iv) There is a law followed by various systems-of-matter, like: the electron, the proton, the nucleus-of-atom, the globular-clusters, the spiral-galaxies, the galactic-clusters and the whole universe; that their ratio Mass/Radius² remains constant. This law seems to be more fundamental than the fundamental-forces because it is obeyed irrespective of the case, whether the system is bound by strong-force, electric-force, or gravitational-force.

8 ref

010604   De S S;Bandyopadhyay B;Paul S;Haldar D K;Bose M;Kala D;Guha G (S K Mitra Centre for Research in Space Environment, Centre of Advanced Study in Radio Physics and Electronics, Calcutta Un, Kolkata-700 009, Email: de_syam_sundar@yahooc.o.in) : Atmospheric electric potential gradient at Kolkata during solar eclipse of 22 July 2009. Indian J Radio Space Phys 2013, 42(4), 251-8.

Measurement of atmospheric electric potential gradient (PG) at Kolkata (latitude 22.56°N, longitude 88.5°E) during solar eclipse of 22 July 2009 has been carried out. The effects of solar eclipse on the potential gradient are presented in the paper, which show significant changes in the value during the eclipse period than their ambient values for the same period on other days. It shows that the PG value decreases about 38% during the eclipse period with some irregular variation during rest of the day. The results of measurements of ground level conductivity, temperature and relative humidity are also presented and discussed on the basis of change in conductivity due to eclipse, effects of global thunderstorm centers and local effects.

6 illus, 1 table, 29 ref

006351   Lal D;Chauhan P;Shah R D;Bhattacharya S;Ajai; Kiran Kumar A S (M.G. Science Institute Gujarat Univ, Ahmedabad, Gujarat, Email: prakash@sac.isro.gov.in) : Detection of Mg spinel lithologies on central peak of crater theophilus using moon mineralogy mapper (M<. J Earth Syst Sci 2012, 121(3), 847-53.

Spectral reflectance data derived from Moon Mineralogy Mapper (M3) onboard India's Chandrayaan-1 has revealed Fe bearing Mg-spinel-rich lithology on central peaks of the crater Theophilus. These newly identified Fe bearing Mg-spinel-rich rock types are defined by their strong 2-μm absorption and lack of 1-μm absorptions in spectral reflectance response. Such lithology has been reported previously along the inner ring of Moscoviense Basin on the lunar far side. The Modified Gaussian Modeling (MGM) analysis of the Fe bearing Mg-spinel reflectance spectra has been done and the results of the analysis clearly bring out a strong spectral absorption at 1872 nm with no significant absortion around 1000 nm. The presence of spinel group of minerals in the Theophilus central peak and the fact that central peaks mostly represent uplifted mass of deep crustal material confirm that central peaks can be used as a window to study the deep crustal and/or upper mantle composition and may lead to a fresh perspective about the crustal composition of Moon.

7 illus, 1 table, 26 ref

006350   Boranayaka M B;Ibrahim S M;Rajesha G; Shadakshari T V;Ashoka K R;Raghavendra K (P.C. Unit (Small Millets), Zonal Agricultural Research Station, Agricultural Sciences Univ, G.K.V.K., Bengaluru, Karnataka, Email: mbboranayak@gmail.com) : Gamma rays and ethyl methane sulphonate induced pollen sterility in sesame (Sesamum indicum L.). Int J Pl Sci 2011, 6(2), 240-12.

Five dosages of gamma rays ranging from 10 (V₁, T₁)to 50 krad (V₁ T₅) with an interval of 10 krad and five concentrations of Ethyl methane sulphonate (EMS) ranging from 0.8 (V₂ T₁)to 1.6 per cent (V₂ T₅) with an interval of 0.2 per cent were employed to study pollen fertility in two sesame genotypes viz., SVPR 1 and Cardeboriga. Both the mutagens exhibited significant differences for pollen fertility. All the treatments in both the genotypes produced considerable pollen sterility indicating that the mutagens were capable of bringing about either large or cryptic structural differences. The pollen fertility of M₁ plants showed decreasing trend as the dosage of mutagen increased in both the genotypes.

2 illus, 1 table, 12 ref

004265   Okoh D;Esimbek J;Xindi J Zhou T;Chukwude A; Urama J;Okeke P (NO, Xinjiang Astronomical Observatory, 150 Science 1-Street, Urumqi, Xinjiang-830 011, China, Email: okodan2003@gmail.com) : Machine learning approach for investigating spatial structures between spectral line sources: formaldehyde absorptions versus methanol masers. Res Rev : J Space Sci Technol 2013, 2(2), 1-11.

In this paper the authors present fascinating ideas on using machine learning algorithms to study connections in spatial distributions between observed spectral line sources. The method has been illustrated using observations of 4.8 GHz formaldehyde absorptions and 6.7 GHz methanol masers in the Galaxy. Both spectral line features have been well-observed in close associations with galactic star-formation regions, and author initiate this study to understand spatial connections between them. Implemented the K-means unsupervised clustering algorithm after using a modification of other machine learning practices to identify optimal number of structures in the galactic distributions of the observations. Found very close associations and interwoven spatial distributions in 25 of the 28 clusters identified in the work; formaldehyde absorptions were observed in all of the methanol maser clusters, and methanol masers were observed in all (but 3) of the formaldehyde clusters, an indication that the two lines are closely related.

1 illus, 7 tables, 67 ref

004264   Bhargava S;Rajwanshi L K (Chemistry Dep, University of Rajasthan, Jaipur-302 004, Email: drsbhargaval@gmail.com) : Synthesis of some novel pyrido[2,3-d]pyrimidine derivatives and their antimicrobial investigations. Indian J Chem-Sect B 2013, 52(3), 448-52.

Series of pyrido[2,3-d]pyrimidine derivatives viz 45,7-disubstituted pyrido[2,3-d]pyrimidines 3a-d, 4disubstituted pyrido[2,3-d]pyrimidin-2(lH)-ones 4a-d and 44amino-5,7-disubstituted pyrido[2,3-d]pyrimidin-2(1H)-thione Saad have been synthesized by the condensation reaction of 23-cyano-4,6-disubstituted pyridines 2a-d with formamide, urea and thiourea, respectively. The newly synthesized compounds have been established by elemental analysis, IR, IH and I3C NMR. All the synthesized compounds have been screened for their antibacterial and antifungal activity.

