018160   Narlikar J V (NO, Inter University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune-411 007, Email: jvn@iucaa,ernet.in) : Early days of general relativity. Curr Sci 2015, 109(12), 2214-19.

This Account deals with the progress of Einstein's general relativity (GR) theory first published in 1915. It will discuss the `bending of light' experiment planned and executed be Eddington in 1919 and then concentrate on the development of GR in India. For, it will be argued that despite the reputation of GR as an obtuse theory it did find fertile soil to grow in India. Tshis account will go as far as the time of India's independence.

24 ref

018159   Mukhopadhyay B (Physics Dep, Indian Institute of Sciences, Bengaluru-560 012, Email: bm@physics.iisc.ernet.in ) : General relativity and relativistic astrophysics. Curr Sci 2015, 109(12), 2250-7.

Einstein established the theory of general relativity and the corresponding field equation in 1915 and its vacuum solutions were obtained by Schwarzschild and Kerr for, respectively, static and rotating black holes, in 1916 and 1963, respectively. They are, however, still playing an indispensable role, even after 100 years of their original discovery, to explain high energy astro- physical phenomena. Application of the solutions of Einstein's equation to resolve astrophysical phenomena has formed an important branch, namely relativistic astrophysics. I devote this article to enlightening some of the current astrophysical problems based on general relativity. However, there seem to be some is- sues with regard to explaining certain astrophysical phenomena based on Einstein's theory alone. I show that Einstein's theory and its modified form, both are necessary to explain modern astrophysical processes, in particular, those related to compact objects.

3 illus, 3 tables, 56 ref

018158   Iyer B R (NO, International Centre for Theoretical Sciences-TIFR, Hessaraghatta, Bengaluru-560 089, Email: bala.iyer@icts.res.in) : Advances in classical general relativity. Curr Sci 2015, 109(12), 2230-5.

The year 2015 is the centenary of Einstein'screation of general relativity. Over the century general relativity has gradually increased its footprints on main-stream physics and this article highlights advances in the classical aspects of general relativity since its creation.

2 tables, 70 ref

018157   Gopakumar R (NO, International Centre for Theoretical Sciences-TIFR, Survey No. 151, Shivakote, Hesaraghatta Hobli, Bengaluru-560 089, Email: rajesh.gopakumar@icts.res.in) : String theory and the conundrums of quantum gravity. Curr Sci 2015, 109(12), 2265-70.

Give a brief survey of the attempts to understand the quantum dynamics of general relativity through the lens of quantum field theory, which has been suc- cessfully applied to the other fundamental interac- tions. This approach began by naively quantizing spin two massless particles but quickly ran into difficulties when considering quantum corrections to the interact- ing theory. We will describe how the early incarna- tions of string theory successfully addressed these problems. Then we go on to sketch how one has been able to go beyond this `perturbative' picture by giving a tight microscopic description of black hole thermo- dynamics. This in turn has led to the much more sub- tle holographic description of the quantum dynamics of a large class of spacetimes which has been one of the primary engines of theoretical developments in the last couple of decades.

2 ref

018156   Dadhich N (Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi-110 025, Email: nkd@iucaa.ernet.in) : General relativity in post-Independence era. Curr Sci 2015, 109(12), 2220-9.

The most outstanding contribution to general relativeity in this era came in 1953 in 1953 (published in 1955 (ref.1)) in the form of the Raychaudhuri equation.It is in 1960s that the observations began to confront the eupherial theory and thus began exploration of GR as a legitimate physical theory in right earnest. The remarkable discoveries of cosmic microwave background radiation, quasars, rotating (Kerr) black hole and the powerful singularity theorems heralded a new canvas of relativistic astrophysics and cosmology. I would attempt to give a brief account of Indian participation in these exciting times.

58 ref

018155   Ashtekar A (NO, Institute for Gravitation and the Cosmos and Physics Dep, Penn State, University Park, PA 16802, USA) : Quantum general relativity. Curr Sci 2015, 109(12), 2243-9.

After a brief historical introduction on quantum gravity as a whole, the current status of loop quantum gravity is discussed. Because of space limitation, I could only illustrate recent advances through one example-cosmology of the very early universe - and provide references for results in other main areas.

1 illus, 33 ref

016133   Singh S K;Rajawat A S;Rathore B P;Bahuguna I M;Chakraborty M (NO, Geo Science and Applications Group, Space Applications Centre (ISRO), Ahamedabad-380 015) : Detection of glacier lakes buried under snow by RISAT-1 SAR in the Himalayan terrain. Curr Sci 2015, 109(9), 1728-32.

Synthetic aperture radar (SAR) signals penetrate through the dry snow and cloud providing crucial data over the Himalayan temperate glaciers and complement the optical images. In the present study, RISAT-1 C band and AWiFS images of winter/ablation period over Samudra Tapu and Gepang Gath moraine dammed lakes (MDLs) in Himachal Pradesh have been analysed. Backscattering coefficient of the lake was observed to be low throughout the year. Penetration depth of SAR into dry snowpack was calculated to vary from 4 to 22 m for a range of snow density (0.1-0.5 g/cm^{3), whereas it was estimated to be 1.20-2.01 m based on ground observations for 30 January and 24 February 2013. The present study provides results of RISAT-1 C-band penetration up to <126>2 m through the snowpack to detect MDLs in the Himalayan terrain. The detection of MDLs using the backscattering images of winter season was validated with synchronous AWiFS sensor images.}

5 illus, 13 ref

016132   Chatterjee A (Physics and Astronomical Sciences Dep, Central Univ of Himachal Pradesh, Kangra-176 215, Email: ayan.theory@gmail.com) : Hawking radiation from quasilocal dynamical horizons. Pramana J Phys 2016, 86(2), 307-14.

In completely local settings, we establish that a dynamically evolving spherically symmetric black hole horizon can be assigned a Hawking temperature and with the emission of flux, radius of the horizon shrinks.

28 ref

015082   Vishnu Nampoothiri M;Sowmianarayanan L; Jayakumar B;Kunhikrishnan P (Vikram Sarabhai Space Centre, Indian Space Research Organisation, Thiruvananthapuram-695 022, Email: p_kunhikrishnan@vssc.gov.in) : PSLV-C25: the vehicle that launched the Indian mars orbiter. Curr Sci 2015, 109(6), 1055-60.

Polar Satellite Launch Vehicle (PSLV) of the Indian Space Research Organisation (ISRO) successfully executed the launch of the Indian Mars Orbiter by precisely placing the spacecraft in the initial Earthbound orbit on 5 November 2013. This was the critical first step of the three-phase Mars Orbiter Mission (MOM). The focus of this article is on the major challenges tackled by the launch vehicle project team in designing, planning and executing MOM.

