004163   Joshi J G;Pattnaik S S;Devi S;Lohokare M R (ETV and ECE Dep, National Institute of Technical Teacher Training and Reseach, Chandigarh-160 019, Email: shyampattnaik@yahoo.com) : Frequency switching of electrically small patch antenna using metamaterial loading. Indian J Radio Space Phys 2011, 40(3), 159-65.

A frequency switchable planar metamaterial loaded electrically small microstrip patch antenna, capable of resonating at different frequencies by varying the loading distance, has been presented in this paper. The rectangular microstrip patch antenna is loaded with planar metamaterial square spilt ring resonators (SRRs) in three different configurations at a distance of 0.25, 0.50 and 0.75 mm, respectively to get the switchable resonant frequency performance. The square SRRs reveals negative permeability (μ) presenting the single negative metamaterial (SNG) characteristics. The unloaded rectangular microstrip patch antenna resonates at 23 GHz. In loading condition at different distances, the rectangular microstrip patch antenna resonates at 9.61, 9.51 and 9.41 GHz, respectively. Using Chu limit, size of the antenna, that is ka, reaches 0.766, 0.775 and 0.787 in respective configurations, thus, satisfies the condition ka <60> 1 for electrically small antenna. The resonant frequency of rectangular microstrip patch antenna decreases with respect to the loading distance due to magnetic coupling. As the loading distance gets reduced, the mutual inductance increases resulting in enhancement of the bandwidth of the antenna. In these three loading conditions, the radiation quality factor (Q_rad) is larger than the minimum Q that is Q_chu. The directivity is more than 7.50 dBi in the presented configurations of electrically small rectangular microstrip patch antenna.

8 illus, 18 ref

004162   Akala A O;Somoy E O;Rabiu A B (Physic Dep, Univ of Lagos, Akoka, Yaba, Lagos, Nigeria, Email: akalaovie2004@yahoo.com ) : Ionospheric foF2 variability at equatoial and low latitudes during high, moderate and low solar activity. Indian J Radio Space Phys 2011, 40(3), 124-9.

This paper presents diurnal, seasonal and solar activity effects on the variability of ionospheric foF2 in the equatorial and low latitude regions. Three ionosonde stations, viz. Huancayo (12.0°S, 75.3°W, dip 1.8°N), Ouagadougou (12.4°N, 1.5°W, dip 2.8°N) and Vanimo (2.7°S, 141.3°E, dip 22.5°S) were considered for the investigation. Generally, the diurnal analysis revealed that the critical frequency of the F2 layer (foF2) is more susceptible to variability during the nighttime than the daytime, with two characteristic peaks, pre-sunset peak (12-50%) and post-midnight peak (22-70%). Seasonally, the June Solstice maximum was observed at Vanimo, while the peaks for other seasons were observed at Huancayo with the overall non-typical pattern of seasonal characterization for foF2 variability. At all stations, foF2 variability was noticed to be highest for the low solar activity year. Overall, equatorial foF2 variability increases with decreasing solar activity.

4 illus, 22 ref

002089   Rakesh Chandra N;Yellaiah G;Vijaya Bhaskara Rao S (NO, Nishitha College of Engineering and Technology, Lemoor (V), Email: rakeshnarwa@gmail.com) : MST radar observations of the leonid meteor storm during 1996-2007. Indian J Radio Space Phys 2011, 40(2), 67-71.

The Indian MST radar is a powerful atmospheric remote sensing instrument for ionospheric studies operating at 53 MHz frequency. Systematic observations of Leonids were carried out during 16-20 November every year from 1996 to 2007 with radar operating in meteor mode. It has been observed that the presence of strong background component which resulted from several apparitions of parent comet is the cause for the shower activity every year. The trail component that was left behind during each apparition is strong enough to cause the meteor shower for two consecutive years. In this regard, the detailed study of 2007 Leonids is presented in the paper, even though the shower activity was observed to be quite low, and interestingly it resulted in a double (multiple) broad peak rather than a single peak. The results show that the Leonid stream composed of several narrow dense trails existed simultaneously and the sharp meteor outbursts were observed when the Earth encountered a region of high spatial density of particles within the stream.

5 illus, 7 ref

002088   Kane R P (NO, Instituto Nacional de Pesquisas Espacias, INPE C P 515 12201-970 Sao Jose dos Campos, SP, Brazil, Email: dane@dge.inpe.br) : Directional muon telescopes not useful for estimating the magnitudes of forbush decreases and geomagnetic storms. Indian J Radio Space Phys 2011, 40(2), 74-84.

