http://hdl.handle.net/2248/66 Ph.D. Theses with IIAP affiliation are submitted here Search the Channel search http://prints.iiap.res.in/simple-search http://hdl.handle.net/2248/6019 Title: Study of Li-rich K Giants<br/><br/>Authors: Bharat Kumar, Y<br/><br/>Description: Thesis Supervisor Dr. B. Eswar Reddy http://hdl.handle.net/2248/6005 Title: On the Nature of Propagating MHD Wavesin the Solar Atmosphere<br/><br/>Authors: Girjesh R. Gupta<br/><br/>Description: Thesis Supervisor Prof. Dipankar Banerjee http://hdl.handle.net/2248/6004 Title: Advanced Numerical Methods for Polarized Line Formation Theory<br/><br/>Authors: Anusha, L. S<br/><br/>Abstract: This thesis aims to develop methods to solve radiative transfer (RT) problems in severalastrophysical contexts. A major part of the thesis is devoted to develop an understandingof the effects of multi- dimensional (multi-D) RT on the polarized line formation. Weconsider partial frequency redistribution (PRD) of line radiation in the presence/absenceof external magnetic fields. The thesis consists of three parts. In the first part we developmodern numerical methods to solve the line RT equation in one-dimensional (1D) planarand spherical media. In the second part, we formulate and solve the problem of polarizedline RT equation in multi-D media. In the third part we focus our attention on realisticmodeling of the spectro-polarimetric observations of the linearly polarized spectrum of theSun (the well known second solar spectrum).<br/><br/>Description: Thesis Supervisor Prof. K. N. Nagendra http://hdl.handle.net/2248/5953 Title: A Pc-scale study of radio-loud AGN : The Fanaroff–Riley Divide and Unification<br/><br/>Authors: Preeti Kharb<br/><br/>Abstract: In this thesis an attempt is made to address the Fanaroff-Riley (FR) dichotomyobserved in radio-powerful active galactic nuclei (AGNs) within the framework of the“Unification Scheme” for radio-loud AGNs, using high angular resolution total intensityand polarization observations in the radio and optical wavebands. We describe thetechnique of Very Long Baseline Interferometry (VLBI) and VLBI polarimetry (VLBP)which were made use of in order to study the magnetic (B) field structure and orientationin AGN jets on parsec-scales. In this thesis we present the first VLBP images of fourrelatively low-luminosity FRI radio galaxies with detected polarized emission on parsecscales.We further present the results from our multi-frequency, multi-epoch VLBPobservations of the broad-line FRII radio galaxy – 3C111. We compare and contrast ourVLBP results in the light of the Fanaroff-Riley dichotomy and the Unified Scheme thatrelates the FRI and FRII radio galaxies to BL Lac objects and quasars, respectively. Wefind that the B-field geometry in FRIs and FRII(s) is similar to radio-powerful BL Lacsand quasars respectively, in accordance with the Unified Scheme. We present VLBPimages of the relatively poorly studied subclass of BL Lacertae objects, the high-energypeaked BL Lacs (HBLs). We find that they tend to exhibit a predominantly longitudinalB-field geometry in their VLBI jets, similar to the radio-loud quasars but different fromthe low-energy peaked BL Lacs (LBLs) which show a predominantly transverse B-fieldgeometry in their jets. We examine the nature of the unresolved optical nuclei discoveredby the Hubble Space Telescope in the centres of a majority of FR radio galaxies by fittingsimple models to the optical and radio data. We conclude that the nature of the opticalnuclei in the FRI population (FRI radio galaxies and BL Lac objects) and the FRIIpopulation (FRII radio galaxies and radio-loud quasars) differs in a significant manner.FRI sources probably lack the optically thick obscuring tori around their central engineswhile FRII sources do not. Further, the contribution to the nuclear optical luminosityfrom the accretion disk is much more significant in the FRII population.xx