6 illus, 2 ref

015081   Sridhar R V L N;et. al. (Laboratory for Electro-optics Systems, Indian Space Research Organisation, Bengaluru-560 058, Email: mvis@leos.gov.in) : Lyman alpha photometer: a far-ultraviolet sensor for the study of hydrogen isotope ratio in martian exosphere. Curr Sci 2015, 109(6), 1114-20.

The Lyman Alpha Photometer (LAP), developed for flight on the Mars Orbiter Mission (MOM) spacecraft in 2013, is primarily designed to measure deuterium to hydrogen abundance ratio of the Martian exosphere over a 6-month period from a 263 km x 71,358 km elliptical orbit around Mars. A set of ultrapure (99.999%) hydrogen and deuterium gas-filled cells comprising tungsten filaments, a 25 mm diameter collection lens and a solar-blind photomultiplier tube together with an 8 nm bandpass Lyman alpha filter are the principal electro-optical assemblies of the instrument. This article presents scientific objectives of LAP and its performance specifications along with details of instrument design. The ground characterization techniques to assess LAP operational performance are also presented. End-to-end test results and evaluation matrix of LAP were satisfactory, well within the desired specifications. The first LAP onboard operation was carried out during the cruise phase of MOM spacecraft journey to verify its functionality and all recorded on-board health parameters were satisfactory.

7 illus, 2 tables, 27 ref

015080   Singh R P;et. al. (Space Applications Centre, Indian Space Research Organisation, Ahmedabad-380 058, Email: rpsingh@sac.isro.gov.in) : Thermal infrared imaging spectrometer for mars orbiter mission. Curr Sci 2015, 109(6), 1097-105.

Thermal Infrared Imaging Spectrometer (TIS), which operates in the infrared spectral region (7-13 μm), is one of the five instruments on-board the Mars Orbiting Mission (MOM). TIS was designed to detect emitted thermal infrared radiation from the Martian environment, which would enable the estimation of ground temperature of the surface of Mars and also map its surface composition. TIS instrument is a grating-based spectrometer which has spatial resolution of 258 m at periapsis (372 km). TIS hardware was realized with light-weight miniaturized components (total weight 3.2 kg) with power requirement of 6 W. Observations from TIS instrument were carried out during Earth-bound manoeuvres and cruise phase operations of MOM and the results were found to be in agreement with the laboratory measurements.

15 illus, 10 ref

015079   Mondal S;Bhattacharya A B (Physics Dep, Darjeeling Government College, Darjeeling-734 101, Email: bhattacharyaasitbaran@gmail.com) : Climatic variance and its effects on decametric jovian signal reception at a high altitude station Darjeeling. Indian J Radio Space Phys 2015, 44(3), 126-31.

In this paper precipitation, firing related to extraterrestrial bodies and other ionospheric effects on decametric Jovian radio signal reception at high altitude has been discussed. Jovian signal is observed at 20.1 MHz in the observatory installed at Darjeeling. As Jovian signal is studied under light of Jupiter-Io coupling, it is found that rainfall, out of different atmospheric components, has highest potential to influence reception of Jovian non-Io emission. The observations show that rainfall density plays crucial role in screening extra-terrestrial signal reception from Earth based observatories. The primitive study also suggests that cumulonimbus cloud may have effect on radio signal reception at high altitude. Some interesting findings regarding climatic influence on Jovian signal reception are reported in this paper.

10 illus, 20 ref

015078   Mathew K;et. al. (Space Applications Centre, Indian Space Research Organisation, Ahmedabad-380 058, Email: kurian_mathew@sac.isro.gov.in) : Methanae sensor for mars. Curr Sci 2015, 109(6), 1087-96.

Methane Sensor for Mars (MSM), on-board Mars Orbiter Mission is a differential radiometer based on Fabry-Perot Etalon (FPE) filters which measures column density of methane in the Martian atmosphere. It is the first FPE sensor ever flown to space. Spectral, spatial and radiometric performances of the sensor were characterized thoroughly during the pre-launch calibration. Geophysical calibration of the sensor was carried out using the data acquired over Sahara desert during Earth Parking Orbit phase. Retrieval algorithm for MSM, which is based on the linearization of radiative transfer equations, gets simultaneous solutions for CH₄ and CO₂ concentrations in the Martian atmosphere.

19 illus, 3 tables, 14 ref

015077   Karidhal R;Harinath N;Robert P;Kesavaraju V (Mission Development Group, Indian Space Research Organisation Satellite Centre, Bengaluru-560 017, Email: kesava@isac.gov.in) : Mission automation and autonomy for the mars orbiter mision. Curr Sci 2015, 109(6), 1070-5.

For interplanetary missions such as the Mars Orbiter Mission (MOM), operating at considerable distances from the Earth, the paradigms of autonomy and automation are especially pertinent. For mission autonomy, the reasons are identified to extend the existing features and adding new mechanisms on-board the spacecraft, which were not available in earlier satellites. For mission automation, space segment and ground segment elements such as mission planning system and automation in the control room are reviewed and necessary elements added. For interplanetary missions where distances and times for to and fro travel are more, S/C has to micro manage itself. Therefore it would be essential to use on-board to use on-board autonomy to recognize problems on-board the spacecraft and fix them automatically. Thus, autonomous fault detection becomes vital for such long-term, long-distance missions. Various FDIR (Fault Detection, Isolation and Reconfigure) logics were proposed to be added to take care of several autonomy actions. Safe mode recovery and reconfiguration is one of the most critical autonomy features as the ground intervention is not possible till the on-board antenna is automatically oriented towards Earth by the spacecraft. Similarly, mission automation concepts have been added for various operations with known timelines such as performing Mars Orbiter Insertion operation through an on-board sequencer and various payload operations within an orbit using CCB and Macros features of the on-board TCP processor. One of the most important aspects of mission automation is mission planning, i.e. to work out a proper timeline for all onboard and ground operations using an Executive Scheduler on ground and make the spacecraft ready to take actions based on set timelines.

5 illus, 1 table, 3 ref

015076   Kane R P (NO, Instituto Nacional de Pesquisas Espacias, INPE CP 515, 12201-970 Sao Jose dos Campos, SP, Brazil, Email: rajaram.kane@inpe.br) : Solar cycle variation of coronal green line index. Indian J Radio Space Phys 2015, 44(3), 122-5.

During 1966-2008 (solar cycles 20-23), the evolutions of sunspots (Rz) and solar flare index (SF) show similar evolution, i.e. a rising phase, a broad maximum and a declining phase in each cycle. On the other hand, coronal holes are more frequent in the declining phase of each cycle. Hence, the coronal green line index (CG), which represents coronal heating, is expected to be similar to sunspots and solar flare index during the rising and maximum phases of solar cycle but dissimilar in the declining phase. Observations show that this was true, but the excess of CG in the declining phase is small compared to the CG intensities at solar maximum. Thus, the contribution of coronal hole could not be unique or even major one for the large coronal heating. There are many solar parameters which evolve differently from the sunspot numbers. But in the present paper, it is assumed that comparison with sunspot numbers may be a reasonable one.