When a coronal mass ejection (CME) escapes from the Sun and spreads in interplanetary space as a blob (termed as interplanetary CME, ICME), galactic cosmic rays (CR) passing through the same get modulated and one can detect anisotropies in data of muon directional telescopes located on the Earth. For 15 severe storms (Dst <60> -200 nT) during solar cycle 23 (1996-2006), the hourly data for Nagoya muon directional telescopes showed that for each one of these storms, there were anisotropies in one or more of the 16 directional telescopes. The maximum magnitudes of the anisotropies were <126>% or less and had reasonably good relationships (correlation +0.75) with the magnitudes of the following Forbush decrease (FD) in the muons in the vertical direction V (muon V) and also in CR neutron monitor (NM) data at Climax, Colorado, USA. But a correlation of <126>0.75 implies a variance explained (square of correlation) of only <126>55%, leaving <126>45% as random component. With geomagnetic Dst(min), the muon anisotropy magnitudes had a still lower correlation (+0.44±0.20), which would imply a variance explained of only <126>20%, leaving <126>80% as random component, resulting in regression prediction errors exceeding 50%. Thus, the anisotropies were only a rough indicator of there being some anomalous structure out in the interplanetary space, but the magnitudes of the anisotropies could not give any accurate indication of the magnitudes of the Forbush decreases that may follow, much less for the magnitudes of the geomagnetic storm Dst(min) that may follow.

s, 2 tables, 39 ref

002087   Kane R P (NO, Instituto Nacional de Pesquisas Espacias, INPE C P 515 12201-970 Sao Jose dos Campos, SP, Brazil, Email: dane@dge.inpe.br) : Prediciton of the size of coming solar cycle 24 based on solar parameters during sunspot minimum between cycles 23 and 24. Indian J Radio Space Phys 2011, 40(2), 72-5.

The dependence of Rz(max) on preceding two solar parameters, namely length of sunspot minimum and the values of Rz(min), has been examined in the present paper. The results indicate a prediction of Rz(max) = <126>90±20 for cycle 24. The average of cycles 1 -23 is about 115. So, the prediction here indicates sunspot activity below normal.

1 illus, 1 table, 17 ref

002086   Kane R P (NO, Instituto Nacional de Pesquisas Espaciais-INPE, C P 515, Sao Jose dos Campos, Brazil, Email: kane@dge.inpe.br) : Solar activity during sunspot minimum. Indian J Radio Space Phys 2011, 40(1), 7-10.

During the sunspot minimum years 2007-2009 of solar cycle 23, the sunspot number, Rz, declined from January 2007 till the end of 2007 and further till September 2009. But in between, there were sporadic increases during January, June, December 2007; March 2008; and September 2009. These were reflected very well in timing in the 2800 MHz solar radio emission flux F-10, X-ray background, and the occurrence frequency of coronal mass ejections (CME). Thus, all these have a major origin in the same active regions.

2 tables, 10 ref

002085   Ganesh K E;Umesh T K;Narasimhamurthy B (S&H BSK III Stage Dep, PES Institute of Technology, Bengaluru-560 084, Email: ganeshke@gmail.com) : Atmospheric turbidity over a continental station, Mysore, India. Indian J Radio Space Phys 2011, 40(2), 85-94.

The solar radiation is collected at five optical channels at a continental station Mysore, India during December 2003 -June 2006 using a portable sunphotometer MICROTOPS II. Angstrom's turbidity parameters, a and β, have been calculated and analysed on daily, monthly, seasonal and annual basis. The observations show that α and β vary throughout on individual day because of changes in the atmospheric meteorological parameters. It is observed that β is highest during summer and lowest during winter. An anti-correlation between α and β is observed throughout the day during all seasons indicating continuous redistribution of fine and coarse particles under the influence of meteorological parameters. The yearly comparison of α and β along with the atmospheric visibility is also analysed and presented in the paper.

11 illus, 2 tables, 22 ref

024627   Vadher N M;Shah A B;Jain R;Vats H O;Deshpande M R;Seetha S;Murthy;Sharma R K;Umapathy (NO, Physical Research Laboratory, Ahmedabad) : Instrumentation of "Solar X-ray Spectrometer" low energy detector (SLD) - proposed payload onboard Indian satellite. Bull Astr Soc India 2000, 28(1), 121-2.

