018340   Maurya R A;Ambastha A (Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Dewali, Badi Road, Udaipur-313 001, Email: ambastha@prl.res.in) : Hα intensity oscillations in large flares. J Astrophys Astr 2008, 29(1-2), 249-52.

Reinvestigate the problem of Hα intensity oscillations in large flares, particularly those classified as X-class flares. We have used high spatial and temporal resolution digital observations obtained from Udaipur Solar Observatory during the period 1998-2006 and selected several events. Normalized Lomb-Scargle periodogram method for spectral analysis was used to study the oscillatory power in quiet and active chro-mospheric locations, including the flare ribbons.

2 illus, 7 ref

018339   Maurya R A;Ambastha A (Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Dewali, Badi Road, Udaipur 313 001, Email: ramajor@prl.res.in) : Magnetic and velocity field variations in the active regions NOAA 10486 and NOAA 10488. J Astrophys Astr 2008, 29(1-2), 103-5.

Study the magnetic and velocity field evolution in the two magnetically complex active regions NOAA 10486 and NOAA 10488 observed during October-November 2003. Used the available data to examine net flux and Doppler velocity time profiles to identify changes associated with evolutionary and transient phenomena. In particular, we report detection of rapid moving features observed in NOAA 10486 during the maximum phase of the X17.2/4B superflare of October 28, 2003. The velocity of this moving feature is estimated around 40km/s, i.e., much greater than the usual Ha flare-ribbons' separation speed of 3-10km/s, but similar to the velocity of seismic waves, i.e., ± 45 km/s reported earlier by Kosovichev & Zharkova (1998).

2 illus, 5 ref

018338   Masuda S (Solar-Terrestrial Environment Laboratory, Nagoya Univ, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan, Email: masuda@stelab.nagoya-u.ac.jp) : Looptop impulsive hard X-ray source in solar flares observed with yohkoh/HXT. Asian J Phys 2008, 17(3-4), 411-21.

A new type of coronal hard X-ray source was first reported in 1994. That hard X-ray source was located above the soft X-ray loop and shows an impulsive behavior similar to those of the footpoint sources. Many solar physicists have tried to understand this source. However, still there remain many problems. The researches related to this source observed with Yohkoh/HXT are reviewed.

9 illus, 1 table, 25 ref

018337   Lozitsky V G;Staude J (NO, Kyiu Univ Astronomical Observatory, Observatorna St. 3, Kyiu, UA-04053, Ukraine, Email: lozitsky@observ.univ.kiev.ua) : Observational evidences for multi-component magnetic field structure in solar flares. J Astrophys Astr 2008, 29(3-4), 387-404.

Two solar flares of 25 July 1981 and 5 November 2004 of importance 2N and M4.1/1B, respectively, were investigated using observational data obtained with the Echelle spectrograph of the Kyiv University Astronomical Observatory. Stokes and V profiles of the FeI lines 5233, 5247.1, 5250.2, 5250.6, 5576.1 of CrI 5247.6 Angstrum have been analyzed. Several evidences found for the existence of spatially unresolved magnetic field structures with kG strengths. In particular, the values of the measured average longitudinal field B || depend on the Lande factors g of the lines: in general, B || increases with increasing factor g. Analogously, the observed line ratio B || (5250.2)/B || (5247.1) is increasing with increasing distance Δλ from the line center. The observed Stokes V profiles show some deviations from that of an assumed homogeneous field, presented by the Stokes I gradient, dI/dλ. A comparison with the non-split line FeI 5576.1 Angstrum shows that some of these deviations are real and indicate the presence of subtelescopic magnetic elements with discrete field strengths of several kG. The lines with large Lande factors have considerable broadenings of the Stokes/profiles, indicating a strong background magnetic field of mixed polarity. On the basis of all these data we conclude that a four-component magnetic field structure is a possible explanation. The field strengths are about ±1.05 kG in the background field, and 1.3-1.5, 3.9-4.0, and 7.4-7.8 kG at level of middle photosphere (h ~ 300 km) in the spatially unresolved, small-scale magnetic elements.

8 illus, 2 tables, 50 ref

018336   Krivova N A;Solanki S K (NO, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, Email: natalie@mps.mpg.de) : Moels of solar irradiance variations: current status. J Astrophys Astr 2008, 29(1-2), 151-8.

Regular monitoring of solar irradiance has been carried out since 1978 to show that solar total and spectral irradiance varies at different time scales. Whereas variations on time scales of minutes to hours are due to solar oscillations and granulation, variations on longer time scales are driven by the evolution of the solar surface magnetic field. Here the most recent advances in modelling of solar irradiance variations on time scales longer than a day are briefly reviewed.

5 illus, 50 ref

018335   Krishan V;Masuda S (NO, Indian Institute of Astrophysics, Bangalore-560 034, Email: vinod@iiap.res.in) : Magnetic transport on the solar atmosphere by turbulent ambipolar diffusion. Asian J Phys 2008, 17(3-4), 479-88.

The lower solar atmosphere consists of partially ionized turbulent plasmas harboring velocity field, magnetic field and current density fluctuations. The correlations amongst these small scale fluctuations give rise to large scale flows and magnetic fields which decisively affect all transport processes. The three fluid system consisting of electrons, ions and neutral particles supports nonideal effects such as the Hall effect and the ambipolar diffusion. Here, we study magnetic transport by ambipolar diffusion and compare the characteristic timescales of the laminar and the turbulent ambipolar diffusion processes. As expected from a turbulent transport process, the time scale of the turbulent ambipolar diffusion is found to be smaller by orders of magnitude as compared with the laminar ambipolar diffusion. The nonlinearity of the laminar ambipolar diffusion creates magnetic structures with sharp gradients which are amenable to processes such as magnetic reconnection and energy release there from for heating and flaring of the solar plasma.

15 ref

018334   Kohl J L;Jain R;Cranmer S R;Gardner L D; Pradhan A K;Raymond J C;Strachan L (NO, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA, Email: jkohl@cfa.harvard.edu) : Next generation UV coronagraph instrumentation for solar cycle-24. J Astrophys Astr 2008, 29(1-2), 321-7.