^ssc1 table, 18 ref

003207   Sugathan N;Biju V;Renuka G (Physics Dep, University of Kerala, Kariavattom-695 581, Email: drgrenuka@gmail.com) : Solar activity and regional climate over short time scales at Thiruvananthapuram, South Kerala, India. Indian J Radio Space Phys 2013, 42(2), 69-72.

Possible correlation between solar activity and surface air temperature, however, small yet statistically significant that could exist over very small time scales at a particular station, is presented during a period in which the sunspot number exhibit a rising trend. The correlation between the variability of the daily and monthly average surface air temperature and solar irradiance at Trivandrum with sunspot number from January 2008 to March 2011 was investigated. The year 2008 was a solar minima year marking the end of 23rd solar cycle from May 1996 to December 2008 with duration of 12.6 years, while year 2009 was the beginning of the 24th solar cycle with the sunspot number showing a gradual rise during 2009-2010. The correlation between sunspot number, solar irradiance and surface air temperature were estimated during winter and pre-monsoon seasons when the effect of clouds was minimum. No statistically significant correlation was obtained between the surface air temperature or solar irradiance and sunspot number over small time scales unlike the small yet statistically significant correlation reported for studies over longer time scales.

3 illus, 8 ref

003206   Pandey U;Chauhan V;Singh B (Electronics and Communication Engineering Dep, Faculty of Engineering, R B S College, Bichpuri, Agra-283 105, Email: pandeyuma68@gmail.com) : Magnetospherically reflected (MR) whistlers observed in DEMETER satellite and on the ground observation of normal whistlers at low latitudes. Indian J Radio Space Phys 2013, 42(2), 97-104.

DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite data have been analysed for a period of three and half months from 01 September to 16 December 2010 in search of whistlers and VLF emissions and their ground observations at low latitudes. The quick look data show intense sporadic bursts mostly in the Instrument Champ Electrique (ICE) channel of the satellite. These bursts are analysed using MATLAB software for the nighttime passes of upgoing orbits in the latitude range 20°-50°. The analysis shows records of large number of first component of magnetospherically reflected (MR) whistlers, mostly when the satellite is in low latitude ionosphere. These whistlers, together with normal whistlers observed in the satellite, are not observed on the ground as revealed by simultaneous ground observations at low latitude station Agra. This confirms them to be non-ducted whistlers which are reflected and observed in the ionosphere and magnetosphere. These MR whistlers are suggested to be the major source of slot formation between the two radiation belts.

5 illus, 30 ref

003205   Ikubanni S O;Adebesin B O;Adebiyi S J;Adeniyi J O (Physical Sciences Dep, Landmark University, PMB 1001, Omu-Aran, Nigeria, Email: ikubanni.stephen@lmu.edu.ng) : Relationship between F2 layer critical frequency and solar activity indices during different solar epochs. Indian J Radio Space Phys 2013, 42(2), 73-81.

Aims at investigating the relationship between F2 layer critical frequency (foF2) and solar activity indices viz. smoothed twelve-month running mean of the sunspot number (R12) and the solar radio flux of 10.7cm wavelength (F10.7) during three different solar epochs. Data from Ouagadougou, an African low latitude station (latitude 12.4°N, longitude 1.5°W, dip 5.7), and the National Geophysical Data Centre were used for the study. Distinct characteristics were observed during different solar epochs and during each season. Sunspot number and solar radio flux agreed better during the year of moderate solar activity than during the year of low solar activity. The average correlation coefficients between foF2 and F10.7 obtained for high, moderate and low solar activity were 0.17, 0.67, and 0.44, respectively; while correlation coefficients between foF2 and R12 obtained were 0.05, 0.66, and 0.49, respectively. Irrespective of solar epochs and the trend of the indices, a trough in foF2 value was observed towards the end of June solstice. Relationship between foF2 and the solar activity indices agreed reasonably for the three solar epochs during December solstice. A strong solar activity dependence of foF2 around equinoxes than solstices was also observed. Factors that could cause the F2 layer variation were discussed.

4 illus, 1 table, 32 ref

003204   Ehinlafa O E;Adeniyi J O (Physics Dep, University of Ilorin, Ilorin, Nigeria, Email: emmanolu4u@yahoo.com) : Comparison of observed h_mF2 and IRI 2007 model with M(3000)F2 estimation of h_mF2 during high solar activity for an equatorial station. Indian J Radio Space Phys 2013, 42(2), 82-8.

Ways of improving the equatorial F2 layer peak heights estimated from M(3000)F2 ionosonde data measured using the Ionospheric Prediction Service (IPS-42) sounder at Ouagadougou, Burkina Faso (geog lat +12.4°N, geog long +1.5°W, magnetic dip +5.9°N) during high solar activity year (1991) was investigated. For this purpose, the observed height of maximum electron density of F2 region (h_mF2_obs), deduced using an algorithm from scaled virtual heights of quiet day ionograms; and the predicted h_mF2 values, which is given by the IRI 2007 model (h_mF2_IR12007) have been compared with the ionosonde measured M(3000)F2 estimation of the h_mF2 values (h_mF2_est), respectively. A strong correlation with its coefficients R2 for all the seasons ranging 0.562 - 0.857 for h_mF2_obs values, and ranging 0.876 - 0.968 for the h_mF2_IR12007 values was observed in the linear regressions of h_mF2_obs and h_mF2_IR12007 with M(3000)F2 inverse. During the nighttime, estimated h_mF2 (h_mF2_est) was found to be positively correlated with the h_mF2_obs values by the post-sunset peak representation, which is not represented by the h_mF2_IR12007 values. Also, the validity of the h_mF2_est values has been investigated by finding the percentage deviations when compared with the h_mF2_obs and h_mF2_IR12007.

5 illus, 26 ref

003203   Rajeevan M;Madhulatha A;Rajasekhar M;Bhate J; Kesarkar A;Rao B V A (National Atmospheric Research Lab, Dep of Space, , Gadanki-517 112, Email: rajeevan@narl.gov.in) : Development of a perfect prognosis probabilistic model for prediction of lightning over south-east India. J Earth Syst Sci 2012, 121(2), 355-71.