It is proposed to fly a high spectral and temporal resolution - "Solar X-Ray Spectrometer (SOXS)" onboard Indian satellite. The SOXS will provide the disk integrated flux in the energy range 2 keV-10 MeV. It is composed of two detector modules - SOXS Low Energy Detector (SLD) and SOXS High Energy Detector (SHD). The SLD consists of state-of-the-art Silicon PIN and Cadmium-Zinc-Telluride detectors to study the energy spectra in 2-30 keV with sub-keV energy and 10 ms temporal resolution. Proposed instrumentation for SLD module consists of front-end electronics, Pulse-height analyser, DC to DC modules, house keeping parameters to monitoring logic and interfacing for SOXS Low Energy Processing Electronics (SLE) to SOXS Common Electronics (SCE). The SLE collects the data from the two detectors and process the data in temporal and spectral modes. The SLE is interfaced with Telemetry and SCE. The salient feature of SLD is real time formulation of spectra in four time intervals as commanded by processing electronics.

024626   Uddin W;Verma V K (NO, Uttar Pradesh State Observatory, Nainital-263 129) : Surge activities on November 26-28, 1990. Bull Astr Soc India 2000, 28(1), 125-8.

Study of 8 solar surges observed in H_α emission on the west solar limb (active region NOAA 6368) on 26, 27 and 28 November 1990. Three surges were observed on 26 November of durations 35, 86 and 40 min at the time intervals of 20 and 25 min respectively for successive events. Again in the same active region, observed two solar surges of durations 56 and 101 min on 27 November at an interval of 10 min. Three surges were also observed on 28 November of durations 25, 138 and 95 mins at the time intervals of 10 and 20 min respectively for successive events. Using photographic observations, studied the morphological behaviour and estimated the height, mass, radial velocity, mechanical energies and magnetic fields associated with the 8 surges. The x-ray and radio data observed during the surges are also included. The various parameters estimated from the observed data are discussed in light of solar surge theories.

024625   Subramaniam A;Ram Sagar (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034) : Globular cluster systems in giant elliptical galaxies : a probe for the galaxy formation and evolution. Bull Astr Soc India 2000, 28(1), 163-4.

Most of the globular clusters in the universe reside in giant elliptical galaxies. The number of GCs present in them is about a few thousands. Due to their large distances (≥ 10 Mpc), it is impossible to observe their individual members. However, their integrated light observations can be obtained and used to understand them. The observables of the globular cluster systems (GCS) such as luminosity and mass distributions, specific frequencies, metallicity distributions and kinematics can be related to the competing hypotheses for galaxy formation in situ, mergers, or accretions.

024624   Sreekantan B V (NO, National Institute of Advanced Studies, IISc Campus, Bangalore-560 012) : Possible Indian participation in a 10 metre optical telescope project : summary of the panel discussion. Bull Astr Soc India 2000, 28(1), 171-2.

024623   Singh J;Sakurai T;Ichimoto K;Hiei E (NO, National Astronomical Observatory, 2-21-1 Ohsawa, Mitaka, Tokyo 181-8588, Japan) : On the formation of a helmet streamer on January 24, 1992 at the south-west limb. Bull Astr Soc India 2000, 28(1), 33-45.

Analysed the soft X-ray images of the sun obtained with the YOHKOH satellite, white light coronal images observed at Mauna Loa and H-alpha pictures of the sun taken at Mitaka and Kodaikanal to study helmet streamers. Heating of a filament and subsequent brightening in X-rays, and eruption in the region lead to the formation of the helmet streamer on January 24, 1992. In another event of February 24, 1993, only the brightening and eruption-like expansion of the brightening in soft X-rays lead to the formation of the steamer. No H-alpha filament was seen in this region before and after the event of brightening in soft X-rays and formation of streamer on February 24, 1993. Postulate that the plasma in the streamer comes from the solar surface during the X-ray eruption, and magnetic field of the region perhaps helps in containing the plasma and the formation of the streamer.

024622   Singh H P;Roxburgh I W;Chan K L (Department of Physics, Sri Venkateswara College, New Delhi-110 021) : Convective overshooting in stellar interiors. Bull Astr Soc India 2000, 28(1), 81-4.

Region of turbulent convective motions in stellar envelopes provides for both energy transport and the redistribution of chemical elements by mixing processes. Penetration or overshooting of these convective motions into the surrounding stable layers extends the unstable region thereby influencing the mixing and hence the structure and evolution of stars. Different approaches to the study of convective overshooting with special emphasis on numerical simulations. Overshooting from convective cores is also discussed.

15 ref

024621   Sahni V (NO, Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune-411 007) : Case for the cosmological constant. Pramana J Phys 2000, 55(1-2), 43-52.