1 illus, 15 ref

015075   Joseph O;Johnson A O (Physics Dep, Federal Univ, Lafia, P M B 146, Lafia, Nigeria, Email: omojola.josef@gmail.com) : GNSS positioning accuracy over Nigeria during geomagnetic storm of 24-27 october 2011 and 7-10 october 2012. Indian J Radio Space Phys 2015, 44(3), 138-46.

The present work investigates the positioning error of five Nigeria GNSS network stations during the geomagnetic storm of 24-27 October 2011, a sudden storm commencement (SSC) with disturbance storm time (Dst) minimum of -134 nT; and 7-10 October 2012, a gradual storm commencement (GSC) with Dst minimum -105 nT. Satellite data were obtained from Nigeria GNSS network stations and Dst values were obtained from World Data Center (WDC) for Geomagnetism Kyoto, Japan while the quiet period was selected with Ap index of zero (0) and one (1) for the two storms, respectively from the same World Data Center. RTKLIB (version 2.4.2), a GNSS analysis software, was used to determine the positioning of the stations during the selected storm period and quiet period and the results were analyzed using MATLAB. This investigation revealed that during the selected storm period, the positioning error of the stations increase; though the two storms do not show the same characteristics on GNSS positioning. The GSC of 7-10 October 2012 showed a latitudinal effect, which may be as a result of local variation in the electron density and enhancement of ionospheric irregularity during the storm. This was not clearly depicted in the SSC of 24-27 October 2011.

13 illus, 10 tables, 10 ref

015074   Gupta S P;Thampi S V (NO, Physical Research Laboratory, Navarangpura, Ahmedabad-380 009, Email: spg@prl.res.in) : Electrical conductivity of the stratosphere over Hyderabad, India: results from balloon borne measurements. Indian J Radio Space Phys 2015, 44(3), 132-7.

Stratospheric conductivity is an important parameter of the global electric circuit. In this paper, the stratospheric conductivity measurements are presented, which were made using high altitude balloon flights from Hyderabad (geographic 17.5°N, 78.5°E; magnetic lat 8.5°N), India as a part of the IMAP (1982-1994) program of India. The vertical profiles of ion conductivity were measured from Hyderabad during periods with different solar activity levels and during different seasons using different techniques. It was observed that conductivity values in stratosphere are larger in high solar activity period as compared to low solar activity period. This is similar in nature to the observations from mid-latitudes. The observed positive correlation with solar activity is discussed in terms of composition changes due to the change in intensity of the UV (200-300 nm) radiation with solar activity. It was found that the dissociation of heavy cluster ions to lighter ions, as conjectured by Gupta [Solar cycle variation of stratospheric conductivity over low latitude, Adv Space Res (UK), 26 (2000.) pp 1225-1229] is the main reason for the observed positive correlation of stratospheric conductivity with solar activity. No significant seasonal effect was noticed. In addition, conductivity profile obtained from Hyderabad is compared to that obtained from Cachoeira Paulista, Brazil.

4 illus, 22 ref

015073   Bhardwaj A;et. al. (Vikram Sarabhai Space Center, Indian Space Research Organisation, Thiruvananthapuram-695 022, Email: anil_bhardwaj@vssc.gov.in) : MENCA experiment aboard India's mars orbiter mission. Curr Sci 2015, 109(6), 1106-13.

The Mars Exospheric Neutral Composition Analyser (MENCA) aboard the Indian Mars Orbiter Mission (MOM) is a quadrupole mass spectrometer-based experiment. Making use of the highly elliptical and low inclination (<126> 150°) orbit of MOM, MENCA will conduct in situ measurements of the composition and radial distribution of the Martian neutral exosphere in the 1-300 amu mass range in the equatorial and low latitudes of Mars. The functionality of MENCA has been tested during the Earth-bound and heliocentric phases of MOM before its operation in the Martian orbit. This article describes the scientific objectives, instrument details, design and development, test and evaluation, and calibration of the MENCA instrument.

13 illus, 1 table, 18 ref

015072   Bendict Lawrance M;Shanmugaraju A;Prasanna Subramanian S (NO, Sethu Institute of Technology, Kariapatti, Virudhunagar Dist 626 115, Email: lorentz.ben@gmail.com) : Investigations of slow and fast coronal mass ejections and their associated activities in solar cycle 24. Indian J Radio Space Phys 2015, 44(3), 113-21.

Present papers compares the properties of slow and fast coronal mass ejections (CMEs) associated with intensive flare (<62>M5.0 X-ray class) during 2008-2013 in solar cycle 24. The CMEs are separated into two groups based on speed: Group I containing 31 CME events with speed below 900 km s^{-1 and Group II containing 27 CME events with speed above 900 km s-1. The mean CME speeds of Groups I and II are found to be 558 and 1629 km s-1, respectively and the mean CME width of the Group II is slightly higher than Group I. The CMEs of Group II are highly decelerated than the CMEs of Group I. It is found that the rise time and duration of intensive flares of Group II is slightly greater than those of Group I. While 60% of Group I events are located on the southern hemisphere, 85% of Group II events are located on the northern hemisphere. Further, the number of halos, DH type IIs, Solar energetic particle (SEP) events associated with Group II are 2, 3 and 6 times, respectively that of Group I. Utilizing the density models of suitably connecting the corona and interplanetary medium, the shock formation height of DH type radio bursts are found to be in the height range 2-6 R_o and the maximum estimated distance of shock are found to be in the height range 16-215 R_o. The mean shock speed of Group I and Group II events (599 and 1359 km s-1, respectively) are in agreement with the CME speed. On comparison of slow and fast events, the faster events are found to be mostly decelerated, mostly associated with stronger storms, more number of DH type II bursts and SEPs.}

6 illus, 4 tables, 21 ref

015071   Arya A S;et al. (Space Applications Centre, Indian Space Research Organisation, Ahmedabad-380 015, Email: arya_as@sac.isro.gov.in) : Mars colour camera: the payload characterization/calibration and data analysis from earth imaging phase. Curr Sci 2015, 109(6), 1076-86.

Mars Colour Camera (MCC) on-board Mars Orbiter Mission is considered the 'eye' of the mission, taking photographs (imageries) of the surfacial features on Mars, and the cloud and dust around it. MCC is an important contextual camera for other non-imaging sensors like MSM, TIS, LAP, etc. The camera has been designed, characterized, calibrated and qualified at the Space Applications Centre, ISRO, Ahmedabad by a team of professional engineers and scientists. It has been miniaturized, ruggedized and space-qualified to match the weight and power budget of the mission. During Earth orbit phase, the images returned by the camera have been analysed qualitatively and quantitatively. The results show that MCC has been working as expected in terms of radiometry, geometry and application potential to discern various morphological features. The present article discusses these facts in detail.