Prediction model based on the perfect prognosis method was developed to predict the probability of lightning and probable time of its occurrence over the south-east Indian region. In the perfect prognosis method, statistical relationships are established using past observed data. For real time applications, the predictors are derived from a numerical weather prediction model. In the study, developed the statistical model based on Binary Logistic Regression technique. For developing the statistical model, 115 cases of lightning that occurred over the south-east Indian region during the period 2006-2009 were considered. The probability of lightning (yes or no) occurring during the 12-hour period 0900-2100 UTC over the region was considered as the predictand. The thermodynamic and dynamic variables derived from the NCEP Final Analysis were used as the predictors. A three-stage strategy based on Spearman Rank Correlation, Cumulative Probability Distribution and Principal Component Analysis was used to objectively select the model predictors from a pool of 61 potential predictors considered for the analysis. The final list of six predictors used in the model consists of the parameters representing atmospheric instability, total moisture content in the atmosphere, low level moisture convergence and lower tropospheric temperature advection. For the independent verifications, the probabilistic model was tested for 92 days during the months of May, June and August 2010. The six predictors were derived from the 24-h predictions using a high resolution Weather Research and Forecasting model initialized with 00 UTC conditions. During the independent period, the probabilistic model showed a probability of detection of 77% with a false alarm rate of 35%. The Brier Skill Score during the independent period was 0.233, suggesting that the prediction scheme is skillful in predicting the lightning probability over the south-east region with a reasonable accuracy.

7 illus, 5 tables, 35 ref

002237   Shylaja B S (NO, , Jawaharlal Nehru Planetarium, T Chowdaiah Road, High Grounds, Bangalore-560 001, Email: shylaja.jnp@gmail.com) : What is transit?. Resonance 2012, 17(5), 487-92.

The event of Venus passing in front of the Sun is called the transit. This is equivalent to an eclipse with the Moon replaced by the planet Venus. In this article, the rarity and importance of the event and the historical explorations are discussed.

4 illus, 3 ref

001164   Padmanabhan T (IUCAA, Post Bag 4, Pune Campus Univ, Ganeshkhind, Pune-411 007, Email: paddy@iucaa.ernet.in) : Measuring the heavens. Resonance 2012, 17(1), 6-10.

Authors improved telescope gave Huygens a better vision of the sky, but his ideas about light lay buried for a century. After the Copernican Revolution, physics - or 'natural philosophy' as it was then called - was taking rapid strides with contributions from Descartes, Torricelli, Boyle, Pascal and many others. One of the important contributions to physics and astronomy in the later half of the 17th century came from Christian Huygens (1629-1695) from the Netherlands. Unfortunately, the importance of his work was overshadowed by the towering dominance of Newton's work.

6 illus, 2 ref

001163   George L T;Sudheesh C;Lakshmibala S; Balakrishnan V (NO, Raman Research Institute, Bangalore-560 080) : Ehrenfest's theorem and nonclassical states of light Ehrenfest's theorm in quantum mechanics. Resonance 2012, 17(1), 23-32.

When it was first enunciated, Ehrenfest's Theorem provided a necessary and important link between classical mechanics and quantum mechanics. Today, the content of the theorem is understood to be a natural and immediate consequence of the equation of motion for operators when quantum mechanics is formulated in the Heisenberg picture. Nevertheless, the theorem leads to useful approximations when systems with Hamiltonians of higher than quadratic order in the dynamical variables are considered. In this two-part article, authors use it to provide a convenient illustration of the differences between so-called classical and nonclassical states of radiation.

3 ref

000117   Thakur M K;Sinha T K (NO, K.S.R. Mahavidyalaya, Sarairanjan, Samastipur, Bihar) : Theoretical model of ionosphere of venus based on venus express (svedhem et al. 2009). Bull pure appl Sci-Sect F 2011, 31(1-2), 17-22.

VIRTIS-MIR,VERA SPICAV and ASPERA-4 measurements on Venus Express provide a valuable data for a systematic studies of Ionosphere of Venus. The present paper focuses on the development of a new theorical model of the ionosophere of Venus based on the new data of neutral species, temperature profile, magnetic pressure etecetra. The result obtained are found to be in good agreement with the results obtained in Venus Express Mission.

10 illus, 13 ref

000116   Sagar R;Omar A;Brijesh Kumar;Gopinathan M; Pandey S B;Bangia T;Pant J;Shukla V;Yadava S (NO, Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital-263 129, Email: aomar@aries.res.in) : The new 130-cm optical telescope at devasthal, Nainital. Curr Sci 2011, 101(8), 1020-3.

Modern Ritchey-Chretien Cassegrain 130-cm diameter optical telescope has been successfully installed at Devasthal, Nainital in the central Himalayan region. This location was chosen after carrying out extensive site surveys. The first images obtained with the telescope indicate that atmospheric seeing and sky darkness at Devasthal are nearly at values as measured during the site survey. The values of seeing and sky darkness are comparable to some of the best astronomical sites in the world. The 130-cm telescope is functional and observations can be carried out from the control centre at Devasthal or from the Manora Peak in Nainital. This telescope has started providing valuable data for a number of research projects and is expected to help meet part of the national requirement in optical observational astronomy from small-aperture ground-based telescopes.

3 illus, 7 ref

023131   Singh J;Ravindra B (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034, Email: jsingh@iiap.res.in) : Twin telescope observations of the sun at kodaikanal observatory. Bull Astr Soc India 2012, 40(1), 77-92.

Reports the design, fabrication and installation of a 'Twin Telescope' at Kodaikanal Observatory intended to augment the ongoing synoptic observations of the Sun that have been carried out since 1904. The telescope uses a 15 cm objective capable of taking Ca-K line filtergrams and photoheliograms in continuum of the full disk of the Sun simultaneously, at a frequency of 0.1 Hz using 2kx2k format CCD cameras. The telescope has been in operation since February 2008 and images are being obtained at a cadence of 5 min during normal observing periods. In case of solar activity, images of the active regions can be taken at a frequency of 1 Hz by restricting the field of view and spatial resolution. In this paper, we describe the telescope, instruments, image acquisition, data calibration and image processing. We also discussed a method of determining the network element and plage area index. The preliminary results show that while the network element covers about 30% of the disk, the percentage of the network element area index varies marginally with the seeing conditions during the day.

10 illus, 15 ref

023130   Sharma D K;Bardhan A;Rai J (Physics Dep, Manav Rachna College of Engineering, Faridabad-121 001, Email: dksharma.mrce@mrei.ac.in) : Ionospheric electron and ion temperatures response to seismic activity. Indian J Radio Space Phys 2013, 42(1), 18-26.