The main motivation for invoking a small cosmological constant (or A-term) at the present epoch has to do with observations of high redshift Type Ia supernovae which suggest an accelerating universe. A flat accelerating universe is strongly favoured by combining supernovae observations with observations of CMB anisotropies on degree scales which give the `best-fit' values ΩΛ ≈ 0.7 and Ωm ≈ 0.3. A time dependent cosmological A-term can be generated by scalar field models with exponential and power law potentials. Some of these models can alleviate the `fine tuning' problem which faces the cosmological constant.

41 ref

024620   Saha L M;Khan A;Sarma T P (Department of Mathematics, Z.H. College, University of Delhi, J.L.N. Marg, New Delhi-110 002) : Effects of the solar radiation pressure and tidal forces on the rotational motion of a satellite. Bull Astr Soc India 2000, 28(1), 147-52.

Rotational motion of a satellite influenced by solar radiation pressure and tidal forces have been investigated. Melnikov's integral has been evaluated to establish the non-integrability of the equation of motion. The time series and poincare surface of section have been drawn for different ranges of values of solar radiation parameter, tidal parameter and eccentricity of the orbit to indicate the influence of these quantities.

024619   Sagar R;Mohan V;Pandey A K;Pandey S B;Castro Tirado A J (NO, U.P. State Observatory, Manora Peak, Nainital-263 129) : Temporal behaviour of emissions from γ-ray bursts and optical/near-IR afterglows of GRB 991208 and GRB 991216. Bull Astr Soc India 2000, 28(1), 15-31.

1CD magnitudes in Cousins R and I photometric passbands are determined for GRB 991216 and GRB 991208 afterglows respectively ″ 1 and ″ 3 day after trigger of the corresponding γ-ray bursts. Light curves of the afterglow emissions are obtained by combining the published data with the present measurements in R and I passbands for GRB 991208 and in R, Gunn i and J passbands for GRB 991216. They indicate that the flux decay constants of a GRB are almost the same in each passband with values ″2.2 for GRB 991208 and ″ 1.2 for GRB 991216 indicating very fast optical flux decay in the case of former which may be due to beaming effect. However, cause of steepening by 0.23 ± 0.06 dex in the R light curve of GRB 991216 afterglow between 2 to 2.5 day after the burst is presently not understood. Redshift determinations indicate that both GRBs are at cosmological distance with a value of 4.2 Gpc for GRB 991208 and 6.2 Gpc for GRB 991216. The observed fluence <62> 20 kev indicates, if isotropic, release of energy ″ 1.3 x 10⁵³ erg far GRB 991208 and ″ 6.7 x 10⁵³ erg for GRB 991216 by these bright γ-ray flashes. The enormous amount of released energy will be reduced, if the radiation is beamed which seems to be the case for GRB 991208 afterglow.

62 ref

024618   Ravindranath S;Prabhu T P (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Lyman break galaxies at high redshifts (Z <62> 3) as probes of galaxy formation. Bull Astr Soc India 2000, 28(1), 169-70.

Study of star-forming galaxies at high redshifts with large 10-m class telescopes. Lyman break galaxies serve as the best candidates to probe galaxy formation and evolution. The faintness of these objects (I₈₁₄ <62> 24) necessitates the use of large telescopes.

024617   Rautela B S;Joshi G C;Srivastava J B (NO, U.P. State Observatory, Manora Peak, Nainital) : Spectrophotometric observations of comet Hale Bopp (C/1995 O1). Bull Astr Soc India 2000, 28(1), 129-33.

Haser Model production rates of CN and C₂ in the coma of the comet Hale-Bopp (C/1995 O1) have been obtained. Molecular production rate, size of the nucleus and continuum flux at 484.0 nm have further been analysed to get the dust production rates. The comet appears to the dusty.

12 ref

024616   Rao M V;Samuel R;Nair P S;Ananthan A (Experimental Structures Division, Structures Group, ISRO Satellite Centre, Bangalore-560 017) : Laser interferometric techniques for non-destructive evaluation of spacecraft components. J Spacecraft Technol 2000, 10(1), 61-7.

Laser interferometric techniques find many applications in spacecraft component testing. Holographic Interferometry (HI) and Electronic Speckle Interferometry (ESI) are two such laser based interferometric techniques that are used in Structures Group for Non-Destructive Evaluation (NDE) of spacecraft components. Based on the experience gained, many new optical setups are being developed for the future needs. An overview of these techniques, optical setups and applications for various spacecraft components are presented.

16 ref

024615   Ram Sagar (NO, Uttar Pradesh State Observatory, Manora Peak, Nainital-263 129) : Distribution of stellar mass in young star clusters of our galaxy and nearby galaxies. Bull Astr Soc India 2000, 28(1), 55-62.