20 illus, 5 ref

015070   Arunan S;Satish R (NO, Indian Space Research Orgainisation Satellite Centre, Bengaluru-560 017, Email: arunan@isac.gov.in) : Mars orbiter mission spacecraft and its challenges. Curr Sci 2015, 109(6), 1061-9.

Mars Orbiter Mission (MOM), India's first interplanetary mission, was launched on 5 November 2013 from the Satish Dhawan Space Centre (SDSC), Sriharikota, using PSLV XL C-25 rocket. MOM spacecraft was successfully inserted into the Martian orbit on 24 September 2014. One of the main objectives of the mission to Mars is to develop the technologies required for design, planning, management and operation of an interplanetary mission. Scientific objectives include exploration of surface features of Mars, morphology, topography, mineralogy and study of Martian atmosphere using indigenous scientific instruments. The spacecraft configuration is a balanced mix of design from flight-proven IRS/INSAT/Chandrayaan-1 bus. The configuration and subsequent design of the spacecraft had to take into consideration the many challenges it would face during its mission life. The spacecraft has been designed for interplanetary missions capable of operating in Earth burn, Mars transfer trajectory and Martian orbit environments. The major challenges of design are in thermal environment, radiation environment, power systems, communication systems, propulsion systems and on-board autonomy.

8 illus, 7 ref

015069   Adimurthy V (Space Dep, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022, Email: vip.adimurthy@gmail.com) : Concept design and planning of India's first interplanetary mission. Curr Sci 2015, 109(6), 1050-4.

In the quest for planetary exploration, Mars holds a special position in view of the many similarities it has with Earth. This article highlights the significant aspects of the concept design and planning which paved the way for the successful Indian Mars Orbiter Mission (MOM). Lessons learnt from historical failures of Mars missions are summarized. The main driving factors of the MOM design are reliability, optimal utilization of existing launch systems, and minimum energy orbit placement around Mars with an innovative, highly elliptic orbit. An exposition of the mission strategy, trajectory design, technological features and science goals is also presented. The article concludes with a glimpse into the possible future Mars mission challenges to humanity.

1 illus, 1 table, 14 ref

013042   Rastogi R G;Chandra H (NO, , Physical Research Laboratory, Ahmedabad-380 009, Email: hchandra@prl.res.in ) : Equatorial electrojet in the African sector. Indian J Radio Space Phys 2015, 44(4), 187-98.

Hourly values of the deviations in the geomagnetic X and Y field at two equatorial electrojet stations in Africa, viz. Freetown (FTN) on the western part and Addis Ababa (AAE) on the eastern part, are studied for three years 1962-64. The declination is almost along the geographic N-S at AAE and 14° towards west of the geographic N-S at FTN. The annual mean daily range in X is around 80 nT at FTN and 70 nT at AAE with peak around 1100 hrs LT. Deviations in Y at FTN show a broad minimum of about -20 nT around noon while the decrease is much smaller at AAE with a minimum of -5 nT at noon. Seasonal mean variations of the daily range in X show almost equal peaks during December solstice and equinox at FTN but at AAE it is highest during equinoctial months and lowest during June solstice. The seasonal asymmetry at FTN could be due to large declination. The equinoctial peak in March - April is higher than the peak in September - October at both the stations. Another notable feature at FTN is the steady increase in deviation in X from about -10 nT at 1800 hrs LT to 10 nT at 0600 hrs LT. The direction of the H vector is aligned almost along the geographic N-S for December solstice and equinox at AAE and along 12° W of north during June solstice. At FTN, it is aligned along about 5° W of north during D and E-months and to about 20° W of north during June solstice.

11 illus, 44 ref

013041   Rastogi R G;Chandra H (NO, , Physical Research Laboratory, Ahmedabad-380 009, Email: hchandra@prl.res.in ) : Spread F at tropical latitude stations in India. Indian J Radio Space Phys 2015, 44(4), 177-86.

Regular radio soundings of the ionosphere over Ahmedabad were started in 1953 and several studies describe the various features of the ionosphere close to the equatorial ionization anomaly crest. Finer characteristics of the spread F echoes could not be studied earlier due to the very wide pulse of the transmitter. The characteristics of the spread F at Ahmedabad are described in the present paper using the recordings of recently installed Digisonde during June - July 2012. The spread F echoes at Ahmedabad are not due to the in situ produced irregularities as at an equatorial station Thumba. The spread F echoes at Ahmedabad during the June solstices of 2012 are due to reflection (not scattering) from the off-vertical direction that produce multiple traces from off-vertical direction overlapping over the main (vertical) h'-f trace, sometimes giving an appearance of diffuse echoes near the critical frequencies. Presence of medium scale traveling ionospheric disturbances (TIDs) could be a possibility to account for such off-vertical reflections.

6 illus, 41 ref

013040   Motty G S;Satyanarayana M;Jayeshlal G S; Krishnakumar V;Pillai V P M (Optoelectronics Dep, Keral Univ, Kariavottom, Trivandrum-695 581, Email: mottygs@gmail.com) : Optical properties of cirrus clouds in the tropical troopause region during two contrasting seasons. Indian J Radio Space Phys 2015, 44(4), 155-66.

Radiation budget of Earth's atmospheric system is largely impacted by the presence of cirrus clouds. In order to quantify the effect of cirrus clouds, particularly in tropics, it is important to characterise its vertical structure and optical properties. The variation of the optical and microphysical properties along with the structure and dynamics of the cirrus during two contrasting seasons, the summer and the southwest monsoon over the period 2006 - 2010 were studied using the ground-based lidar measurements made at the tropical station, Gadanki (13.5°N, 79.2°E), India. The related meteorological indicators derived from radiosonde data available with Wyoming Atmospheric Data Centre were analysed. The results were compared with the data obtained from the CALIOP on board the CALIPSO satellite. Both the observations show similar pattern of seasonal variation. In most of the cirrus clouds, the top height observed was 0.8 km above and below the tropopause and top height was maximum during monsoon season. The seasonal variation of optical depth showed that most of cirrus clouds were thin and the optical depth showed highest value during monsoon period.

11 illus, 3 tables, 27 ref

013039   Dharwan M;Singh V (Physics Dep, Indian Institute of Technology Roorkee, Roorkee-247 667) : Study of O<. Indian J Radio Space Phys 2015, 44(4), 167-76.