Connection between earthquake and ionosphere has been proposed in the last few decades. A number of hypotheses have been suggested as the earthquake precursory to reduce the hazard of life and property but could not succeed. In the present study, effort has been rnade to correlate the ionospheric temperature anomalies to seismic activities. The ionospheric electron and ion temperatures were measured with the help of Retarding Potential Analyzer (RPA) payload aboard the Indian SROSS-C2 satellite. The data is used for the period 1995-1998 in the altitude range 430-630 km over the Indian region. The details of seismic events during this period were downloaded from the United State Geological Survey (USGS) website. The normal day ion and electron temperatures have been compared to the temperatures recorded during the seismic event. It has been observed that there is significant enhancement in the electron and ion temperatures. The electron temperature was enhanced by 1.2 - 1.5 times compared to the average normal day electron temperature. However, the ion temperature was 1.1 - 1.3 times over the average normal day ion temperature. The satellite data was analysed for corresponding seismic event duration in such way that the other possible effects are eliminated.

5 illus, 2 tables, 29 ref

023129   Ravi Kiron V;Sriram K;Rao P V (Astronomy Dep, Osmania Univ, Hyderabad-500 007, Email: rkiron@gmail.com) : Photometric study of contact binaries V3 and V4 in NGC 2539. Bull Astr Soc India 2012, 40(1), 51-64.

CCD photometric observations of the eclipsing contact binaries (EW type) V3 and V4 of the cluster NGC 2539 were made in the B and V bands using the 2m telescope at the lUCAA-Girawali Observatory in India. The light curves have been obtained and using the Wilson-Devinney code, the combined photometric solutions have been presented here. The photometric solutions have revealed that both V3 and V4 are W-type contact binary systems with mass ratios of 0.806 and 1.001 respectively. Revised orbital periods, absolute masses and radii of the components have been obtained. New ephemerides indicate that the orbital periods of the variables have not changed much during the time span of the observations from 2003 to 2009. The estimated absolute parameters for the two variables V3 and V4 are in close agreement with the field EW-type binaries (Gazeas & Stepien 2008). The distance estimate for V3 is 1712±48pc indicating that this could be a field star in the background of the cluster, while that for V4 is 1183±32pc, suggesting it to be a possible member of the cluster. No third light is found in the systems.

5 illus, 8 tables, 38 ref

023128   Pathania A;Lal A K;Chander Mohan;Medupe T (Physics and Electronics Dep, North-West Univ, Mafikeng, South Africa, Email: ankush.pathania@gmail.com) : Kippenhahn and Thomas averaging method for the structure of rotating stars. Bull Astr Soc India 2012, 40(1), 41-50.

In 1970, Kippenhahn and Thomas proposed an averaging technique to study the equilibrium structures of the rotationally and tidally distorted stars. This technique has been subsequently used in the literature by various authors to study the equilibrium structures, evolutionary tracks and oscillations of rotating stars and stars that are rotationally and tidally distorted (that is, stars in binary systems). In this review paper, author have tries to see how this technique has been used by different authors in studying the various problems of rotating stars and stars in binary systems and also, how it has been modified over many years in the face of certain challenges and problems arising in the field of stellar structure and evolution.

94 ref

023127   Oron S;D'ujanga F M;Ssenyonga T J (Physics Dep, Makerere Univ, Kampala, Uganda, Email: soron@physics.make.ac.ug) : Ionospheric TEC variations during the ascending solar activity phase at an equatorial station, Uganda. Indian J Radio Space Phys 2013, 42(1), 7-17.

The total electron content (TEC) is a vital and most dominant ionospheric parameter that can cause Global Positioning System (GPS) signal delays, signal degradation and in extreme cases loss of lock. This results into inefficient operations of ground and space based Global Navigation Satellite System (GNSS) applications. The study of TEC variability is, therefore, useful for GNSS users in order to minimize errors where high levels of accuracy in measurements are required. This paper presents the diurnal, seasonal and solar activity dependence of TEC at the GPS-SCINDA (Scintillation Network Decision Aid) station in Kampala, Uganda (geographic coordinates: latitude 0.3°N, longitude 32.6°S; and geomagnetic coordinates: latitude -9.3°, longitude 104.2°) for the years 2010 and 2011. The results obtained show that the diurnal variability in TEC at this station has a pre-dawn minimum followed by an early morning steady increase, an afternoon maximum and then a post sunset gradual reduction in TEC, with the equinoctial months depicting nighttime enhancements more prominently at around 2000 hrs UT (2300 hrs LT). Scintillation occurrence, a consequence of TEC fluctuations, was observed from about 1800 hrs UT (2100 hrs LT) to local midnight giving S₄ index values above 0.4, with the equinox months recording higher occurrences than other seasons. TEC variations were also seen to exhibit solar activity dependence. The sunspot numbers and the F10.7 solar flux exhibited a good correlation with TEC recorded over the two years.

7 illus, 21 ref

023126   Kanekar N (Ramanujan Fellow, National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune Campus Univ, Ganeshkhind, Pune-411 007, Email: nkanekar@ncra.tifr.res.in) : Do the fundamental constants change with time?. Bull Astr Soc India 2012, 40(1), 21-40.

Comparisons between the redshifts of multiple spectral transitions from distant galaxies provide a sensitive probe of secular changes in fundamental constants like the fine structure constant and the proton-electron mass ratio. This article discusses the pros and cons of the various techniques that have been used to test for such changes, and summarizes the current status of the field and the directions for progress with upcoming radio and optical telescopes.

125 ref

023125   Das S;Maitra A;Shukla A K (S K Mitra Centre for Research in Space Environment, Institute of Radio Physics and Electronics, Calcutta Univ, Kolkata-700 009, Email: das.saurabh01@gmail.com) : Diurnal variation of slant path Ka-band rain attenuation at four tropical locations in India. Indian J Radio Space Phys 2013, 42(1), 34-41.

Rain attenuation is very severe at Ka and higher frequencies especially in tropical regions. The conventional fade mitigation techniques are not be able to mitigate this severe fade and hence, suitable diversity technique is required for this purpose. In this paper, rain characteristics and slant path rain attenuation at 30 GHz using synthetic storm technique has been presented. Three years of high resolution rain rate data obtained from disdrometer at four tropical and equatorial locations in India have been utilized. The results indicate that the fade margin requirement is very high (above 50 dB at 30 GHz) for 99.99% link availability for these locations. However, the diurnal analysis shows that in most of the places, the rain occurrence is much less in morning/early-morning hours and therefore, the fade margin requirement will be considerably lower (around 30 dB at 30 GHz) in the morning hours compared to the afternoon hours. The result indicates the suitability of using selective time period for high link availability data communication over the locations studied.