Stellar mass distribution in young star clusters in our Galaxy, the Magellanic Clouds and the nearby local groups of galaxies has been used to investigate the universality of initial mass function and presence of mass segregation in these systems. There is no obvious dependence of the MF slope on either galactocentric distance or age of the galactic open star clusters. A comparison of initial mass function slopes that have been measured in star clusters and associations of our and nearby galaxies indicates that the slope is independent of the spatial concentrations of the star formed, galactic characteristics including metallicity, and at least down to 0.85 M, the stellar mass range. Effects of mass segregation have been observed in good number of young stellar groups of galaxy and Magellanic Clouds. As their ages are much smaller than their dynamical evolution times, star formation processes seems to be responsible for the observed mass segregation in them.

44 ref

024614   Raja Reddy M (Solar Panel Division, Power Systems Group, ISRO Satellite Centre, Bangalore-560 017) : Solar array selection metholdology for high power communication satellites. J Spacecraft Technol 2000, 10(1), 52-60.

Concept of selection methodology is presented for selection of solar array for high power communication satellites. The methodology consists of a matrix approach in which applicable solar array with different solar cell candidates for high power GEO communication satellite are evaluated based on a number of selection criteria. These criteria represent attributes deemed essential for meeting the given mission requirements and ultimately, for the success of the entire mission. This approach allows the selection of systems based on all important factors rather than a single discriminator such as system mass or cost, which is often the case.

024613   Narayanan A S (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Magnetoacoustic gravity surface waves with flows. Bull Astr Soc India 2000, 28(1), 85-7.

Effect of uniform flows on the characteristics of magneto acoustic-gravity surface waves at a single interface when both the magnetic field and the propagation vector are parallel to each other is studied. The region above the interface is permeated by a uniform horizontal magnetic field. The lower region is field free. The temperature on both sides of the interface is assumed to be uniform, with a discontinuity along the interface. The dispersion relation for the fluid which is compressible and having large conductivity is derived in the linear context. Depending on the temperature structure, the interface supports one or two surface modes in the absence of gravity. Certain limiting cases are discussed.

024612   Lokanadham B;Yellaiah G;Kalyan Kumar J;Rao S B;Rao V C (Department of Astronomy, Osmania University, Hyderabad) : 1998 activity of leonid meteor shower. Bull Astr Soc India 2000, 28(1), 135-9.

Group of five observers have participated in visual, photographic and MST radar observations of Leonid meteor showed during 15-20 November 1998 at National MST Radar Facility (NMRF), Gadanki (13.47°N, 79.18°E) near Tirupati. The peak activity of the shower occurred at 00 : 00 hours UT on 17 November with a maximum rate of 450 per hour in visual and 1250 per hour in radar observations. These rates are very less compared to the rates observed during 1966 return of the shower. Simultaneous observations of Es occurrences during the shower period showed a spread of about 20-30 Km around 90 Km height region. Most of the Leonid meteor radar echoes occurred around 100 km range.

024611   KrishnaKumar V;Venkatakrishnan P;Srikanth R (NO, Indian Institute of Astrophysics, Bangalore) : Morphology of Ca II K bright points and their link to G band bright points. Bull Astr Soc India 2000, 28(1), 123-4.

Results of a preliminary analysis of a time series of a sequence of Ca II K bright points and G band bright points observed co-spatially and co-temporally. Inspection of these images shows that the larger Ca II K bright points occur between two G band bright points suggesting a loop structure with the top of the loop housing the Ca II K bright point. The velocities of the center of mass of G band pair and that of the corresponding K line bright point seem to be correlated even though these features appear at different heights in the solar atmosphere. The velocity of the K line bright point is estimated to lie between 0.5 km/sec to 5.0 km/sec, while that of G band bright points between 3.0 km/sec and 8.0 km/sec. The diffuse K line brightenings are found to trace out the boundary of photospheric granulation. Estimates the sizes of the cells enclosed by Ca II K brightenings.

024610   Javaraiah J (NO, Indian Institute of Astrophysics, Bangalore-560 034) : 4-day periodic variation in the Sun's meridional flow. Bull Astr Soc India 2000, 28(1), 95-6.

In latitude interval 20°-30°, the dependencies `initial' meridional motion, V_ini(τ), of sunspot groups with life spans τ = 2-12 days, on τ of the spot groups, and mean meridional motion, V(τ), of sunspot groups with τ = 10-12 days on age (t) of the spot groups, are often significant. The patterns of V_ini (τ) and V(t) are largely systematic and mutually similar, and suggest existence of a periodic variation in the solar meridional flow with period 4-day and amplitude 10-20 m s^-1. However, the relations of τ and t with depths of anchoring of magnetic structures of the spot groups suggest that the patterns of V_ini (τ) and V(t) may represent spatial structure of solar meridional flow in the Sun's convection zone, rather than temporal variation of the flow.