Effect of geomagnetic storms on O^{+(2P-2D) 732.0 nm dayglow emission is studied using recently updated photochemical model of Thirupathaiah et al. [An updated model of O+(2P) 7320 armstrung dayglow emission, Indian J Radio Space Phys, 44 (2015), 7]. Three geomagnetic storms, which occurred on 23-27 August 2005, 13-17 April 2006 and 1-5 February 2008 are chosen in the present study. A negative correlation is found between the volume emission rate (VER) and the Dst index for all the three geomagnetic storms. The present study shows that the relative variation of VER with respect to the initial value of VER (before the onset of a geomagnetic storm) during the main phase increases above 260 km. It is also found that the altitude of the peak emission rate does not show any appreciable variation with the activity of geomagnetic storm. A positive correlation is found between the zenith intensity and the atomic oxygen number density. The atomic oxygen number density obtained from NRLMSISE-00 model is compared with the measurements of Earle et al. [Low latitude thermospheric responses to magnetic storms, J Geophys Res (USA), 118 (2013), 3866] during a geomagnetic storm. This comparison shows that the atomic oxygen number density as provided by NRLMSISE-00 model is significantly lower than the measured value. Consequently, the atomic oxygen number density is treated as a variable parameter in the photochemical model and its effect on the VER of 732.0 nm dayglow emission is further studied. The zenith intensity is found to increase about 70% even in the case of weakest storm when the atomic oxygen number density is doubled. The latitudinal effect on the VER and zenith intensity of 732.0 nm is also studied. It is found that the VER decreases as the latitude increases. The decrease in VER from low to mid latitudes is due to the decrease in atomic oxygen number density with latitude. The zenith intensity at the maximum geomagnetic activity is about 12% higher than the zenith intensity before the start of the geomagnetic storm in equatorial region. However, no appreciable change in the zenith intensity is found at higher latitudes.}

11 illus, 36 ref

013038   Chandrasekaran P;Balasubramanyam R (Astronomy & Astrophysics Group, Raman Research Institute, Bangalore-560 080) : Systematic study of coding performance in a MIMO-STBC-OFDM link. IETE J Res 2015, 61(1), 56-64.

MIMO-STBC-OFDM systems mitigate inter symbol interference and frequency-selective fading caused by multi-path propagation in modern high-data-rate wireless communication. Error correction codes use redundancy to correct errors that still occur. No systematic analysis of their performance using a common link configuration is found in the literature. We fill this gap in this simulation study using a common MIMO-STBC-OFDM communication link, transferring data at a symbol rate of 100 Mbps. We find that (a) for all code rates, low-density parity-check code performs best with BPSK and to an extent with QPSK and (b) 1/2-rate convolutional code works well for all symbol mapping schemes.

5 illus, 1 table, 20 ref

013037   Alad R H;Chakrabarty S B (Electronics and Communication Dep, Faculty of Technology, Dharmsinh Desai Univ, Nadiad-387 001, Email: rizwan_alad@yahoo.com) : Evaluation of capacitance matrix of artificial orbiting satellites. Indian J Radio Space Phys 2015, 44(4), 199-204.

Paper presents the evaluation of capacitance matrix of an artificial orbiting satellite considering a composite metallic structure of a parabolic reflector antenna with cuboid and plates. Integral equations are formed by relating the unknown charge density on the metallic conductor and are solved using the Method of Moments (MoM) in which the pulse functions are used as basis functions and the delta functions are used as testing functions. The surfaces of the conducting structure are meshed using non-uniform triangular patches. The matrix equations are solved by iterative generalized minimum residual (GMRES) algorithm. The numerical data on the capacitance matrix and charge distribution of these structures have been presented. The capacitance of a metallic cuboid is computed to validate the approach.

3 illus, 3 tables, 12 ref

012113   Senger P (NO, GSI Helmholtzzentrum fiir Schwerionenforchung GmbH, Planckstr.1, 61291 Darmstadt, Germany and Johann Wolfgang Goethe Univ, Frankfurt am Main, Germany) : Exploring Nuclear Matter at Neutron Star core densities. Proc Indian Natn Sci Acad 2015, 81(1), 296-308.

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At top RHIC and LHC energies, the QCD phase diagram is studied at very high temperatures and very low net-baryon densities. These conditions presumably existed in the early universe about a microsecond after the big bang. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure such as a critical point, a first order phase transition between hadronic and partonic matter, or new phases like quarkyonic matter. The experimental discovery of these prominent landmarks of the QCD phase diagram would be a major breakthrough in our understanding of the properties of nuclear matter. The Compressed Baryonic Matter (CBM) experiment will be one of the major scientific pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. The goal of the CBM research program is to explore the QCD phase diagram in the region of high baryon densities using high-energy nucleus-nucleus collisions. This includes the study of the equation-of-state of nuclear matter at neutron star core densities, and the search for the deconfinement and chiral phase transitions. The CBM detector is designed to measure rare diagnostic probes such as multi-strange hyperons, charmed particles and vector mesons decaying into lepton pairs with unprecedented precision and statistics. Most of these particles will be studied for the first time in the FAIR energy range. In order to achieve the required precision, the measurements will be performed at very high reaction rates of 1 to 10MHz. This requires very fast and radiation hard detectors, and a novel data read-out and analysis concept based on free streaming front-end electronics and a highperformance computing cluster for online event selection. The layout, the physics performance, and the status of the proposed CBM experimental facility have been discussed in the present manuscript.

9 illus, 13 ref

012112   Saha S (Physics Dep, Sarojini Naidu College for Women, Kolkata-700 028, Email: snl.saha@yahoo.com) : Accretion dynamics in SdS space. Proc Indian Natn Sci Acad 2015, 81(1), 282-97.

Generally a centrally located accreting super massive (<126> 10^{8M_) black hole is thought to be playing the role of the gravitational powerhouse of gigantic scale in AGN. The accretion process for such a black hole may be studied using general relativistic as well as post Newtonian scheme for various possible flow geometries with different equation of states of the accreted matter. For the sake of simplicity, hydro-dynamical flow models are generally adopted to get an analytical estimate for those accretion process. In our work, accretion process over a region far beyond the dimension of a single galaxy by a much more massive object (<126> 1018M_, a cluster of galaxies or a possible super-giant black hole) has been studied where the large scale feature of the space-time structure of the Universe may be relevant. In the non-rotating limit of the accreting black-hole with accelerated expansion of the Universe, Schwarzschild-de Sitter (SdS) space is chosen to be a suitable one. Pseudo-Newtonian potential describing the gravitational field of static and spherically symmetric black holes in the Universe with a repulsive cosmological constant, i.e. for SdS space, has been recently introduced by Stuchlik and Kovar. Using this potential, here we have studied the phase topology of the flow and also the possibility of formation of stationary shocks both in adiabatic and isothermal limits in accretion discs. In AGN, the existence of stationary shock is believed to be a plausible explanation of the extremely hot annular region there. In our study, in adiabatic (and in isothermal) cases, a significant region of parameter space allow shock formation and those regions shift in comparison with the same for Schwarzschild case due to the effect of cosmological constant in SdS space.}

3 illus, 7 ref

012111   Roy N (Physics Dep, Indian Institute of Technology Kharagpur, Max-Planck-Institute fur Radioastronomie MPIfR, Auf dem Hugel 69, Bonn, D-53121, Germany, Kharagpur-721 302, Email: nroy@mpifr.de) : Multiphase turbulent interstellar medium: some recent results from radio astronomy. Proc Indian Natn Sci Acad 2015, 81(3), 583-97.