4 illus, 2 tables, 32 ref

023124   Aryal B;Yadav S N;Saurer W (NO, Institute of Astro- and Particle Physics, Innsbruck Univ, Technikerstrasse 25 A-6020 Innsbruck, Austria, Email: binil.aryal@uibk.ac.at) : Spatial orientation of galaxies in the zone of avoidance. Bull Astr Soc India 2012, 40(1), 65-76.

Presents spatial orientation of spin vectors of galaxies found in the region 20° ≤ 80°, -10° ≤ b ≤ -5° in the first Palomar Observatory Sky Survey. The inclination angle and intrinsic flatness of a galaxy are used to determine the spin vector and spin vector projections of the galaxy. We studied the preferred alignments of spin vectors of galaxies with respect to equatorial, Galactic and supergalactic coordinate systems. Carried out Kolmogorov-Smirnov (K-S), Kuiper-V and Fourier tests in order to examine non-random effects. It is found that the spin vectors of galaxies tend to lie in the equatorial plane whereas these vectors tend to be oriented perpendicular the Local Supercluster plane. A random alignment of spin vectors of galaxies is noticed with respect to the Galactic plane. Possible explanation of the results are discussed.

4 illus, 39 ref

022032   Thyagarajan S (NO, Amity Institute of Space Science and Technology, ) : DEM processing methods. J Remote Sensing GIS 2013, 4(1), 13-28.

Digital elevation model (DEM) is used generically to mean the digital cartographic representation of the earth in any form, rectangular grids or lattices, triangular networks or irregular spot heights, and breaklines. This paper aims to present a review of recent techniques used in satellite image processing, especially with focus on DEM processing. The reviewed approaches are classified according to the various techniques used in processing DEM, various filters used in denoising and despeckling of DEM images have been described in this paper. This review does not contemplate to go into details of particular algorithms or describe results of comparative experiments; rather a summary of more approaches and interesting parts are presented in this paper. The major goal of the paper is to provide a comprehensive reference source for the researchers involved in processing of DEM.

10 illus, 21 ref

021052   Shiv Mohan;Das A;Chakraborty M (NO, Space Applications Centre, Ambawadi Vistar, P.O. Ahmedabad-380 015, Email: shivmohan@sac.isro.gov.in) : Polarimetric properties of lunar surface using mini-SAR data. Curr Sci 2011, 101(2), 159-64.

Lunar surface properties at both polar and equatorial regions were studied using data from the miniaturized synthetic aperture radar (Mini-SAR) on-board Chandrayaan-1. The Mini-SAR sensor was operated at the S-band (2.38 GHz) with left circular polarization for transmission, and horizontal and vertical polarizations for reception. The returned signal was stored in planetary data system format, where each pixel in an image strip was represented by the corresponding Stokes vectors. The study showed that circular polarization ratio, which is an important parameter that represents scattering associated with planetary ice as well as dihedral reflection, was anomalously high inside some of the craters in the polar regions. Other Stokes parameters such as degree of polarization (m) and LH-LV relative phase (8) also showed distinctly different types of scattering mechanisms inside and outside the craters on the lunar surface.

5 illus, 4 tables, 10 ref

021051   Sharaf M A;Selim H H;AlJehani B F;Alaqal L A (Astronomy Dep, Faculty of Science, King Abdul Aziz Univ, Jeddah, Saudi Arabia, Email: sharf_adel@hotmail.com) : Final state predictions for J2 gravity perturbed motion of the earth's artificial satellites using orthogonal curvilinear coordinates. Bull pure appl Sci-Sect E 2012, 31(2), 137-51.

Initial value problem for dynamical astronomy will be established using four orthogonal curvilinear coordinates: Spherical Polar, Prolate Spheroidal, Bipolar and Bispherical coordinates. A computational algorithm is developed for the finial state predictions for J2 gravity perturbed motion of the Earth's artificial satellites using these orthogonal curvilinear coordinates. This algorithm is important in targeting, rendezvous maneuvers as well for scientific researches. The applications of the algorithm are illustrated by numerical examples of some test orbits of different eccentricities. The numerical results are extremely accurate and efficient.

5 tables, 5 ref

021050   Sharaf M A;Abouelmagd E I (Astronomy Dep, Faculty of Science, King Abdul Aziz Univ, Jeddah, Saudi Arabia, Email: sharaf_adel@hotmail.com) : The equations of motion for photogravitional and oblateness in elliptic restricted three body problem in terms of regularized Levi-Civita variables. Bull pure appl Sci 2012, 31(1), 129-35.

Equations of motion for photogravitional and oblateness in elliptic restricted three body problem was established in terms of the regularized Levi-Civita variables. Author considered the case in which, the bigger primary is spherical as well as the source of radiation, while the smaller primary is oblate spheroid.

8 ref

021049   Marvin Herndon J (NO, Transdyne Corporation, 11044 Red Rock Drive, San Diego, CA 92131, USA, Email: mherndon@san.rr.com) : Potentially significant source of error in magnetic paleolatitude determinations. Curr Sci 2011, 101(3), 277-8.

1 illus, 8 ref

019972   Paul D;Das H S;Sen A K (Physics Dep, Assam Univ, Silchar-788 011, Email: hsdas@iucaa.ernet.in) : Imaging polarimetry of the bok globule CB56. Bull Astr Soc India 2012, 40(2), 113-19.

Measurement of polarization of the background stars in the region of Bok globules is important to study the magnetic field geometry and dust grain characteristics in the globule. These parameters are important for the formation and evolution of dark clouds. We made polarimetric observations of Bok globule CB56 in the R-filter from the 2-metre telescope at IUCAA Girawali Observatory (IGO). The observations were carried out on 2011 March 4th and 5th. The CCD images obtained from the instrument (IFOSC) were analyzed, to produce the polarization map of the Bok globule CB56.

1 illus, 4 tables, 27 ref

019971   Paul B;Archana M;Saripalli L (NO, Raman Research Institute, Sadashivnagar, C.V. Raman Avenue, Bangalore-560 080, Email: bpaul@rri.res.in) : Simultaneous X-ray and optical observations of thermonuclear bursts in the LMXB EXO 0748-676. Bull Astr Soc India 2012, 40(2), 93-103.