024609   Jain R;Rao A R;Dwivedi B N;Manoharan P K; Seetha S;Vahia M N;Vats H O;Venkatakrishnan P (NO, Physical Science Laboratory, Ahmedabad) : Science from "Solar X-ray Spectrometer (SOXS)" - proposed payload onboard Indian satellite. Bull Astr Soc India 2000, 28(1), 117-9.

It is proposed to fly a high spectral and temporal resolution "Solar X-ray Spectrometer (SOXS)" onboard Indian satellite to understand the mechanisms of energy release and particle acceleration in solar flares. The SOXS will provide the disk integrated flux in the energy range 2 keV-10 MeV. The proposed SOXS will consist of two detector modules - SOXS Low Energy Detector (SLD) and SOXS High Energy Detector (SHD). The proposed instrument will enable to measure precisely the low energy cut-off below 60 keV to estimate the total energy release in the flare. It is proposed that high spectral and temporal resolution efficiencies of detectors will reveal, perhaps for the first time, the observed break below 60 keV in the characteristic double power-law shape of hard X-ray spectrum. Whether electrons and protons are accelerated simultaneously may be also answered by correlating high temporal spectra of SLD and SHD. The high temporal and sub-keV resolution spectra from SLD will be capable to investigate the nature of micro/nano flares considered responsible to heat the chromosphere and corona. It is proposed to use the observations from this space borne instrument, along with extensive simultaneous ground based high spatial and time resolution observations in optical and radio wavebands for better understanding of the flare phenomena.

024608   Jain K;Tripathy S C;Brajesh Kumar;Bhatnagar A (NO, Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Udaipur-313 001) : Relation between frequency shift and the changes in activity indices. Bull Astr Soc India 2000, 28(1), 89-90.

Linear relation between the shift in p-mode frequencies and variation in two solar activity indices, namely the sunspot number and 10.7 cm radio flux. From this relation, an empirical model is constructed to estimate the mean frequency shifts with respect to activity index. Comparing the observed and estimated shifts for solar cycle 22 and comment on the systematic errors in different helioseismic data sets.

024607   Hiremath K M;Gokhale M H (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Fossil magnetic fields of the sun and stars. Bull Astr Soc India 2000, 28(1), 109-11.

Using helioseismologically inferred internal rotation given by Dziembowski et al., 1989, in the previous work, modelled the steady (fossil) part of the poloidal magnetic field structure as that which isorotates with the sun's internal rotation. The sun's internal rotation recently obtained by Antia et al., (1998), from the GONG data. The results of the work are almost similar to previous work but are much more accurate. It is important to note that it is possible to obtain a high degree of isorotation between an eigen-solution of the diffusion equation and the internal rotation inferred from the latest helioseismic data, by fitting only a few parameters in the eigen-solution. It is found that magnitude of the poloidal magnetic field varied substantially with the radial direction and is nearly independent of latitude.

024606   Giridhar S (NO, Indian Institute of Astrophysics, Bangalore-560 034) : High resolution spectroscopy with a 10-m class telescope. Bull Astr Soc India 2000, 28(1), 155-9.

17 ref

024605   Ghosh R N;Mishra B N (Dept. of Mathematics, Govt. Polytechnic, Gaya, Bihar) : Generalised photogravitational restricted three body problem. Bull Astr Soc India 2000, 28(1), 141-5.

Problem is generalised in the sence that the rigid spherical shell, filled with homogeneous, incompressible fluid is taken as on oblate spheroid and the second body is radiating outside the shell. The equations of motion of the problem has been found, which is different from Robe's. The locations and stability of collinear points of the problem have further been studied.

024604   Chitre S M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Helioseismology and solar neutrinos. Bull Astr Soc India 2000, 28(1), 71-4.

18 ref

024603   Brajesh Kumar;Tripathy S C;Jain R;Deshpande M R (NO, Udaipur Solar Observatory, Physical Research Laboratory, PO Box No. 198, Udaipur-313 001) : On the power and frequency of p-modes in sunspots. Bull Astr Soc India 2000, 28(1), 93-4.

Time series of GONG Dopplergrams has been used to measure the velocity fluctuations in the sunspot and quiet photosphere simultaneously. The power spectrum analysis show that the power of the predominant p-mode is reduced in the sunspot region by 36 to 51% as compared to the quiet photosphere. Results also show a relative frequency shift of the power envelope of these modes of the order of 70 to 300 μHz.