Ultraviolet coronagraph observations of the extended solar corona (definecfhere as 1.5 to 10 solar radii from Sun-center) have become a powerful tool for obtaining detailed empirical descriptions of coronal holes, streamers, and coronal mass ejections. The empirical models resulting from ultraviolet coronagraph observations provide the constraints needed to test and guide theoretical models aimed at determining the physical processes that control solar wind acceleration, CME heating and acceleration, and solar energetic particle (SEP) acceleration. Measurements to date from sounding rockets, the shuttle deployed Spartan 201 satellite and the Solar and Heliospheric Observatory (SOHO) have utilized high resolution spec-troscopy over a very limited instantaneous field of view. New concepts for next generation instrumentation include imaging ultraviolet spectro-coronagraphs and large aperture ultraviolet coronagraph spectrometers. An imaging instrument would be the first to obtain absolute spectral line intensities of the extended corona over a wide field of view. Such images would provide the absolute intensities of spectral lines that can be used to determine densities and outflow velocities of specific coronal ions. Measurements from several charge states of a given element will allow electron temperatures to be determined. These measurements combined with observations of H I Lya provide absolute chemical abundances (relative to hydrogen) for observed elements. Ultraviolet imaging would be highly complementary to a large-aperture ultraviolet coronagraph spectrometer designed for high spectral resolution observations over a small instantaneous field of view. The images would be used to select targets for more detailed spectroscopic studies with the large aperture UV coronagraph spectrometer and to provide time dependent empirical descriptions of the regions surrounding the narrow instantaneous field of view of the large aperture instrument. Descriptions of both the imaging ultraviolet spectro-coronagraph and the large aperture ultraviolet coronagraph spectrometer are provided. Recommended co-observing instruments are described.

5 illus, 5 ref

018333   Karthikeyan B;Rajamanickam N;Bagare S P (NO, Physics Research Centre, VHNSN College, Virudhunagar-626 001, Email: nrmanickam@rediffmail.com) : Evaluation of astrophysically useful parameters for certain band systems of BBr, BC1 and BD molecules. Asian J Spectrosc 2008, 12(4), 157-61.

For the estimation of physical conditions of the astrophysical sources, it is desirable to have knowledge of molecular parameters like dissociation energies, potential energy curves data, Franck-Condon (FC) factors and r-centroids, etc. In consideration of such astrophysical applications, the transition probability parameters like FC factors and r-centroids for the band systems A ^{1Π - X 1Σ, a 3Π₀₊ - X 1Σ of BBr; A - X, a - X of BC1 and A - X, B - X of BD molecule have been evaluated using a suitable potential function. The evaluated FC factors and r-centroids have also been compared with the already reported values for some band systems. Their physical and astrophysical interpretations have/been discussed.}

6 tables, 23 ref

018332   Kariyappa R (NO, Indian Institute of Astrophysics, Bangalore-560 034, Email: rkari@iiap.res.in) : Spatially resolved images and solar irradiance variability. J Astrophys Astr 2008, 29(1-2), 159-62.

The Sun is the primary source of energy that governs both the terrestrial climate and near-earth space environment. Variations in UV irradiances seen at earth are the sum of global (solar dynamo) to regional (active region, plage, network, bright points and background) solar magnetic activities that can be identified through spatially resolved photo-spheric, chromospheric and coronal features. In this research, the images of Call K-line (NSO/Sac Peak) have been analysed to segregate the various chromospheric features. We derived the different indices and estimated their contribution from the time series data to total Call K emission flux and UV irradiance variability. A part of the important results from this research is discussed in this paper.

1 illus, 10 ref

018331   Kamath U S;Ashok N M;Anupama G C (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034, Email: uskamath@iiap.res.in) : Nova V4444 Sagittarii 1999 in the early decline and quiescent phases. Bull Astr Soc India 2008, 36(4), 141-50.

Presents near-infrared and optical spectra of the fast nova V4444 Sagittarii at two single epochs in the early decline phase and unfiltered images obtained in quiescence. Based on this and other available data, we discuss about the nature of this nova, including the possibility of it being a recurrent nova.

5 illus, 2 tables, 13 ref

018330   Kalkofen W (NO, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA, Email: wolf@cfa.harvard.edu) : Wave heating of the solar chromosphere. J Astrophys Astr 2008, 29(1-2), 163-6.

The nonmagnetic interior of supergranulation cells has been thought since the 1940s to be heated by the dissipation of acoustic waves. But all attempts to measure the acoustic flux have failed to show sufficient energy for chromospheric heating. Recent space observations with TRACE, for example, have found 10% or less of the necessary flux. To explain the missing energy it has been speculated that the nonmagnetic chromosphere is heated mainly by waves related to the magnetic field. If that were correct, the whole chromosphere, magnetic as well as nonmagnetic, would be heated mainly by waves related to the magnetic field. But contrary to expectation, the radiation emerging from the nonmagnetic chromosphere shows none of the signatures of magnetic waves, only those of acoustic waves. Nearly all the heating of the nonmagnetic chromosphere must therefore be due to acoustic waves. In the magnetic network on the boundary of supergranulation cells, on the other hand, the small filling factor of the magnetic field in the photosphere implies that only a small fraction of the wave flux that travels upward to heat the chromosphere can be channeled by the magnetic field. Hence, while some of the energy that is dissipated in the magnetic network is in the form of magnetic waves, most of it must be in the form of acoustic waves. Thus, the quiet solar chromosphere, instead of being heated mainly by magnetic waves throughout, must be heated mainly by acoustic waves throughout. The full wave flux heating the quiet chromosphere must travel through the photosphere. In the nonmagnetic medium, this flux is essentially all in the form of acoustic waves; TRACE registers at most 10% of it, perhaps because of limited spatial resolution.

15 ref

018329   Jain R;Bharti L (Physical Research Laboratory, , Navrangpura, Ahmedabad-380 009, Email: rajmal@prl.res.in) : Genesis of solar flares and associated phenomena. Asian J Phys 2008, 17(3-4), 319-45.

Discusses concept of the solar flare and associated phenomena. Began with very small-scale solar flare activity such as umbral dots occurring inside the sunspot's umbra. Presents recent evidences for the umbral dots to be the result of magnetoconvection in the photosphere. Also discusses recent discoveries in contrast to previous studies of light-bridges, and their context to flare associated phenomena. The opposite polarity of the light-bridge with respect to its parent sunspot was demonstrated and thereby how low-altitude reconnection causes mass ejection associated with flare/Ellerman bembs is proposed. Defines elaborately the concept of the flare in general and "confined" and "eruptive" classes of flares in particular. The various flare associated phenomena such as surges, spray and veil emission, flare loops have been reviewed with current status on these topics. These subjects have been changing with revolution in observational capabilities. In last two decades YOHKOH, SOHO, TRACE, RHESS1 and SOXS, arid more recently Hinode missions have changed the earlier concepts significantly, which have, however, enabled us to improve our understanding of this phenomenon on one side, as well as to improve our theories on the other side. The particle acceleration has been reviewed considering as a focal theme subject. The subject of microflares and nanoflares has been always a center of attraction among solar physicists since Parker [1] proposed them as potential candidates for coronal heating, which, however, does not convincingly appear the case, and made full efforts to describe this phenomena in greater detail.