Author reported the detection of a large number of optical bursts in the Low Mass X-ray Binary (LMXB) EXO 0748-676 simultaneous with the thermonuclear X-ray bursts. The X-ray and the optical bursts are detected in a long observation of this source with the XMM-Newton observatory. This has increased the number of thermonuclear X-ray bursts in the LMXBs with simultaneous optical detection by several factors. The optical bursts are found to have a linear rise followed by a slow, somewhat exponential decay. Most of the optical bursts have longer rise and decay timescale compared to the corresponding X-ray bursts. We have determined the X-ray and optical excess photon counts in the bursts that allow us to look at the optical to X-ray burst fluence ratio for each burst and the ratio as a function of the X-ray burst intensity and as a function of the orbital phase. The delay between the onset of the X-ray bursts and the onset of the optical bursts have also been measured and is found to have an average value of 3.25 seconds. Not find any convincing evidence of orbital phase dependence of the following parameters: X-ray to optical delay, rise time of the optical bursts, and optical to X-ray burst intensity ratio as would be expected if the optical bursts were produced by reprocessing from the surface of the secondary star that is facing the compact star. On the other hand, if the optical bursts are produced by reprocessing of the X-rays in the accretion disk, the onset of the bursts is not expected to have a sharp, linear shape as is observed in a few of the bursts in EXO 0748-676. Emphasises the fact that simultaneous optical observations of the X-ray bursts in multiple wavelength bands will enable further detailed investigations of the reprocessing phenomena, including any non-linear effect of the X-ray irradiation.

4 illus, 25 ref

019970   Nandi S;Saikia D J (NO, Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital-263 129, Email: sumana@aries.res.in) : Double-double radio galaxies from the first survey. Bull Astr Soc India 2012, 40(2), 121-37.

Radio structures and optical identifications of a sample of 242 sources classified as double-double radio sources by Proctor (2011) from a morphological study of sources in the FIRST (Faint Images of the Radio Sky at Twenty centimeters) survey (2003 April release, 811,117 entries) have been examined. We have been able to confirm only 23 of these as likely to be double-double radio galaxies (DDRGs), whose structures could be attributed to episodic nuclear activity in their host galaxies. A further 63 require either higher-resolution radio observations or optical identifications to determine whether these are DDRGs. The remaining sources are unlikely to be DDRGs. We have examined the luminosities, sizes and symmetry parameters of the DDRGs and the constraints these place on our understanding of these sources.

5 illus, 5 tables, 28 ref

019969   Jevtic D;Dojcinovic I P;Tapalaga I;Puric J (Belgrade Univ, Faculty of Physics, P.O. Box 44, 11000 Belgrade, Serbia, Email: irinel@ff.bg.ac.rs) : Stark width regularities of neutral potassium lines within different spectral series. Bull Astr Soc India 2012, 40(2), 151-60.

Effects of upper level ionization potential on Stark widths of different spectral series of neutral potassium have been studied and discussed in this paper. Proton impact contribution to the Stark broadening show similar dependences as that of electron impact contribution. It is also shown that the term structure influences the Stark widths. Higher correlation between the empirical parameters were found when the temperature was increased. The deviation of the lowest transition from 4p-nd series trend can be explained by absence of close perturbing states to the emitting state. After establishing these dependences, the relations found were used for prediction of Stark widths for the missed lines, thus avoiding complicated calculation procedures.

4 illus, 3 tables, 29 ref

019968   George S J;Stevens I R (Astrophysics Group, The Cavendish Laboratory, JJ Thomson Avenue, Cambridge Univ, Cambridge, CB3 0HE, UK, Email: sgeorge@mrao.cam./ac.uk) : Low-frequency GMRT observations of the magnetic Bp star HR Lup (HD 133880). Bull Astr Soc India 2012, 40(2), 105-11.

Author presented radio observations of the magnetic chemically peculiar Bp star HR Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the source is not detected but we are able to determine upper limits to the emission. The 647 MHz limits are particularly useful, with a 5a value of 0.45 mJy. Also, no large enhancements of the emission were seen. The non-detections, along with previously published higher frequency detections, provide evidence that an optically thick gyro-synchrotron model is the correct mechanism for the radio emission of HR Lup.

1 table, 30 ref

019967   Chandola Y;Sirothia S K;Saikia D J;Gupta N (NCRA, TIFR, Pune Campus Univ, Post Bag 3, Pune 411 007, Email: chandola@ncra.tifr.res.in) : Associated H_I absorption towards the core of the radio galaxy 3C 321. Bull Astr Soc India 2012, 40(2), 139-50.

Reported the results of Giant Metrewave Radio Telescope (GMRT) observations of Hi absorption towards the FRII radio galaxy 3C321 (J1531+2404), which is associated with an active galaxy interacting with a companion. The absorption profile towards the radio core is well resolved and consists three components, of which the two prominent ones are red-shifted by 186 and 235 km s^-1 relative to the optical systemic velocity. The neutral hydrogen column density towards the core is estimated to be N(Hi)=9.23xl0²¹(T_s/100)(f_c/1.0) cm^-2, where T_s and f_c are the spin temperature and covering factor of the background source respectively. Also presented radio continuum observations of the source with both the GMRT and the Very Large Array (VLA) in order to understand the properties of a plume of emission at an angle of <126>30° to the source axis. This feature appears to have a steep high-frequency spectrum. The current hotspots and jet are active and seen in X-ray emission. The spectral ages of the lobes are ≤ 26 Myr. Discussed the possibility that, the plume could be relic emission due to an earlier cycle of activity.

4 illus, 3 tables, 41 ref

017985   Jyoti L M;Sen S (NO, Positional Astronomy Centre, Kolkata, Email: l_lalmohan@rediffmail.com) : On the transit of venus 2012: method of computation for prediction of contact timings. Mausam 2012, 63(1), 113-22.

Transit of Venus over the solar disc is an extremely rare event. The phenomenon occurred last time on June 8, 2004 when the entire event was visible from all parts of India. Another Transit of Venus is going to occur on June 6, 2012, though the entire event will not be visible from India. The Positional Astronomy Centre publishes data on Transit of Mercury and Venus in its annual publication 'The Indian Astronomical Ephemeris'. In this paper an attempt has been made to provide documentation on the methodology for computation of contact timings of the event. Using the methodology, the geocentric contact timings and local contact timings for important places of India for the event of Transit of Venus of June 6, 2012 have been predicted. The result thus obtained for different geocentric phases of the event has been compared with the predicted timings published by The Nautical Almanac Office, United States Naval Observatory and NASA.

5 illus, 3 tables, 6 ref

016996   Larranaga A (National Astronomical Observatory, National Colombia Univ, Bogota, Colombia, Email: ealarranaga@unal.edu.co) : Rotating charged black hole solution in f (R) gravity. Pramana J Phys 2012, 78(5), 697-703.