024602   Bhattacharjee P (NO, Indian Institute of Astrophysics, Koramangala,Bangalore-560 034) : Ultra high energy cosmic rays above 10<. Pramana J Phys 2000, 55(1-2), 297-305.

The observed cosmic ray events above 10¹¹ GeV are difficult to explain within the context of known physics of propagation of known particles in the Universe and within the standard acceleration mechanisms that are likely to operate in powerful astrophysical objects. Several ideas of possible new physics beyond the Standard Model have been suggested in order to explain these events.

37 ref

024601   Bhatnagar A;Jain K;Tripathy S C (NO, Udaipur Solar Observatory, Physical Research Laboratory, PO Box No. 198, Udaipur-313 001) : GONG p-mode frequency changes with solar activity. Bull Astr Soc India 2000, 28(1), 91-2.

Correlation study of nine solar activity indices with p-mode frequency shifts obtained from the GONG data. It is found that the two are closely correlated and a linear relationship exists. Further, the GONG p-mode frequencies for the period 1995 August to 1997 August show that the mean frequency decreases by 0.06 μHz during the descending phase of the solar cycle 22 and increases by 0.04 μHz in the ascending phase of the new solar cycle 23.

024600   Bhat P N (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Optical counter-parts of gamma ray bursts. Bull Astr Soc India 2000, 28(1), 165-7.

Gamma Ray Bursts (GRB's) being the most energetic astronomical phenomena known to date still pose a formidable challenge to astronomers. The BATSE on board the Compton Observatory (CGRO) launched in 1991, has shown that GRB's are unlikely to be of galactic origin. More recently, the launching of the X-ray satellites viz. Beppo SAX and RXTE enabled astronomers to locate GRB's rapidly and accurately leading to the discovery of their counter-parts in other wavelengths like X-ray, optical and radio. This has been a breakthrough in understanding the origin of GRB's. These observations led to the possibility of GRB's being extra-galactic in origin, the farthest source being at a redshift of ″ 5.0. The optical counter-parts of GRB's have been very faint and fading rapidly with time. This necessitates the use of a large optical telescope like the proposed 10m telescope (GTC). Discusses the need for a large telescope for GRB astronomy which can lead to discoveries resulting in the complete understanding of the origin of GRB's.

024599   Basu S (NO, Institute of Advanced Study, Olden Lane, Princeton N.J. 08540, U.S.A) : Helium abundance in the solar envelope. Bull Astr Soc India 2000, 28(1), 113-5.

024598   Basu S (NO, Institute of Advanced Study, Olden Lane, Princeton N. J. 08540, U.S.A) : Seismic sun. Bull Astr Soc India 2000, 28(1), 63-9.

"Seismic Sun" is a model of the Sun constructed using helioseismological deductions about the Sun. The seismic Sun is very similar to a standard solar model which incorporates gravitational settling of helium and heavy elements. The main discrepancy is just below the base of the convection zone and can be attributed to the lack of mixing in standard solar models.

27 ref

024597   Anupama G C (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Spectroscopy of supernovae. Bull Astr Soc India 2000, 28(1), 161-2.

024596   Antia H M;Chitre S M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Helioseismic constraints on the proton-proton reaction cross-section. Bull Astr Soc India 2000, 28(1), 105-7.

024595   Antia H M;Chitre S M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Effect of a magnetic field on solar oscillation frequencies. Bull Astr Soc India 2000, 28(1), 101-3.

024594   Antia H M;Basu S (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Effect of asymmetry in peak profile on f-mode frequencies. Bull Astr Soc India 2000, 28(1), 97-9.

024593   Antia H M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Rotation rate and flows in the solar interior. Bull Astr Soc India 2000, 28(1), 75-9.

Rotation rate in the solar interior can be inferred from measured splittings of solar oscillation frequencies using various inversion techniques. While other large scale flows can be studied using local techniques, like ring diagrams or time-distance helioseismology. These techniques can be used to study variation in flow velocities in the three spatial dimensions as well as the temporal variations.

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020143   Rajan Babu S;Gnanasekaran T;Ranganathan R; Periaswami G (Materials Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam) : Solubility of nickel chloride in molten sodium chloro aluminate. Bull Electrochem 2000, 16(1), 10-13.

