March-2017 Seminar

Date : 28-03-2017
Time : 16:00:00
Speaker : Dr. Vikrant Jain
Associate Professor
Area : Geosciences Division
Venue : Ground Floor Lecture Hall

Abstract

Last two decades have witnessed major advancements in the quantitative understanding of geomorphological processes at different spatio-temporal scales. Modelling of geomorphic processes needs well defined geomorphic transport law(s) for different geomorphic systems. Studies in fluvial geomorphology has benefitted by a concept of stream power, which is a fundamental parameter to define driving force at any scale. It was incorporated in geomorphic studies from sixties through a study of sediment transport (Bagnold, 1966*). Subsequently, the stream power concept has been successfully applied to model various processes at different scales ranging from sand particle movement to landscape evolution processes. My talk will highlight the significance of unified concept in a geomorphic system, which led to integrate processes at different scales. The work will highlight new advancements and challenges in this research area. *Bagnold, R.A., 1966. An approach to the sediment transport problem from general physics. Geological Survey Professional Paper 422-I, I1– I37.

Date : 27-03-2017
Time : 16:00:00
Speaker : Dr. Rajkumar Hajra
Area : Space and Atmospheric Sciences Division
Venue : Ground Floor Lecture Hall

Abstract

The solar coronal holes emanate high-speed (~750-800 km s-1) streams (HSSs). If the coronal holes last for more than a solar rotation period (~27 days), the corresponding HSSs appear to “corotate” with the sun, very much like water spewing from a lawn sprinkler. These HSSs, when they interact with slow-speed (~300-400 km s-1) streams near the ecliptic plane, give rise to compressed plasma and magnetic field regions, the so-called corotating interaction regions (CIRs). The HSSs/CIRs are characterized by nonlinear interplanetary Alfvén waves. In the present talk I will show recent results on the CIR/HSS impacts on the near-Earth and cometary plasmas. The Earth’s magnetosphere and the cometary plasma without any intrinsic magnetic fields exhibit distinguishing interactions with the solar winds.Earth orbiting satellite and ground based observations will be presented to show the impacts on the Earth’s magnetosphere-ionosphere system.The solar wind impacts on the induced magnetosphere of the comet will be shown based on the observations made by the ESA’s Rosetta spacecraft that in situ monitored the target comet 67P/Churyumov-Gerasimenko for more than 2 years.

Date : 21-03-2017
Time : 16:00:00
Speaker : Ms. Rupa Mukherjee
Senior Research Fellow
Area : Geosciences Division
Venue : Ground Floor Lecture Hall

Abstract

Wetlands, lakes and lagoons play a central role in regional hydrologic and biogeochemical cycles, in maintaining biodiversity, and in a wide range of human activities. Chilika lagoon, the Asia's largest brackish water lagoon with estuarine character is a very important ecosystem in terms of ecology as well as economy. The talk will focus on the various ecological as well as environmental parameters of the lagoon which has been studied in 2004-2006 along with present understanding of the delta-13-C and delta-15-N isotopic signatures and N uptake rates.

Date : 17-03-2017
Time : 00:16:00
Speaker : Mr. Jabir M V
SRF
Area : Atomic, Molecular and Optical Physics
Venue : GF Lecture Hall

Abstract

Hybrid entangled states, having entanglement between different degrees-of-freedom (DoF) of a particle pair, are of great interest for quantum information science and communication protocols. Among different DoFs, the hybrid entangled states encoded with polarization and orbital angular momentum (OAM) allow the generation of qubit-qudit entangled states, macroscopic entanglement with very high quanta of OAM and improvement in angular resolution in remote sensing. Till date, such hybrid entangled states are generated by using a high-fidelity polarization entangled state and subsequent imprinting of chosen amount of OAM using suitable mode converters such as spatial light modulator in complicated experimental schemes. Given that the entangled sources have feeble number of photons, loss of photons during imprinting of OAM using diffractive optical elements limits the use of such hybrid state for practical applications. Here we report, on a simple experimental scheme to generate hybrid entangled state in polarization and OAM through direct transfer of classical non-separable state of the pump beam in parametric down conversion process. As a proof of principle, using local non-separable pump state of OAM mode l=3, we have produced quantum hybrid entangled state with entanglement witness parameter of = 1.25ą0.03 violating by 8 standard deviation. The generic scheme can be used to produce hybrid entangled state between two photons differing by any quantum number through proper choice of non-separable state of the pump beam.