In the context of f(R) theories of gravity, authors address the problem of finding a rotating charged black hole solution in the case of constant curvature. A new metric is obtained by solving the field equations and we show that its behaviour is typical of a rotating charged source. In addition, authors analyse the thermodynamics of the new black hole. The results ensure that the thermodynamical properties in f(R) gravities are qualitatively similar to those of standard General Relativity.

9 ref

013002   Tout C A (Institute of astronomy, The Observations, Madingley Road, Cambridge CB3 OHA, England, UK, Email: cat@ast.cam.ac.uk) : Origin of the strongest magnetic fields in dwarfs. Pramana J Phys 2011, 77(1), 199-212.

White dwarfs have frozen in magnetic fields ranging from below the measurable limit of about 3 x 10³ to 10⁹ G. White dwarfs with surface magnetic fields in excess of 1 MG are found as isolated single stars and relatively more often in magnetic cataclysmic variables. Some 1253 white dwarfs with a detached low-mass main-sequence companion have been identified in the Sloan Digital Sky Survey (SDSS) but none of these shows sufficient evidence for Zeeman splitting of hydrogen lines for a magnetic field in excess of 1 MG. If such high magnetic fields in white dwarfs result from the isolated evolution of a single star then there should be the same fraction of high field white dwarfs among this SDSS binary sample as among single stars. Thus, we deduce that the origin of such high magnetic fields must be intimately tied to the formation of cataclysmic variables (CVs). The formation of a CV must involve orbital shrinkage from giant star to main-sequence star dimensions. It is believed that this shrinkage occurs as the low-mass companion and the white dwarf spiral together inside a common envelope. CVs emerge as very close but detached binary stars that are then brought together by magnetic braking or gravitational radiation. Author propose that the smaller the orbital separation at the end of the common envelope phase, the stronger the magnetic field. The magnetic cataclysmic variables (MCVs) originate from those common envelope systems that almost merge. Those common envelope systems that do merge are the progenitors of the single high field white dwarfs. Thus all highly magnetic white dwarfs, be they single stars or the components of MCVs, have a binary origin. This accounts for the relative dearth of single white dwarfs with fields of 10⁴-10⁶ G. Such intermediate-field white dwarfs are found preferentially in cataclysmic variables. The bias towards higher masses for highly magnetic white dwarfs is expected if a fraction of these form when two degenerate cores merge in a common envelope. From the space density of single highly magnetic white dwarfs we estimate that about three times as many common envelope events lead to a merged core as to a cataclysmic variable.

6 illus, 36 ref

013001   Sridhar S (Raman Research Institute, Sadashivanagar, Bangalore-560 080, Email: ssridhar@rri.res.in) : Magnetohydrodynamics turbulence: an astronomical perspective. Pramana J Phys 2011, 77(1), 185-98.

Early work on magnetohydrodynamic (MHD) turbulence in the 1960s due, independently, to Iroshnikov and Kraichnan (IK) considered isotropic inertial-range spectra. Whereas laboratory experiments were not in a position to measure the spectral index, they showed that the turbulence was strongly anisotropic. Theoretical horizons correspondingly expanded in the 1980s, to accommodate both the isotropy of the IK theory and the anisotropy suggested by the experiments. Since the discovery of pulsars in 1967, many years of work on interstellar scintillation suggested that small-scale interstellar turbulence must have a hydromagnetic origin; but the IK spectrum was too flat and the ideas on anisotropic spectra too qualitative to explain the observations. In response, new theories of balanced MHD turbulence were proposed in the 1990s, which argued that the IK theory was incorrect, and made quantitative predictions of anisotropic inertial-range spectra; these theories have since found applications in many areas of astrophysics. Spacecraft measurements of solar-wind turbulence show that there is more power in Alfven waves that travel away from the Sun than towards it. Theories of imbalanced MHD turbulence have now been proposed to address interplanetary turbulence. This very active area of research continues to be driven by astronomy.

50 ref

013000   Sheth R K (Center for Particle Cosmology, Pennsylvania Univ, Philadelphia, PA 19104, USA) : Symmetry in stochasticity: random walk models of large-scale structure. Pramana J Phys 2011, 77(1), 169-84.

This paper describes the insights gained from the excursion set approach, in which various questions about the phenomenology of large-scale structure formation can be mapped to problems associated with the first crossing distribution of appropriately defined barriers by random walks. Much of this is summarized in R K Sheth, A1P Conf. Proc. 1132, 158 (2009). So only a summary is given here, and instead a few new excursion set related ideas and results which are not published elsewhere are presented. One is a generalization of the formation time distribution to the case in which formation corresponds to the time when half the mass was first assembled in pieces, each of which was at least 1/n times the final mass, and where n ≥ 2; another is an analysis of the first crossing distribution of the Ornstein-Uhlenbeck process. The first derives from the mirror-image symmetry argument for random walks which Chandrasekhar described so elegantly in 1943; the second corrects a misuse of this argument. Finally, some discussion of the correlated steps and correlated walks assumptions associated with the excursion set approach, and the relation between these and peaks theory are also included. These are problems in which Chandra's mirror-image symmetry is broken.

7 illus, 18 ref

012999   Sengupta S;Marley M S (Indian Institute of Astrophysics, , Koramangala 2nd Block, Bangalore-560 034, Email: sujan@iiap.res.in) : Multiple scattering polarization- application of Chandrasekhar's formalisms to the atmosphere of brown dwarfs and extrasolar planets. Pramana J Phys 2011, 77(1), 157-68.

Chandrasekhar's formalisms for the transfer of polarized radiation are used to explain the observed dust scattering polarization of brown dwarfs in the optical band. Model polarization profiles for hot and young directly imaged extrasolar planets are presented with specific prediction of the degree of polarization in the infrared. The model invokes Chandrasekhar's formalism for the rotation-induced oblateness of the objects that gives rise to the necessary asymmetry for yielding net non-zero disk integrated linear polarization. The observed optical polarization constrains the surface gravity and could be a tool to estimate the mass of extrasolar planets.

3 illus, 30 ref

012998   Ray S;Gangopadhyay T;Dey J;Dey M (Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, KwaZulu-Natal Univ, Durban 4000, South Africa) : Estimate of stellar masses from their QPO frequencies. Pramana J Phys 2011, 77(3), 571-9.