13 illus, 158 ref

018328   Jain R;Aggarwal M;Sharma R (Physical Research Laboratory, Space Dep, , Government of India, Navrangpura, Ahmedabad-380 009) : X-ray emission from solar flares. J Astrophys Astr 2008, 29(1-2), 125-45.

Solar X-ray Spectrometer (SOXS), the first space-borne solar astronomy experiment of India was designed to improve our current understanding of X-ray emission from the Sun in general and solar flares in particular. SOXS mission is composed of two solid state detectors, viz., Si and CZT semiconductors capable of observing the full disk Sun in X-ray energy range of 4-56 keV. The X-ray spectra of solar flares obtained by the Si detector in the 4-25 keV range show evidence of Fe and Fe/Ni line emission and multi-thermal plasma. The evolution of the break energy point that separates the thermal and non-thermal processes reveals increase with increasing flare plasma temperature. Small scale flare activities observed by both the detectors are found to be suitable to heat the active region corona; however their location appears to be in the transition region.

14 illus, 20 ref

018327   Jain R (NO, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009, Email: rajmal@prl.res.in) : X-ray spectroscopy of solar flares. Asian J Phys 2008, 17(3-4), 509-32.

Review firstly describes the X-ray emission from the solar flares and the focal science aspects that require the X-ray spectroscopy to improve understanding of the solar flares. Presents briefly the X-ray spectroscopy carried out with scintillation detectors mounted onboard SMM and YOHKOH in last century, and, therewith next generation solid state detectors onboard RHESSI and SOXS missions in this decade. Considered the X-ray high resolution spectroscopy as important diagnostic tool to understand the solar flares mechanism, and therefore we present in particular the instrumentation details, and results from Si and CZT detectors of SOXS mission in this article, which may enable youngsters to plan next generation space-borne experiments with superb resolution using advance technology.

14 illus, 1 table, 52 ref

018326   Jadeja A L;Iyer K N;Vats H O;Manoharan P K (NO, Christ College, Saurashtra Univ, Rajkot-360 005) : Geo-effectiveness of CMEs. J Astrophys Astr 2008, 29(1-2), 287-91.

Coronal Mass Ejections (CMEs) are important phenomena in coronal dynamics causing interplanetary signatures (ICMEs). They eject large amounts of mass and magnetic fields into the heliosphere, causing major geomagnetic storms and interplanetary shocks. Geomagnetic storms are often characterized by abrupt increases in the northward component of the earth's field, called sudden commencements (SSC) followed by large decreases of the magnetic field and slow recovery to normal values. The SSCs are well correlated with IP shocks. Here a case study of 10-15 February 2000 and also the statistical study of CME events observed by IPS array, Rajkot, during the years 2000 to 2003 and Radio Astronomy Center, Ooty are described. The geomagnetic storm index Dst, which is a measure of geo-effectiveness, is shown to be well correlated with normalized scintillation index 'g', derived from Ooty Radio Telescope (ORT) observations.

3 illus, 13 ref

018325   Hollweg J V (Space Science Center, Morse Hall, University of New Hampshire, Durham, Email: joe.hollweg@ung.edu) : Solar wind: our current understanding and how we got here. J Astrophys Astr 2008, 29(1-2), 217-37.

In the original theory for the solar wind, the electron pressure gradient was the principal accelerating force. This was soon recognized to be insufficient to drive the high-speed streams. Subsequently, the discovery of Alfven waves in the solar wind led to a long series of models in which wave pressure provided additional acceleration, but these wave-driven models ultimately failed to explain the rapid acceleration of the fast wind close to the Sun. An alternate view was that the pressure of hot protons close to the Sun could explain the rapid acceleration, with the proton heating coming from the cyclotron resonance. SOHO has provided remarkable data which have verified some of the predictions of this view, and given impetus to ongoing studies of the ion-cyclotron resonance in the fast wind. After a historical review, we discuss the basic ideas behind current research, emphasizing the importance of particle kinetics. We conclude with some guesses as to how work might proceed in the future.

4 illus, 150 ref

018324   Harra L K (NO, , UCL-Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK, Email: lkh@mssl.ucl.ac.uk) : Solar flares and associated phenomena. Asian J Phys 2008, 17(3-4), 363-82.

A solar flare was first observed in 1859, and since that time scientists have been driven to understand and ultimately predict the most energetic phenomena in the solar system. Flares usually occur in regions with strong magnetic fields located in sunspots, and generally speaking this follows an activity cycle of approximately 11 years. Flares are often related to coronal mass ejections and have an impact on the space weather that surrounds the planets. Describes the latest understanding on solar flares derived through new simulations and from observations from a wide range of space missions including TRACE, SOHO, RHESSI and the recently launched Hinode and STEREO missions.

15 illus, 100 ref

018323   Gurugubelli U K;Sahu D K;Anupama G C; Chakradhari N K (Joint Astronomy Programme, Indian Institute of Science, Bangalore) : Photometric and spectroscopic evolution of type II-P supernova SN 2004A. Bull Astr Soc India 2008, 36(2-3), 79-97.

Presents optical photometry and spectroscopy of the normal type IIP supernova SN2004A, which was discovered in the galaxy NGC 6207 on 2004 January 9.84UT. Early observations indicated that the supernova was discovered at about two weeks since explosion. Estimates the distance to NGC 6207 to be 20.35±4.5 Mpc using the Standard Candle method. Using this distance, estimate the ejected nickel mass in the explosion to be 0.032±0.02 M. The plateau luminosity, its duration (about 80 days) and the expansion velocity of the supernova ejecta at the middle of the plateau indicate an explosion energy of 4.7 ± 2.7 x 10⁵⁰ ergs and an ejected envelope mass of 7.2± 2.2 M. The ejected envelope mass implies a main sequence mass of 10±2.5 M for the progenitor.

9 illus, 5 tables, 36 ref

018322   Gupta M;Jain R;Trivedi J;Mishra A P (Physics Dep, A.P.S. Univ, Rewa-486 003, Email: soumya_rishi@rediffmail.com) : Microflares as possible sources for coronal heating. J Astrophys Astr 2008, 29(1-2), 171-7.