Date : 16-03-2017
Time : 14:30:00
Speaker : Dr. Satyanarayan Mukhopadhyay
Area : Theoretical Physics
Venue : Room No. 469

Abstract

The energy, intensity and cosmic frontiers constitute the three major directions of research in particle physics, driven by a large number of ongoing and upcoming experimental and observational probes. Efforts to explore physics beyond the standard model at these experiments give rise to two challenging tasks : (1) how to dig out a tiny signal from a huge background using our understanding of known physics and (2) how to interpret the experimental results from a vast range of probes within an unified theoretical framework. I shall describe progress in addressing the first challenge using examples from the search for strongly interacting new particles at the LHC in difficult to access kinematic regimes. On the second challenge, I shall take up the case-study of classifying and understanding the different probes of particle dark matter, both within the framework of effective field theory as well as in specific simple models.

Date : 07-03-2017
Time : 16:00:00
Speaker : Dr. B. Maibam
Post Doctorol Fellow
Area : Geosciences Division
Venue : Ground Floor Lecture Hall

Abstract

The current understanding of the tectonic significance of blueschist-facies rocks associated with the Indo-Myanmar ophiolite belt is unclear due to a lack of systematic petrological study and the paucity of reliable age data. During the talk, I would present new integrated petrological and geochronological data for samples from the Nagaland complex of the Indo-Myanmar ophiolite belt, northeastern India, which constrains the pressure–temperature conditions and ages of peak and retrograde metamorphism

Date : 03-03-2017
Time : 16:00:00
Speaker : Dr. Anisetty S. K. A. V. Prasad Rao
Area : Space and Atmospheric Sciences Division
Venue : Ground Floor Lecture Hall

Abstract

Global Position System(GPS) soundings are assimilated to explore the impacts of GPS data on prediction of super Cyclone Gonu in 2007. Other data, including satellite data, radiosonde soundings and bogus vortex are also assimilated to highlight the relative contribution of GPS data to model prediction. Cyclone Gonu formed in the south central Arabian Sea and tracked west-northwestward into the Straights of Hormuz, reaching a peak intensity of 145 knots and a minimum sea-level pressure of 898 hPa before making a landfall in Iran. A series of experiments initialized with GPS refractivity from FORMOSAT-3/COSMIC (GPS), Special Sensor Microwave Imager (SSM/I) retrieved precipitable water and near-surface oceanic wind speed, GTS, QuickScatterometer (QuikSCAT) and bogus vortex are assessed by the model prediction using the advanced Weather Research and Forecasting (WRF) model with three dimensional variational data assimilation (3DVAR) to ingest these observations. Significant differences in cyclone track and intensity prediction are observed in various assimilations. GPS experiment outperforms other experiments in track prediction, while SSM/I improve intensity prediction. Sensitivity tests were conducted to identify which GPS soundings play a more important role in improvement of track prediction. It was found that the GPS soundings in the vicinity of Gonu vortex appear to modulate the environmental moistening conditions that lead to the impact on track prediction. Other sensitivity experiments show that retrieved GPS data information at upper levels greatly contributes to track prediction.

Date : 02-03-2017
Time : 16:00:00
Speaker : Ms. Aarthy E
Area : Astronomy & Astrophysics Division
Venue : Seminar Room # 113/114 (Thaltej Campus)

Abstract

Gamma Ray Bursts are the most powerful explosions observed so far in the universe since the Big Bang. Since the time it was discovered, over the past 4 decades the field of GRBs has grown tremendously with the advent of several missions like CGRO/BATSE, Swift, Fermi etc and other ground based observatories. Although, there are still unanswered questions related to the prompt emission (initial burst of gamma rays), the emission mechanism behind the inner most region of the relativistic jets. And measuring GRB Polarization could take this one step further. CZTI onboard AstroSat has an added advantage of being a GRB monitor and has capabilities to measure polarization at energies > 100 keV. I would brief about the current understanding of GRBs, how CZTI works as a polarimeter, and also would present the polarization results we have obtained for few GRBs using CZTI.