Sodium metal chloride batteries operating in the temperature range of 523 K are being investigated extensively as high energy secondary storage systems. They use of sodium anode and transition metal chloride in liquid sodium chloroaluminate as cathode and beta alumina as solid electrolyte. While a lot of research effort had gone into investigating sodium beta alumina anode in course of development of sodium sulphur batteries, the relatively new metal cloride cathode in sodium chloroaluminate have not been extensively investigated. In this work the solubility of nickel chloride in basic sodium chloroaluminate over a temperature range of 448 to 523 K was measured to ascertain the chemical reversibility of nickel chloride cathode material. Electrochemical investigations on nickel electrode was also carried out to establish the electrochemical reversibility of nickel chloride cathodde. Half cell of configuration Ni/NaAlCl₄/Al was assembled and both high speed voltammetric and high resolution chronopotentiometric investigations were carried out in the temperature range of 448 to 523 K. Well defined symmetric cyclic voltammograms were obtained in te scan rate of 10 mvs^-1 to 10 Vs^-1. The voltammetric and chloropotentiometric investigations establish that the redox behaviour is governed only by diffusion in the time frame of the experiment....

020142   Knutsen H (NO, Stavanger College, Box 2557, Ullandhaug, N-4004 Stavanger, Norway) : Young universe. Phys Educ 2000, 16(4), 377-90.

016929   Pal P B (NO, Saha Institute of Nuclear Physics, 1/AF Bidhan-Nagar, Calcutta-700 064) : Determination of cosmological parameters : an introduction for non-specialists. Pramana J Phys 2000, 54(1), 79-91.

Defines the cosmological parameters H_o, Ω_m and Ω_∧. Then shows how the age of the universe depends on them, followed by the evolution of the scale parameter of the universe for various values of the density parameters. Then defines strategies for measuring them, and show the results for the recent determination of these parameters from measurements on supernovas of type 1a. Implications for particle physics is briefly discussed.

015879   Sagar R (NO, Uttar Pradesh State Observatory, Manora Peak, Nainital-263 129) : Importance of small and moderate size optical telescopes. Curr Sci 2000, 78(9), 1076-81.

Small and moderate size optical telescopes have advantages over large and giant ones in the areas of efficiency, availability, flexibility and serendipitous and speculative observations. Recent developments in astronomical detectors and instrumentation along with the growth in computers and softwares have increased their capabilities many-fold. They are therefore responsible not only for a number of recent discoveries in astronomy, e.g. detection of microlensing phenomenon, but also for providing valuable optical observations of celestial objects and phenomena discovered at other wavebands, such as radio, infrared, X-ray and γ-ray. All these factors make well-instrumented, small and moderate size optical telescopes highly relevant in contemporary astronomy despite competition from 6 to 10 m class ground-based optical telescopes and from the 2.3-m Hubble Space Telescope. Such telescopes in India have an added advantage of geographical location.

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015878   Narlikar J V (NO, Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune-411 007) : Cosmology : past, present and future. Curr Sci 2000, 78(9), 1071-6.

Technological achievements have helped the astronomer in better viewing the universe, a `final' understanding still eludes the search for the correct cosmological model. The article ends with a list of unsolved questions which the `future' may eventually answer.

015877   Dadhich N (NO, Inter University Centre for Astronomy & Astrophysics, P O Box 4, Pune-411 007) : Spherically symmetric empty space and its dual in general relativity. Curr Sci 2000, 78(9), 1118-20.

In the spirit of the Newtonian theory, spherically symmetric empty space in general relativity (GR) in terms of energy density is measured by a static observer and convergence density experienced by null and time-like congruences. It turns out that the space surrounding a static particle is entirely specified by the vanishing of energy and null convergence density. The electrograv-dual to this condition would be the vanishing of time-like and null convergence density which gives the dual-vacuum solution representing a Schwarzschild black hole with global monopole charge or with a cloud of string dust. Here the duality is defined by interchange of active and passive electric parts of the Riemann curvature, which amounts to interchange of the Ricci and Einstein tensors. This effective characterization of stationary vacuum works for the Schwarzschild and NUT solutions. The most remarkable feature of the effective characterization of empty space is that it leads to new dual spaces and the method can also be applied to lower and higher dimensions.

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013833   Vishveshwara C V (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034) : Black holes and rotation. J Astrophys Astr 1999, 20(3-4), 103-20.

Basic properties of the non-rotating Schwarzschild black hole and the rotating Kerr black hole Rotational effects are then described in static and stationary spacetimes with arial symmetry by studying inertial forces, gyroscopic precession and gravi-electromagnetism have been studied. The results are applied to the back hold spacetimes.

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013832   Stachel J (Department of Physics and Center for Einstein Studies, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 USA) : New light on the Einstein-Hillbert priority question. J Astrophys Astr 1999, 20(3-4), 91-101.

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