Presents preliminary study of 27 microflares observed by Solar X-ray Spectrometer (SOXS) mission during July 2003 to August 2006. Founds that all 27 microflares show the Fe-line feature peaking around 6.7 keV, which is an indicator of the presence of coronal plasma temperature ≥ 9 MK. On the other hand, the spectra of microflares show hybrid model of thermal and non-thermal emission, which further supports them as possible sources of coronal heating. The results based on the analysis show that the energy relapsed by the microflares is good enough for heating of the active corona. Discusses the results in the light of the hybrid model of microflares production.

3 illus, 1 table, 12 ref

018321   Gosain S;Tiwari S;Joshi J;Venkatakrishnan P (Udaipur Solar Observatory, Physical Research Laboratory, , P.O. Box 198, Udaipur-313 001, Email: sgosain@prl.res.in) : Software for interactively visualizing solar vector magnetograms of Udaipur solar observatory. J Astrophys Astr 2008, 29(1-2), 107-111.

The Solar Vector Magnetograph (SVM) at Udaipur Solar Observatory saw its first light in April 2005. The retrieval of vector fields from the imaging spectro-polarimetric observational data requires a substantial amount of computer post-processing. The GUI-based data reduc-tion and analysis software have been developed to make the data processing pipeline user-friendly and less time-consuming. In this paper we describe these software packages.

3 illus, 5 ref

018320   Frank Hill (National Solar Observatory, , Tucson, Arizona 85719, USA, Email: fhill@noao.edu) : Helioseismology and the solar cycle: past, present and future. J Astrophys Astr 2008, 29(1-2), 75-84.

A major goal of helioseismology is to understand the mechanism of the solar cycle. In this paper, some results of helioseismic observations relevant to the cycle are briefly reviewed, the current state-of-the-art is discussed, and near-term future directions are sketched out. Topics covered include the internal rotation rate; activity-related parameter variations; the tachocline; far-side imaging; the torsional oscillation; and meridional flows.

8 illus, 33 ref

018319   Dikpati M;Gilman P A (High Altitude Observatory, NCAR, 3080 Center Green, Boulder CO 80301, USA, Email: dikpati@hao.ucar.edu) : Global solar dynamo models: simulations and predictions. J Astrophys Astr 2008, 29(1-2), 29-39.

Flux-transport type solar dynamos have achieved considerable success in correctly simulating many solar cycle features, and are now being used for prediction of solar cycle timing and amplitude. First defines flux-transport dynamos and demonstrate how they work. The essential added ingredient in this class of models is meridional circulation, which governs the dynamo period and also plays a crucial role in determining the Sun's memory about its past magnetic fields. It has been shows that flux-transport dynamo models can explain many key features of solar cycles. Shows that a predictive tool can be built from this class of dynamo that can be used to predict mean solar cycle features by assimilating magnetic field data from previous cycles.

5 illus, 28 ref

018318   Devi B;Dubey S;Saini S;Rajini Devi;Wahi R; Dhar A;Vijay S K;Gwal A K (Space Science Laboratory, Physics Dep, Barkatullah Univ, Bhopal-462 026) : Geomagnetic field variation during winter storm at localized southern and northern high latitude. J Astrophys Astr 2008, 29(1-2), 275-80.

This paper presents the effect of geomagnetic storm on geomagnetic field components at Southern (Maitri) and Northern (Kiruna) Hemispheres. The Indian Antarctic Station Maitri is located at geom. long. 66.03° S; 53.21° E whereas Kiruna is located at geom. long. 67.52° N; 23.38° E. We have studied all the geomagnetic storms that occurred during winter season of the year 2004-2005. We observed that at Southern Hemisphere the variation is large as compared to the Northern Hemisphere. Geomagnetic field components vary when the interplanetary magnetic field is oriented in southward direction. Geomagnetic field components vary in the main phase of the ring current. Due to southward orientation of vertical component of IMF reconnection takes place all across the dayside that transports plasma and magnetic flux which create the geomagnetic field variation.

1 illus, 6 ref

018317   Debnath D;Chakrabarti S K;Nandi N;Mandal S (NO, Indian Centre for Space Physics, Chalantika 43, Garia Station, Kolkata-700 084, Email: dipak@csp.res.in) : Spectral and timing evolution of GRO J1655-40 during its outbrust of 2005. Bull Astr Soc India 2008, 36(4), 151-89.

In a recent outburst which lasted for 260 days, the black hole candidate GRO J1655-40 exhibited a behaviour similar to its last; outburst observed almost eight years ago. Analyzes a total of 150 observational spells in 122 days of data spreaded over the entire outburst phase of Feb. 2005 to Oct. 2005. From study, a comprehensive understanding of the detailed behaviour of this black hole candidate has emerged. Based on the degree of importance of the black body and the power-law components we divide the entire episode in four spectral states, namely, hard, soft, very soft and intermediate. Quasi-Periodic oscillations (QPOs) were found in two out of these four states, namely, in the hard and the intermediate states. In the hard state, at the rising phase of the outburst, QPO frequency ranged from 0.034 - 17.78Hz and the spectra was fitted by a disk black body, power-law and iron emission line at 6.2 - 6.5 keV. In the intermediate state, QPOs vary from IS.lTHz to 19 04Hz and the QPO frequency modulation in this state was not significant. The spectra in this state are well fitted by the disk black body and the power-law components. In the hard state of the declining phase of the outburst, we found QPOs of decreasing frequency from 13.14 Hz to 0.034 Hz. The spectra of this state were fitted by a disk black body and power-law components, but in the initial few days a cooler Comptonized component was required for a better fit. In the soft/very soft states, the spectral states are mostly dominated by the strong disk black body component.

11 illus, 5 tables, 39 ref

018316   Dasgupta A;Laming J M (NO, , Naval Research Laboratory, Washington DC 20375, Email: arati.dasgupta@nrl.navy.mil) : Analysis of ion charge states in solar wind and CMEs. J Astrophys Astr 2008, 29(1-2), 211-15.

Discusses needs in dielectronic recombination data motivated by recent work directed at a quantitative understanding of ion charge states of various elements observed in situ in the solar wind and CMEs. The competing processes of ionization and recombination lead to departures from collision ionization equilibrium. The use of this as a diagnostic of acceleration and heating processes of the solar wind and CMEs is sensitive to the accuracy of the atomic rates in a way that steady state ionization equilibrium plasmas are not. The most pressing need is dielectronic recombination rates for ions Fe8+-12+. These are among the dominant species observed in various regions of the solar wind and CMEs, and in remotely sensed EUV spectra.