Radio frequency 1.4 GHz transition of the atomic hydrogen is one of the important tracers of the diffuse neutral interstellar medium. Radio astronomical observations of this transition, using either a single dish telescope or an array interferometer, reveal different properties of the interstellar medium. Such observations are particularly useful to study the multiphase nature and turbulence in the interstellar gas. Observations with multiple radio telescopes have recently been used to study these two closely related aspects in greater detail. This review article presents a brief outline of some of the basic ideas of radio astronomical observations and data analysis, summarizes the results from these recent observations, and discusses possible implications of the results. Using various observational techniques, the density and the velocity fluctuations in the Galactic interstellar medium was found to have a Kolmogorov-like power law power spectra. The observed power law scaling of the turbulent velocity dispersion with the length scale can be used to derive the true temperature distribution of the medium. Observations from a large ongoing atomic hydrogen absorption line survey have also been used to study the distribution of gas at different temperature. The thermal steady state model predicts that the multiphase neutral gas will exist in cold and warm phase with temperature below 200 K and above 5000 K respectively. However, these observations clearly show the presence of a large fraction of gas in the intermediate unstable phase. These results raise serious doubt about the validity of the standard model, and highlight the necessity of alternative theoretical models. Interestingly, numerical simulations suggest that some of the observational results can be explained consistently by including the effects of turbulence in the models of the multiphase medium.

10 illus, 72 ref

012110   Panda N R;Mohanta K K;Sahu P K (NO, Institute of Physics, Sachivalaya Marg, Bhubaneswar-751 005, Email: niharphy@iopb.res.in) : Maximum mass and radial modes of hybrid star in presence of strong magnetic field. Proc Indian Natn Sci Acad 2015, 81(1), 256-66.

It is believed that neutron stars (NS) consist of hadronic and exotic states like strange quark or color superconducting matter. Stars having a quark core surrounded by a mixed phase followed by hadronic matter, may be considered as hybrid stars (HS). The mixed phase is well proportionate of both the hadron and quark phases. A huge magnetic field is predicted in core as well as on surface of the neutron star. Here we study the effect of this strong magnetic field on the equation of states(EOS) of HS matter. We further study the hadron-quark phase transition in the interiors of NS giving rise to HS in presence of strong magnetic field. We finally study the effect of strong magnetic field on maximum mass and eigenfrequencies of radial pulsation of such type of HS. For the EOS of hadronic matter, we have considered RMF(Relativistic Mean Field) theory and we incorporated the effect of strong magnetic fields leading to Landau quantization of the charged particles. For the EOS of quark phase we use the simple MIT bag model. We have assumed Gaussian parametrization to incorporate the density dependence of both bag pressure and magnetic field. We have constructed the intermediate mixed phase by using Glendenning conjecture. We found that magnetic field softens the EOS of both the phases, as a result the maximum mass is reduced for HS and period of oscillation is increased significantly for primary mode.

3 illus, 33 ref

012109   Pal K (Physics Dep, Serampore College, Serampore-712 201, Email: kausik.sinp@gmail.com) : Cooling of neutron star including magnetic interaction. Proc Indian Natn Sci Acad 2015, 81(1), 251-5.

In this work we calculate the neutrino mean free path (MFP) and neutrino emissivity with non-Fermi liquid (NFL) corrections of degenerate quark matter. Subsequently the role of these NFL corrections on the cooling of neutron star has been demonstrated. The cooling curve shows moderate enhancement due to this NFL corrections.

2 illus, 8 ref

012108   Dey S;Maulik A;Raha S;Saha S;Syam D (Center for Astroparticle Physics and Space Science, Bose Institute, Kolkata-700 091, Email: atanu@iopb.res.in) : Characterization of polyethylene terephthalate (PET) detector to search for rare events in cosmic rays. Proc Indian Natn Sci Acad 2015, 81(1), 233-6.

Particular brand of commercially available plastic, identified as polyethylene terephthalate (PET) has been used as a Nuclear Track Detector (NTD) to detect heavy charged particles. It was found that PET has a much higher detection threshold compared to other commercially available NTDs, making PET particularly suitable for detecting rare events in cosmic rays. To characterize and calibrate PET, systemetic studies were carried out using ions from various accelerators in India and Europe. Results of those studies have shown that PET can be effectively used as a charge particle detector with good energy and charge resolution.

2 illus, 5 ref

012107   Biswas S;De J N;Joarder P S;Raha S;Syam D (Physics Dep, Bose Institute, 3/1 APC Road, Kolkata-700 009, Email: sayan@jcbose.ac.in) : Disassembly model for the production of astrophysical strangelets. Proc Indian Natn Sci Acad 2015, 81(1), 277-81.

Determination of the baryon number (or mass) distribution of the strangelets, that may fragment out of the warm and excited strange quark matter (SQM) ejected in the merger of strange stars (SSs) in compact binary stellar systems of the Galaxy, is attempted by using a statistical multifragmentation model (SMM). Finite mass of strange quarks is taken into account in the analysis. Strangelet charge and the resulting Coulomb corrections are included to get a realistic mass distribution of galactic strangelets at their source.

2 illus, 13 ref

012106   Atreya A;Sarkar A;Srivastava A M (NO, Institute of Physics, Bhubaneswar-751 005, Email: atreya@iopb.res.in) : Nuggets anti-nuggets formation from QCD Z(3) domains. Proc Indian Natn Sci Acad 2015, 81(1), 237-43.

Authors investigate the possibility of segregation of baryons and anti-baryons in the quark-gluon plasma phase in the early universe due to CP violating scattering of quarks and antiquarks from moving Z(3) domain walls. CP violation here is spontaneous in nature and arises from the nontrivial profile of the background gauge field (A₀) between different Z(3) vacua. We study the effect of this spontaneous CP violation on the baryon transport across the collapsing large Z(3) domain walls (which can arise in the context of certain low energy scale inflationary models). Our results show that this CP violation will lead to the segregation of baryons and anti-baryons in early universe near the confinement-deconfinement phase tranition epoch. We discuss consequences of this baryon anti baryon segregation in the subsequent cosmological evolution.