Kilohertz quasiperiodic oscillations (kHz QPOs) are observed in binary stellar systems. For such a system, the stellar radius is very close to the marginally stable orbit R_ms as predicted by Einstein's general relativity. Many models have been proposed to explain the origin of the kHz QPO features in the binaries. Here we start from the work of Li et al (Phys. Rev. Lett. 83, 3776 (1999)) who in 1999, from the unique millisecond X-ray pulsations, suggested SAX J1808.4-3658 to be a strange star, from an accurate determination of its rotation period. It showed kHz QPOs eight years ago and so far it is the only set that has been observed. We suggest that the mass of four compact stars SAX J1808.4-3658, KS 1731-260, SAX J1750.8-2900 and IGR J17191-2821 can be determined from the difference in the observed kHz QPOs of these stars. It is exciting to be able to give an estimate of the mass of the star and three other compact stars in low-mass X-ray binaries using their observed kHz QPOs.

1 illus, 2 table, 32 ref

012997   Rabiu A B;Abe O E;Adeniyi J O (Space Physics Laboratory, Physics Dep, Federal Technology Univ, Akure, Nigeria, Email: abeemman@yahoo.com) : Variability of the vertical extent of ionospheric E-layer over a station within equatorial anomaly region. Indian J Radio Space Phys 2012, 41(5), 536-42.

The variability of the vertical extent of the E-layer of the ionosphere (V_E) has been examined within the equatorial ionospheric anomaly region, taken as the difference between 90 km which is the assumed lower boundary of the layer and the virtual height values measured with an ionosonde at Ouagadougou in Burkina Faso, West Africa (geographic lat 12.4°N, long 1.5°W and magnetic dip 5.9°N) for low solar activity year 1985 and high solar activity year 1990. The vertical extent is a measure of the vertical altitude of E-region of the ionosphere. The vertical extent of the E-layer was observed to be high (36-40 km) at sunrise and sunset while low (18-22 km) at noon for both years. Seasonal variation shows that vertical extent of E-layer during the solar minimum (maximum) is higher in September (March) equinox and lower in March (September) equinox. The vertical extent of E-layer has been found to be an unstable membrane as it varied from hour to hour, day to day, month to month and season to season in response to the solar activity. The V_E is thicker in the low solar activity (26.30 ± 3.47 km) than the high solar activity (23.01 ± 2.62 km), which implies that increase/decrease in the solar activity results in decrease/increase in vertical extent of E-layer. Precisely, 5.4% (35.9%) variation in low (high) solar activity is accounted for by the variability in solar activity while the remaining percentage may be due to other factors.

10 illus, 1 table, 21 ref

012996   Padmanabhan T (Inter Centre for Astronomy and Astrophysics Univ, Pune Campus Univ, Ganeshkhind, Pune-411 007, Email: paddy@iucaa.ernet.in) : Statistical mechanics of gravitating systems ... and some curious history of Chandra's rare misses!. Pramana J Phys 2011, 77(1), 147-56.

Chandra's academic life had several phases each culminating in a monograph describing that subject. Author deal with aspects of his work in the two earliest phases and describe the overall structure of statistical mechanics of gravitating systems, the relevance of isothermal sphere in the mean-field approximation and issues related to collisional relaxation and dynamical friction in self-gravitating system of particles. There are several curious features in the history of these topics which comment upon.

1 illus, 14 ref

012995   Moodley J;Amery G (Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, KwaZulu-Natal Univ, Private Bag X54001, Durban 4000, South Africa, Email: sanjana.jm@gmail.com) : Investigation of embeddings for spherically symmetric spacetimes into Einstein manifolds. Pramana J Phys 2011, 77(3), 533-43.

Embeddings into higher dimensions are very important in the study of higher-dimensional theories of our Universe and in high-energy physics. Theorems which have been developed recently guarantee the existence of embeddings of pseudo-Riemannian manifolds into Einstein spaces and more general pseudo-Riemannian spaces. These results provide a technique that can be used to determine solutions for such embeddings. Here we consider local isometric embeddings of four-dimensional spherically symmetric spacetimes into five-dimensional Einstein manifolds. Difficulties in solving the five-dimensional equations for given four-dimensional spaces motivate us to investigate embedded spaces that admit bulks of a specific type. We show that the general Schwarzschild-de Sitter spacetime and Einstein Universe are the only spherically symmetric spacetimes that can be embedded into an Einstein space of a particular form, and we discuss their five-dimensional solutions.

25 ref

012994   Merritt D (Physics Dep, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, NY 14623, USA, Email: merritt@astro.rit.edu) : Stellar dynamics and black holes. Pramana J Phys 2011, 77(1), 135-46.

Chandrasekhar's most important contribution to stellar dynamics was the concept of dynamical friction. Here briefly review that work, then discuss some implications of Chandrasekhar's theory of gravitational encounters for motion in galactic nuclei.

^iia3 illus, 19 ref

012993   Maharaj S D;Lortan D B (Astrophysics and Cosmology Unit, School of Mathematical Sciences, Kwazulu- Natal Univ, Private Bag X54001, Durban 4000, South Africa, Email: maharaj@ukzn.ac.za) : Charged fluids with symmetries. Pramana J Phys 2011, 77(3), 477-82.

Investigate the role of symmetries for charged perfect fluids by assuming that spacetime admits a conformal Killing vector. The existence of a conformal symmetry places restrictions on the model. It is possible to find a general relationship for the Lie derivative of the electromagnetic field along the integral curves of the conformal vector. The electromagnetic field is mapped conformally under particular conditions. The Maxwell equations place restrictions on the form of the proper charge density.

13 ref

012992   Kane R P (Instituto Nacional de Pesquisas Espaciais-INPE, C P 515, Sao Jose dos Campos, 12245-970 SP, Brazil, Email: kane@dge.inpe.br) : Cosmic ray forbrush decreases after the giant solar flare of 15 february 2011. Indian J Radio Space Phys 2012, 41(5), 520-3.

Very strong X-ray solar flare occurred at about 0200 hrs UT on 15 February 2011. It was associated with a coronal mass ejection (CME) but the CME was not very strong and its interplanetary CME (ICME) took about 70 h to reach the Earth. Also, the ICME blob had a moderate, short-lived magnetic field B, so the resulting cosmic ray Forbush decrease (FD) was weak. The Bz component was only slightly negative, so the resulting geomagnetic storm magnitude Dst was negligibly small. Thus, this giant solar flare had very poor geo-effectiveness indicating that large flares need not necessarily lead to significant storm effects on Earth, particularly in the early part of a sunspot cycle when overall solar activity would be weak.

1 illus, 1 table, 9 ref