2 illus, 11 ref

018315   Choudhuri A R (Physics Dep, Indian Institute of Science, Bangalore-560 012, Email: arnab@physics.iisc.ernet.in) : Prospects for predicting cycle 24. J Astrophys Astr 2008, 29(1-2), 41-7.

Although authors have reliable data of solar polar fields only from the mid-1970s, it seems that the polar field at a minimum is well correlated with the next cycle, but the strength of the cycle is not correlated with the polar field produced at its end. Explains this by suggesting that the Babcock-Leighton mechanism of poloidal field generation from tilted active regions involves randomness, whereas the other aspects of the dynamo process are more ordered. To model actual cycles, we have to 'correct' our theoretical dynamo model by 'feeding' information about the polar field at the minima. Following this process, we find that our model fits the observed sunspot numbers of cycles 21-23 reasonably well and predicts that cycle 24 will be the weakest in a century.

3 illus, 15 ref

018314   Chen P F (Astronomy Dep, Nanjing Univ, Nanjing-210 093, China, Email: chenpf@nju.edu.cn) : Initiation and propagation of coronal mass ejections. J Astrophys Astr 2008, 29(1-2), 179-86.

Reviews recent progress in the research on the initiation and propagation of CMEs. In the initiation part, several trigger mechanisms are discussed; in the propagation part, the observations and modelings of BIT waves/dimmings, as the EUV counterparts of CMEs, are described.

1 illus, 50 ref

018313   Chandrasekhar Reddy A;Rathod J;Rajaram G; Alyana R;Misra D S;Patil C G;Prasad M Y S;Ananth A G (CSRE, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076) : Energy dependence of near-relativistic electron spectrum at geostationary orbit during the SEP events of 2005. J Astrophys Astr 2008, 29(1-2), 313-17.

In view of the renewed interest in the study of energetic particles in the outer radiation belt of the earth, we feel it will be helpful in looking for the energy dependence of the electron energy spectrum at geostationary orbit. This may give us some insight into how we can safeguard geostationary satellites from functional anomalies of the deep dielectric charging type, which are caused by charge accumulation and subsequent discharge of relativistic electrons. In this study we examine whether there is any energy dependence in relativistic electron enhancements at geosynchronous altitudes during solar energetic proton events of 2005.

2 illus, 10 ref

018312   Chandra H;Vats H O;Sharma S (NO, Physical Research Laboratory, Ahmedabad-380 009, Email: hchandra@prl.res.in) : Effect of solar flares on the interplanetary medium and terrestrial environment. Asian J Phys 2008, 17(3-4), 489-508.

There are several energetic phenomena that take place on the Sun and these have tremendous effect on the entire heliosphere including our planet Earth. Solar flares are one of the most energetic events in the whole solar system. The effects of solar flares are very complex on the interplanetary medium and terrestrial environment. There are direct and indirect effects on our environment. Some of these are almost instantaneous, whereas others are delayed. Study reviews many of these effects both on statistical basis as well as on a few case studies.

12 illus, 89 ref

018311   Callebaut D K;Makarova V V (Physics Dep, GGB, Antwerp Univ, B-2020 Antwerp, Belgium) : Prediction of peaks in wolf numbers in cycle 24 according to actual numbers of polar faculae. J Astrophys Astr 2008, 29(1-2), 69-73.

Previous investigations by Makarov et al. have shown a relation between the peaks in the number of polar faculae and the peaks in the Wolf number. In cycles 20 and 22 the delay between peaks in polar faculae and Wolf number was 6.1 ± 0.1 year, north and south taken separately, as their peaks do not coincide. For the odd cycle 21, this shift was 5.6 years average. Polar faculae always precede the sunspots. The relevance of this for the dynamo mechanism is obvious. In cycle 23 the delay was 7.7 year (north) and 7.8 year (south). The approach of a deep minimum is probably responsible for this increased delay; thus for cycle 24 the delay between peaks of polar faculae and sunspots is expected to be at least 7.8 years and probably longer. The present polar faculae show 6 peaks above the smoothed average (north) and similarly 3 peaks south. The first peak for the sunspots will be at the earliest during the very end of 2007. As soon as one peak in the spots occurs the delay for cycle 24 can be estimated and the other peaks predicted.

2 illus, 14 ref

018310   Bhattacharya S;Dubey S;Tiwari R;Purohit P K; Gwal A K (Space Science Laboratory, Physics Dep, Barkatullah Univ, Bhopal-462 026) : Effect of magnetic activity on ionospheric time delay at low latitude. J Astrophys Astr 2008, 29(1-2), 269-74.

The purpose of this work is to investigate the effect of magnetic activity on ionospheric time delay at low latitude Station Bhopal (geom. lat. 23.2°N, geom. long. 77.6°E) using dual frequency (1575.42 and 1227.60 MHz) GPS measurements. Data from GSV4004A GPS Ionospheric Scintillation and TEC monitor (GISTM) have been chosen to study these effects. Presents the results of ionospheric time delay during quiet and disturbed days for the year 2005. Results show that maximum delay is observed during quiet days in equinoxial month while the delays of disturbed period are observed during the months of winter. Also studied the ionospheric time delay during magnetic storm conditions for the same period. Results do not show any clear relationship either with the magnitude of the geomagnetic storm or with the main phase onset (MPO) of the storm. But most of the maximum ionospheric time delay variations are observed before the main phase onset (MPO) or sudden storm commencement (SSC) as compared to storm days.

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018309   Bayanna A R;Kumar B;Louis R E;Venkatakrishnan P;Mathew S K (Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Dewali, Badi Road, Udaipur-313 001, Email: bayanna@prl.res.in) : Development of a low-order adaptive optics system at Udaipur solar observatory. J Astrophys Astr 2008, 29(1-2), 353-7.

A low-order Adaptive Optics (AO) system is being developed at the Udaipur Solar Observatory and we present in this paper the status of the project, which includes the image stabilization system and calibration of wavefront sensor and deformable mirror. The image stabilization system comprises of a piezo driven tip-tilt mirror, a high speed camera (955 fps), a frame grabber system for sensing the overall tilt and a Linux based Intel Pentium 4 control computer with Red Hat Linux OS. The system operates under PID control. In the closed loop, an rms image motion of 0.1-0.2 arcsec was observed with the improvement factor varying from 10-20 depending on the external conditions. Error rejection bandwidth of the system at OdB is 80-100 Hz. In addition to that, we report the on-going efforts in the calibration of lenslet array and deformable mirror for sensing and correcting the local tilt of the wavefront.