3 illus, 21 ref

012105   Adhya S P;Roy P K (High Energy Nuclear and Particle Physics Div, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-757 043, Email: souvikpriyam.adhya@saha.ac.in) : Modification of kick velocity of neutron stars due to non-fermi liquid effects. Proc Indian Natn Sci Acad 2015, 81(1), 288-95.

In this present work we have incorporated the non-Fermi liquid behavior into the expression of the neutron star (NS) kick velocity due to asymmetric neutrino emission. We have studied leading order (LO) as well as next to leading order (NLO) corrections to the velocity and compared the results with the Fermi liquid case. We have approximated our results for the case of large magnetic fields found in NS.

2 illus, 18 ref

007983   Nityananda R (Azim Premji Univ, PES Institute of Technology Campus, Pixel Park, B Block Electronics City, Hosur Road, Bengaluru-560-100, Email: rajaram.nityananda@gmail.com) : Discovering the rotation of our own galaxy. Resonance 2015, 20(10), 869-79.

In the early twentieth century, the Dutch astronomer, Jan Oort, made brilliant use of the two most basic measurements of the motions of nearby stars. These are motions away or towards the Sun based on the Doppler effect, and motion perpendicular to the line of sight, measured as a slow change in the position of the star on the sky. He was able to draw far-reaching conclusions about the rotation and the mass of the Milky Way galaxy in which our Sun is located. His arguments and calculations were based on a simple dynamical model. This model is introduced and described in this article. It can serve as an excellent exercise in an undergraduate physics course, illustrating both mechanical principles and basic astronomy.

007982   Nagar A;Mishra S D;Vijay S K (Physics Dep, S M S Govt Model Science College, Gwalior-474 001, Email: nagaranjugwl@rediffmail.com) : Correlation of foF2 and M(3000)F2 over low latitude stations during low solar activity period. Indian J Radio Space Phys 2015, 44(2), 78-87.

This paper aims to investigate the relationship between propagation parameter M(3000)F2 and F2-layer critical frequency (foF2) during 2006-2010. Data from three low latitude stations, namely Jicamarca (12°S, 283°E), Kwajalein (09°N, 167°E) and Madimbo (22°S, 031°E) for the months of January (winter) and July (summer) during 2006-2010 are used for the study. It is found that the daily values of M(3000)F2 cannot be estimated from foF2 using a simple linear equation. It is concluded that that two procedures (day-to-day and hour-to-hour) do not give different results and the correlation coefficients between the daily values of M(3000)F2 and foF2 are generally lower than 0.6 and could be positive or negative.

3 illus, 2 tables, 23 ref

007981   Dwivedi A K;Sunil Kumar;Tiwari M S (Physics Dep, Harish Chandra P G College, Varanasi-221 001, Email: akdwiv@yahoo.co.in) : Kinetic alfven wave with loss-cone distribution function in the presence of beam velocities in an inhomogeneous magnetosphere. Indian J Radio Space Phys 2015, 44(2), 69-77.

Kinetic Alfven waves in the presence of an inhomogeneous electric field applied perpendicular to the ambient magnetic field with loss-cone distribution function and ion and electron beam are investigated. The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of a kinetic Alfven wave. Expressions are found for the field-aligned current, the perpendicular current and the dispersion relation. The growth/damping rate of the wave is obtained by an energy conservation method. The effect of electron and ion beam, steepness of loss-cone and inhomogeneity of electric field are discussed. The plasma under consideration is assumed to be anisotropic and with low β. The results are interpreted for the space plasma parameter appropriate to the auroral acceleration region of the earth's magnetosphere.

11 illus, 29 ref

007980   Bhattacharya A B;Raha R;Pandit J;Sarkar S; Sarkar S;Mondal S (Physics Dep, Kalyani Univ, Kalyani-741 235, Email: bhattacharyaasitbaran@gmail.com) : Pre-monsoon thunderstorms over Kalyani from radio frequency spectra. Indian J Radio Space Phys 2015, 44(2), 96-101.

Lightning in the form of electromagnetic radiation, in very low frequency (VLF) and low frequency (LF) bands, is received on 1 April and 7 April 2015 from 10 kHz to 300 kHz over Kalyani during pre-monsoon thunderstorms. Their characteristics, viz. the spectral pattern and other relevant properties, are examined with the help of radio frequency (RF) spectra. Another severe thunderstorm experienced, over a wide area covering different parts of South Bengal including Kalyani, on 11 April 2013 has also been recorded in the form of integrated field intensity of atmospherics at 27 kHz receiver. After analysing, some interesting results are reported related to radio signal reception originating from lightning as electromagnetic radiation.

6 illus, 19 ref

007979   Bardhan A;Sharma D K;Sarvesh Kumar (Physics Dep, Faculty of Engineering and Technology, Manav Rachna International Univ, Faridabad-121 001, Email: bardhan.ananna@gmail.com) : Variability of ion denstity due to solar flares as measured by SROSS-C2 satellite. Indian J Radio Space Phys 2015, 44(2), 88-95.

In the present paper the effect of solar flares on ion density has been studied. The ion densities have been measured for the period 1995-1998 using RPA payload of SROSS-C2 satellite. Solar flare data has been obtained from National Geophysical Data Center (NGDC) Boulder, Colorado (USA). The study indicates considerable decrease (1.2 to 2.8 times) in total ion density during flare time as compared to normal time. Out of four ion species, i.e. O^{+, O2+, H+ and He+, the O+ ion density is most affected by the effects of the flare as measured by SROSS-C2. There is considerable decrease in O+ ion density while O₂+, H+ and He+ density show negligible change during flare time as compared to normal time. Furthermore, relation between change in ion density (ΔN) as a response to change in ion temperature (ΔT) during flare time and normal days has been estimated. A comparison of ion density obtained from SROSS-C2 with IRI-2012 during the flare time indicates an overestimation by IRI-2012.}

5 illus, 2 tables, 29 ref

007978   Bagla J S;Sandhu P K (NO, , IISER Mohali, Knowledge City, SAS Nagar PO Manauli, Punjab-140 306, Email: jasjeet@iisermohali.ac.in) : Gravitational collapse and structure formation in an expanding universe. Resonance 2015, 20(9), 803-15.

Used Newtonian formalism is used to motivate the form of Friedmann equations that describe the expansion of the universe in the standard cos-mological model. We use the same formalism to study the evolution of density perturbations in the universe. Authors show that a simple model like spherical collapse can be used to estimate the characteristics of halos of galaxies and clusters of galaxies.