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018308   Aschwanden M J (NO, Lockheed Martin Advanced Technology Center, Solar and Astropysics Labo, Bldg. 252, Org, ADBS, 3251 Hanover St., Palo Alto, CA 94204, USA, Email: aschwanden@lmsal.com) : Solar flare physics enlivened by TRACE and RHESSI. J Astrophys Astr 2008, 29(1-2), 115-24.

The Transition Region and Coronal Explorer (TRACE) gave us the highest EUV spatial resolution and the Ramaty High Energy Solar Spec-trometric Imager (RHESSI) gave us the highest hard X-ray and gamma-ray spectral resolution to study solar flares. We review a number of recent highlights obtained from both missions that either enhance or challenge our physical understanding of solar flares, such as: 1. Multi-thermal Diagnostic of 6.7 and 8.0 keV Fe and Ni lines, 2. Multi-thermal Conduction Cooling Delays, 3. Chromospheric Altitude of Hard X-Ray Emission, 4. Evidence for Dipolar Reconnection Current Sheets, 5. Footpoint Motion and Reconnection Rate, 6. Evidence for Tripolar Magnetic Reconnection, 7. Displaced Electron and Ion Acceleration Sources.

6 illus, 19 ref

018307   Aschwanden M J (NO, Lockheed Martin Advanced Technology Center, Solar and Astrophysics Lab, Bldg.252, Org. ADBS, 3251 HanoverSt., Palo Alto, CA 94304, USA, Email: aschwanden@imsal.com) : New aspects on particle acceleration in solar flares from RHESSI observations. Asian J Phys 2008, 17(3-4), 423-44.

Review highlights a number of recent RHESSI observations that are directly relevant to the study of particle acceleration processes in solar flares. Many observations confirm our basic standard models of acceleration in various types of coronal magnetic reconnection regions, but reveal a number of unexpected features that either require more detailed magnetic, hydrodynamic, and kinetic modeling or rethinking in terms of alternative models.

15 illus, 1 table, 67 ref

018306   Antia H M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005, Email: antia@tifr.res.in) : Seismic study of magnetic field in the solar interior. J Astrophys Astr 2008, 29(1-2), 85-92.

Magnetic field in the solar interior contributes to the even order splitting coefficients, but it is not possible to separate the effect of magnetic field from those due to other deviations from spherical symmetry. Results obtained using GONG and MDI data are discussed. Limits on possible magnetic field in the solar core and in the tachocline region are obtained. There is some signal from possible magnetic field in the convection zone, but evidence of possible temporal variation in the solar interior is only marginal.

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018305   Ansari I A (Physics Dep, Aligarh Muslim Univ, Aligarh-202 002, Email: iaaamuphysics@gmail.com) : Multipoint observations of low latitude ULF Pc3 waves in south-easter Australia. J Astrophys Astr 2008, 29(1-2), 303-11.

Geomagnetic pulsations recorded on the ground are the signatures of the integrated signals from the magnetosphere. Pc3 geomagnetic pulsations are quasi-sinusoidal variations in the earth's magnetic field in the period range 10-45 seconds. The magnitude of these pulsations ranges from fraction of a nT (nano Tesla) to several nT. These pulsations can be observed in a number of ways. However, the application of ground-based magnetometer arrays has proven to be one of the most successful methods of studying the spatial structure of hydromagnetic waves in the earth's magnetosphere. The solar wind provides the energy for the earth's magne-tospheric processes. Pc3-5 geomagnetic pulsations can be generated either externally or internally with respect to the magnetosphere. The Pc3 studies undertaken in the past have been confined to middle and high latitudes. The spatial and temporal variations observed in Pc3 occurrence are of vital importance because they provide evidence which can be directly related to wave generation mechanisms both inside and external to the magnetosphere. At low latitudes (L < 3) wave energy predominates in the Pc3 band and the spatial characteristics of these pulsations have received little attention in the past. An array of four low latitude induction coil magnetometers were established in south-east Australia over a longitudinal range of 17 degrees at L = 1.8 to 2.7 for carrying out the study of the effect of the solar wind velocity on these pulsations. Digital dynamic spectra showing Pc3 pulsation activity over a period of about six months have been used to evaluate Pc3 pulsation occurrence. Pc3 occurrence probability at low latitudes has been found to be dominant for the solar wind velocity in the range 400-700 km/s. The results suggest that solar wind controls Pc3 occurrence through a mechanism in which Pc3 wave energy is convected through the magnetosheath and coupled to the standing oscillations of magnetospheric field lines.

5 illus, 3 tables, 25 ref

018304   Ambastha A (Udaipur Solar Observatory, Physical Research Laboratory, , Udaipur-313 001, Email: ambastha@prl.ernet.in) : Helioseismic effects of energetic transients. J Astrophys Astr 2008, 29(1-2), 93-101.

Photospheric and chromospheric signatures related to large, energetic transients such as flares and CMEs, have been extensively reported during the last several years. In addition, energetic solar transients are expected to cause helioseismic effects. Some of the recent results are reviewed here; in particular, the helioseismic effects of the powerful flares in superactive region, NOAA 10486, including the 4B/X17 superflare of October 28, 2003. We also examine the temporal variations of power in low-l modes during the period May 1995-October 2005, and compare with daily, disk-integrated flare- and CME-indices to infer the effect of transients on the scale of whole solar disk.

6 illus, 33 ref

018303   Aggarwal M;Jain R;Mishra A P;Kulkarni P G; Vyas C;Sharma R;Gupta M (NO, Physical Rersearch Laboratory, Navrangpura, Ahmedabad-380 009) : X-ray emission characteristics of flares associated with CMEs. J Astrophys Astr 2008, 29(1-2), 195-205.

Present the study of 20 solar flares observed by "Solar X-ray Spectrometer (SOXS)" mission during November 2003 to December 2006 and found associated with coronal mass ejections (CMEs) seen by LASCO/SOHO mission. In this investigation, X-ray emission characteristics of solar flares and their relationship with the dynamics of CMEs have been presented. We found that the fast moving CMEs, i.e., positive acceleration are better associated with short rise time (< 150 s) flares. However, the velocity of CMEs increases as a function of duration of the flares in both 4.1-10 and 10-20 keV bands. This indicates that the possibility of association of CMEs with larger speeds exists with long duration flare events. We observed that CMEs decelerate with increasing rise time, decay time and duration of the associated X-ray flares. A total 10 out of 20 CMEs under current investigation showed positive acceleration, and 5 of them whose speed did not exceed 589 km/s were associated with short rise time (< 150s) and short duration (< 1300s) flares. The other 5 CMEs were associated with long duration or large rise time flare events. The unusual feature of all these positive accelerating CMEs was their low linear speed ranging between 176 and 775 km/s. We do not find any significant correlation between X-ray peak intensity of the flares with linear speed as well as acceleration of the associated CMEs. Based on the onset time of flares and associated CMEs within the observing cadence of CMEs by LASCO, we found that in 16 cases CME preceded the flare by 23 to 1786 s, while in 4 cases flare occurred before the CME by 47 to 685 s. We argue that both events are closely associated with each other and are integral parts of one energy release system.

6 illus, 1 table, 27 ref

017326   Sankaran A V (NO, , No.10, P and T Colony, Ist, Cross, II Block, R.T. Nagar, Bangalore-560 032, Email: av.sankaran@gmail.com) : Galactic triggering of geologic events in earth's history. Curr Sci 2008, 95(6), 714-16.

1 illus, 15 ref

010976   Rastogi R G;Chandra H (NO, Physical Research Laboratory, Ahmedabad-380 009) : Space disturbance effect on equatorial sporadic-E during sunrise. Indian J Radio Space Phys 2009, 38(2), 105-11.

The space weather event of 25 September 1998 and its effect in the E-region near magnetic equator has been studied. The geomagnetic H field variations recorded at low latitudes was normal on 24 and 26 September 1998 but there was a geomagnetic storm on 25 September with sudden commencement at 0445 hrs LT (75° EMT). There was a strong counter electrojet after sunrise associated with the magnetic storm. Solar wind speed and ion density and the interplanetary magnetic field (IMF) data show the IMF BZ turning towards south in the morning on 25 September 1998 and solar wind velocity was 850 kms^-1. Quarter hourly ionograms at Thumba, located close to the dip equator were examined during morning hours on 24-26 September 1998. On 24 and 26 September 1998, E-region irregularities (E_s-q) were first generated about an hour after the appearance of fresh E-region ionization following sunrise and by the time ΔH at Trivandrum started increasing above the corresponding value at Alibag. On the disturbed day, 25 September 1998, E_s-q appeared later due to occurrence of counter electrojet after sunrise. This is caused by electric field changes associated with the magnetic storm rather than the late reversal of the electric field in the morning.

006090   Sunil Krishna M V;Vir Singh (Physics Dep, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: virphfph@iitr.ernet.in) : Testing of Solar2000 EUV flux model in 900-1350 Å wavelength range using greenline dayglow emission. Indian J Radio Space Phys 2009, 38(1), 37-41.

The contribution of photodissociation of molecular oxygen to the total volume emission rate of greenline dayglow emission at 5577 Å is modelled in the study. The Solar EUV radiation fluxes for modelling are obtained from the Solar2000 V 2.25 model. The modelling has been done in the altitude range 92-105 km, where photodissociation and three body recombination are main contributing processes to greenline dayglow emission. The present results are discussed in the light of Wind Imaging Interferometer (WINDII) observations of greenline dayglow emission in the altitude range 92-105 km. It is found that the Solar2000 V2.25 flux model gives better agreement with the WINDII observations especially in the range 92-96 km where earlier models predicted a very low emission rate. In the mesospheric emission peak region, present results are higher than the measurements and this discrepancy may possibly be attributed to higher values of solar fluxes for those spectral lines which are main sources of production of greenline dayglow emission. The present study suggests the re-examination of Solar2000 flux model at least for those spectral lines which are the main sources of greenline dayglow emission in mesospheric emission peak region.

006089   Shukla A K;Shinghal P;Sivaraman M R; Bandyopadhyay K (NO, SATCOM & IT Applications Area, Space Applications Centre, ISRO, Ahmedabad-380015, Email: ashishs@sac.isro.gov.in) : Comparative analysis of the effect of ionospheric delay on user position accuracy using single and dual frequency GPS receivers over Indian region. Indian J Radio Space Phys 2009, 38(1), 57-61.

The ionosphere acts as a prominent source of range errors for users of Global Positioning System (GPS) satellite signals requiring accurate position determination. Various models and mathematical formulations have been devised to calculate the absolute range error caused due to ionospheric delay. The present study aims at comparing two methods for calculating delay due to ionosphere: (i) using grid based model at L1 carrier frequency with bilinear interpolation technique; and (ii) using pseudo-range measurements at both L1 and L2 carrier frequency. For analyzing the effect of ionospheric delay on the seasonal behaviour of positional accuracy, a quantitative analysis has been done for all quiet days (Ap index < 50) in 2005 using GPS data for International GNSS Service (IGS) Bangalore (IISc) receiver in January, March and June. Various corrections such as satellite clock bias, transit time, ionospheric delay corrections, etc. are applied to pseudo-ranges to calculate the user coordinates. For single frequency (L1) receivers, ionospheric delay corrections have been applied using IGS total electron content data derived from grid based ionospheric model; and for the dual frequency receivers, pseudo-range measurements at L1 and L2 carrier frequencies have been used. It has been observed that there is an improvement of 1-4 m in the standard deviation of position errors when the ionospheric delay correction is applied using pseudo-range measurements at L1 and L2 frequencies (dual frequency receiver) as compared to L1 frequency only. It has also been observed that some residual errors still remain in the estimated user position even after using dual frequency receivers.

006088   Pan C J;Brahmanandam P S (Institute of Space Science, National Central University, Chung-Li 32054, Taiwan, R.O.C, Email: cjpan@jupiter.ss.ncu.edu.tw) : Range rate variation studies of the low-altitude quasi-periodic radar echoes during SEEK-2 campaign. Indian J Radio Space Phys 2009, 38(1), 50-6.

The first experimental evidence on range rate reversal of lowaltitude quasi-periodic (LQP) echoes from nighttime midlatitude sporadic E region with systematic characteristics in their occurrences for the echoes observed during SEEK- 2 (Sporadic-E Experiment over Kyushu) campaign with 24.515 MHz frequency agile radar located at Tanegashima in southern Japan (30.75°N, 130.03°E, geomagnetic latitude 20.97°N, dip angle 43.2°N) is presented. Four reversal cases of LQP echoes are found during the observation period. The reversal times of these echoes from positive QP to negative QP are found between 2000 and 2400 hrs LT and negative QP to positive QP around 0200 hrs LT. Besides, Doppler velocities associated with these echoes show preferential directions meaning that they are consistent with the sign of range rate of QP echoes in most cases. As the backscatter echoes studied are confined to the collision dominated lower E region and semi-diurnal tide is most pronounced at latitude higher than 30°, large-period neutral winds such as tidal and planetary waves in addition to atmospheric gravity waves play a role in the generation and control of these backscatter echoes.