1 illus, 6 ref

005002   Sujimol M R;Acharya R;Singh G;Gupta R K (NO, Delhi Earth Station, Space Applications Centre (SAC), ISRO, New Delhi-110 021, Email: sujimol@sac.isro.gov.in) : Rain attenuation using Ka and Ku and frequency beacons at Delhi earth station. Indian J Radio Space Phys 2015, 44(1), 45-50.

Quantitative analysis and prediction of radio signal attenuation is necessary in order to improve the reliability of satellite-earth communication links and for economically efficient design. The Ka band suffers large attenuation due to rain and as most of the parts of India are situated in the tropical region, the impact of rain on Ka band propagation is severe. None of the existing ITU-R models is validated for prediction of rain attenuation over India and only a few over the tropical region and hence, it calls for a propagation experiment to validate the existing models. In this paper, study on the effect of rain attenuation on the propagation of satellite signals in Ka band has been carried out by receiving signal of frequency 20.199 GHz from the IPSTAR (Thaicom-4 Satellite) and a Ku band beacon signal of frequency 11.698 GHz from GSAT-8 satellite at Delhi Earth Station of ISRO. It has been observed that the difference between the ITU-R predicted rain attenuations and the observed rain attenuations for Ka band varies from 1.5 to 4.5 dB and that for Ku band from 2.1 to 3.7 dB. The long-term probability distribution of fade slope for any definite base value of attenuation is symmetric on both positive and negative sides and this feature is independent of frequency. This observation corroborates earlier findings.

5 illus, 12 ref

003080   Punyakoti G V;Ramaseshan S (NO, , , Email: punyakoti.gv@gmail.com) : White dwarfs that crossed the chandrasekhar limit: can modified einstein's theory explain them?. Curr Sci 2015, 108(10), 1784-6.

4 illus, 15 ref

001085   Shylaja B S (NO, Jawaharlal Nehru Planetarium Sri T Chowdaiah Road High Grounds, Bengaluru-560 001, Email: shylaja.jnp@gmail.com) : From navigation to star hopping: forgotten formulae. Resonance 2015, 20(4), 352-9.

One of the great challenges faced by navigators of yesteryears was the calculation of distances when sailing in the sea. They made extensive use of trigonometry to help them in this endeavour. Trigonometry provided them with quicker, more accurate methods, and formulae, for determining distances. The same formulae found application in a totally different field - astronomy, for instance in finding the angular separation between stars or between planets and stars. What is amazing is the striking similarity between solutions developed by people from different locations, backgrounds and even times.

3 illus, 3 ref

001084   Rau A R P (Physics & Astronomy Dep, Louisiana State Univ, Baton Rouge 70803, USA, Email: arau@phys.isu.edu) : Rosetta-philae comet mission as physics appreciation. Resonance 2015, 20(4), 346-51.

This essay will show that with no more than simple school algebra and a willingness to wrestle with symbols and simple relations (equations) among them, anyone can appreciate further patterns beyond the purely visual. Far from any diminishing or 'taking away the poetry in Nature', this can only but add to our understanding and delight in the patterns that our senses have found striking.

2 illus, 2 ref

000051   Zhelyazkov I (Faculty of Physics, Sofia Univ, BG-1164 Sofia, Bulgaria, Email: izh@phys.uni-sofia.bg) : On modeling the kelvin-helmhotz instability in solar atmosphere. J Astrophys Astr 2015, 36(1), 233-54.

In the present review article, we discuss the recent developments in studying the Kelvin-Helmholtz (KH) instability of magne-tohydrodynamic (MHD) waves propagating in various solar magnetic structures. The main description is on the modeling of KH instability developing in the coronal mass ejections (CMEs), and contributes to the triggering of wave turbulence subsequently, leading to the coronal heating. KH instability of MHD waves in coronal active regions recently observed and imaged in unprecedented detail in EUV high cadence, high-resolution observations by SDO/AIA, and spectroscopic observations by Hinode/EIS instrument, is posing new challenge for its realistic modeling. It is shown that, considering the solar mass flows of CMEs as moving cylindrical twisted magnetic flux tubes, the observed instability can be explained in terms of unstable m = -3 MHD mode. Also describe the occurrence of the KH instability in solar jets. The obtained critical jet speeds for the instability onset, as well as the linear wave growth rates, are in good agreement with the observational data of solar jets.

5 illus, 165 ref

000050   Sindhuja G;Singh J (NO, Indian Insititute of Astrophysics, Koramangala, Bangalore-560 034, Email: sindhuja@iiap.res.in) : Temporal variation of Ca-K line profile of the sun during the solar cycle 22 and 23. J Astrophys Astr 2015, 36(1), 81-101.

Authors obtained the Ca-K line profile of the Sun as a star since 1969 at the Kodaikanal Observatory (KO) and analysis of the data showed the need to delineate the role of different chromospheric features to the variations of solar irradiance. We, therefore, initiated a new methodology to make observations of Ca-K line profiles of the Sun as a function of latitude and integrated over the longitude on a daily basis since 1986. We have collected the data for about thousand days, spread over two solar cycles. Earlier data (before 1997) were recorded on the photographic film and later data using the CCD detector. The photographic film data were digitized and analysed along with the data obtained from CCD camera. From these data, we computed K1 and K₂ widths for the Sun as a star, using all the observed line profiles as a function of latitude. In addition, we have analyzed the spectra of the whole Sun as a star obtained on some days and compared it with the results obtained from latitude spectra of the same day. The K₁ and K₂ widths of the Sun as a star derived from the KO data are compared with values determined from the observations made at other observatories to compare results from the new methodology of observations adopted by us and the earlier techniques. The average values of K1 width during the minimum period of solar cycle 23 are smaller than those during the minimum period of cycle 22. Day-to-day variations in the K1 and K2 widths and plage areas may imply that irradiance variations occur not only due to large-scale solar activity, but also because of variations in some of the three types of network in quiet regions of the Sun. The variation in intensity of the plages can also cause day-to-day variations in widths.

10 illus, 3 tables, 34 ref

000049   Pinter B (Solar System Research Group, Institute of Mathematics, Physics and Computer Science, Aberystwyth Univ, Aberystwyth, Penglais Campus, Physics Building, SY23 3BZ, Wales, UK, Email: b.pinter@aber.ac.uk) : Solar magnetic atmospheric effects on global helioseismic oscillations. J Astrophys Astr 2015, 36(1), 15-32.

Both the interior and the atmosphere of the Sun give a wide range of oscillations and waves. Interactions between waves and their highly structured and dynamic environment strongly influence the various properties of the waves. Understanding those possible interactions could provide priceless diagnostic tools in the search for hidden aspects of the solar interior and atmosphere. This article is an attempt to overview briefly our current understanding of how global helioseismic oscillations, f and p acoustic waves, interact with plasma flows and magnetic fields in the solar atmosphere.

2 illus, 96 ref