006087   Kazimirovsky E S;Vergasova G V (NO, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences (, Post Box 4026, 664033, Irkutsk, Russia, Email: ekazimirovsky@yandex.ru) : Mesospheric, lower thermospheric dynamics and external forcing effects: a review. Indian J Radio Space Phys 2009, 38(1), 7-36.

Presents some of the most important experimental results and models obtained by international scientific community during last decade for the mesospheric and lower thermospheric dynamics (mean winds, planetary waves, tides and internal gravity waves). In addition to climatological features, the external forcing - the coupling from below (stratosphere) and possible influence of solar and geomagnetic activity on the dynamical processes at this region are presented.

006086   Brahmanandam P S;Pan C J;Lee C C;Tsai W C (Institute of Space Science, National Central University, Chung- Li 32054, Taiwan, Email: cjpan@jupiter.ss.ncu.edu.tw) : E-region irregularity observed by the Tanegashima Frequency Agile Radar during SEEK-2 campaign. Indian J Radio Space Phys 2009, 38(1), 42-9.

Reports the nighttime field-aligned plasma irregularity (FAI) at 6.1 m in E-region during SEEK-2 (Sporadic E Experiment over Kyushu) campaign during July-August 2002 using Tanegashima (30.75°N, 131.03°E, geomagnetic 20.97°N, dip 43.2°N) Frequency Agile Radar (FAR) operated at 24.515 MHz. According to the characteristics of radar echo, the echoes are classified into four types: negative quasi-periodic (NQP) echo; positive quasi-periodic (PQP) echo; continuous echo; and undefined echo. A study shows that FAI appear generally at 80-110 km altitudes during 1800-0400 hrs LT, and FAI occur most frequently at 2200 hrs LT. Further, among the four different echo types, the occurrence probability of NQP is greater than other types.

004125   Dwivedi B N (Applied Physics Dep, Institute of Technology, Banaras Hindu university, Varanasi-221 005, Email: bholadwivedi@gmail.com) : Hinode probes the sun's mysteries. Curr Sci 2008, 94(5), 562-4.

Investigating the interaction of the Sun's magnetic field with its outer atmosphere, the Hinode spacecraft, with three telescopes on-board, is probing some of the Sun's outstanding riddles; Why a hot corona exists and how it is heated? What drives explosive events such as solar flares and coronal mass ejections; What creates the Sun's magnetic field? Hinode's 'detection of Alfven waves' opens a new era in unlocking the secrets of the Sun.

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002085   Sharaf M A;Sharaf A A (Astronomy Dep, Faculty of Science, King Abdul Aziz Univ, Jeddah, Saudi Arabia) : Data analysis of the mean atmospheric co₂ 1959-2005. Bull pure appl Sci-Sect D 2008, 27(1), 37-46.

An accurate and full data analysis of the monthly mean atmospheric CO₂ since 1959 to 2005 was devolved. The results show that, there is no any doubt that the atmospheric CO, increases with the time. so our planet is getting warmer. The precision criteria of the analysis are very satisfactory and was support graphically and computationally by many tests.

5 illus, 3 tables, 6 ref

002084   Namboodiri P M S (NO, Indian Institute of Astrophysics, Bangalore-560 034, Email: pmsn@iiap.res.in) : Some properties of merger remnants of interacting galaxies modeled as n = 4 polytrope. Bull Astr Soc India 2008, 36(1), 65-76.

Galaxies interact in a multitude of ways with their environment. Such interactions can alter the morphological type of galaxies, trigger star formation and even produce active galactic nuclei. One of the important parameter in a galaxy collision is the impact parameter. Numerical simulations have been performed to study the effect of changing the impact parameter in a galactic collision. The initial density distribution in the galaxy corresponds that of a polytrope of index n = 4. The galaxy model does not include the dark matter halo component and therefore is not expected to mimic all properties of a real galaxy. Both merging and non-merging collisions of equal mass galaxies have been studied to see where the transition occurs between these two processes. Merging occurs when the closest approach distance of the galaxies is less than three times its half-mass radius. The merging time increases with the distance of closest approach. The density profiles of the merger remnants follow a r^1/4 law in the inner parts and deviate from it in the outer regions. Distant encounters do not result in merging and the galaxies remain almost intact with only negligible change in its mass and internal energy.

4 illus, 1 table, 25 ref

002083   Mahdi B (NO, Inter Univ Center for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune-411 007, Email: mahdi@iucaa.ernet.in) : Automated classification of ELODIE stellar spectral library using probabilistic articial neural networks. Bull Astr Soc India 2008, 36(1), 1-54.

A Probabilistic Neural Network model has been used for auto-mated classification of ELODIE stellar spectral library consisting of about 2000 spectra into 158 known spectro-luminosity classes. The full spectra with 561 flux bins and a PCA reduced set of 57, 26 and 16 components have been used for the training and test sessions. The results show a spectral type classification accuracy of 3.2 sub-spectral type and luminosity class accuracy of 2.7 for the full spectra and an accuracy of 3.1 and 2.6 respectively with the PCA set. This technique will be useful for future upcoming large databases and their rapid classification.

5 illus, 7 tables, 14 ref

002082   Chandra S;Shinde S V (School of Physical Sciences, S.R.T.M. Univ, Nanded-431 006) : Anomalous absorption in rhomboidal SiC₃ molecules. Bull Astr Soc India 2008, 36(1), 55-63.

Laboratory detection of two isomers of cyclic SiC₃ molecule have been reported by McCarthy et al. (1999a, 1999b) and Apponi et al. (1999b). Seven transitions of the isomer-I have been detected in IRC+10216 by Apponi et al. (1999a). However, to date, the second isomer is not detected in the interstellar space. Proposes identification of isomer-I through the transition 4₂₂ - 4₂₃ at 0.2 GHz and of isomer-II through the transitions 2₂₀-2₂₁ at 4.44 GHz and 4₄₀-4₄₁ at 2.16 GHz, in absorption against the cosmic microwave background (CMB). In absence of the availability of the collisional rates, we have used scaled values for them. Checkes the sensitivity of the lines on the rates by enhancing the rates for transitions with Δk_a = 0 by a factor of 10 and the results are not found sensitive.

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