Oo, Yee Yee, San, Phyu Phyu, Sampoorna, M., Nagendra, K. N., Ramachandran, G.
Using a quantum electrodynamical approach, we derive the scattering phase matrices for polarized radiation involving forbidden line transitions and in the presence of an external magnetic field. The...
Some aspects of polarized line formation in magneto-turbulent media (2008)
Sampoorna, M, Frisch, H, Nagendra, K. N
Observations and numerical simulations of magneto-convection show a highly variable solar magnetic field. Using a statistical approach, we analyze the effects of random magnetic fields on Stokes...
Sampoorna, M, Nagendra, K. N, Stenflo, J. O
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Scattering polarization in the presence of magnetic and electric fields (2007)
Yee Yee Oo, Sampoorna, M, Nagendra, K. N, Ananthamurthy, S, Ramachandran, G
The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under...
Hanle-Zeeman Redistribution Matrix. I. Classical Theory Expressions in the Laboratory Frame (2007)
Sampoorna, M, Nagendra, K. N, Stenflo, J. O
Polarized scattering in spectral lines is governed by a 4×4 matrix that describes how the Stokes vector is scattered and redistributed in frequency and direction. Here we develop the theory for this...
Generalized Voigt functions and their derivatives (2007)
Sampoorna, M, Nagendra, K. N, Frisch, H
This paper deals with a special class of functions called generalized Voigt functions H(n)(x,a) and G(n)(x,a) and their partial derivatives, which are useful in the theory of polarized spectral line...
Scattering Polarization in the Presence of Magnetic and Electric Fields (2007)
Oo, Yee Yee, Sampoorna, M., Nagendra, K. N., Ananthamurthy, Sharath, Ramachandran, G.
The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under...
Scattering Polarization in the Presence of Magnetic and Electric Fields (2007)
Oo, Yee Yee, Sampoorna, M, Nagendra, K. N, Ananthamurthy, S, Ramachandran, G
The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under...
Stochastic polarized line formation. II. Zeeman line transfer in a random magnetic field (2006)
Frisch, H, Sampoorna, M, Nagendra, K. N
Context.The Zeeman effect produced by a turbulent magnetic field or a random distribution of flux tubes is usually treated in the microturbulent or macroturbulent limits where the Zeeman propagation...
Stochastic polarized line formation I. Zeeman propagation matrix in a random magnetic field (2005)
Frisch, H, Sampoorna, M, Nagendra, K N
This paper considers the effect of a random magnetic field on Zeeman line transfer, assuming that the scales of fluctuations of the random field are much smaller than photon mean free paths...
Scattering of Polarized Radiation by Atoms in Magnetic and Electric Fields (2005)
Oo, Yee Yee, Nagendra, K. N., Ananthamurthy, Sharath, Ramachandran, G.
The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Analytic formulae are derived for the...
Yee Yee Oo, Nagendra, K. N, Ananthamurthy, S, Sirsi, S, Vijayashanka, R, Ramachandran, G
In continuation of our earlier investigation (referred to hereafter as part I) where we considered the mathematically simple case of magnetic field orientation along the Z-axis of the principal axes...
Stochastic polarized line formation: I Zeeman propagation matrix in a random magnetic field (2005)
Frisch, H, Sampoorna, M, Nagendra, K. N
This paper considers the effect of a random magnetic field on Zeeman line transfer, assuming that the scales of fluctuations of the random field are much smaller than photon mean free paths...
Stochastic polarized line formation I. Zeeman propagation matrix in a random magnetic field (2005)
Frisch, H, Sampoorna, M, Nagendra, K N
This paper considers the effect of a random magnetic field on Zeeman line transfer, assuming that the scales of fluctuations of the random field are much smaller than photon mean free paths...
Yee Yee Oo, Nagendra, K. N, Ananthamurthy, S, Vijayashankar, R, Ramachandran, G
The polarization of emission lines formed in a medium immersed in external electric and magnetic fields is studied. The electric field is assumed to be quadrupolar in nature, while the magnetic field...
Nagendra, K. N, Frisch, H, Fluri, D. M
In this paper we present brief review on Polarized Approximate Lamda Iteration (PALI) line radiative transfer method, for solving the Hanle effect line formation problem with Angle Averaged (AA)...
Fluri, D. M, Nagendra, K. N, Frisch, H
A generalized iteration method is presented to solve the polarized line transfer equation for a two-level-atom in an arbitrarily oriented, weak magnetic field. The polarized redistribution matrix...
Numerical Solutions of Polarized Line Transfer Equations (2003)
Recent developments in the NLTE polarized line formation theory in Astrophysics is discussed. Attention is focussed on pure theoretical aspects of the problem. A conventional method of solving the...
Some Equations of Discrete Space Method (DSM) for Polarized Line Transfer (2003)
In this note, we present few equations of the Discrete Space Method (DSM) for polarized line transfer. These equations are presented as extensions to the main paper entitled Numerical Solutions of...
Hanle effect with angle-dependent partial redistribution (2002)
Nagendra, K. N, Frisch, H, Faurobert, M
The polarized line transfer equation for the Hanle effect is solved in the framework of an exact partial frequency redistribution (PRD) theory developed by Bommier (1997a,b). In that theory the...
The Hanle Effect with Angle Dependent Redistribution Functions (2001)
Frisch, H, Faurobert, M, Nagendra, K. N
Numerical work with the Hanle effect, taking into account Partial frequency Redistribution (PRD) effects has so far been studied with the approximation that frequency redistribution can be described...
Nagendra, K. N, Faurobert, H, Faurobeet-Scholl, M, Paletou, F
We present an application of the PALI (Polarized Approximate Lambda Iteration) method to the resonance scattering in spectral lines formed in the presence of weak magnetic fields. The method is based...
Fast Numerical Methods for Polarized Line Radiative Transfer in the Presence of Hanle Effect (1999)
Faurobert, M, Frisch, H, Nagendra, K. N
The Hanle effect provides a diagnostic tool for weak magnetic fields which do not give rise to a measurable Zeeman effect, such as turbulent fields or magnetic canopies. The lines which are sensitive...
Nagendra, K. N, Frisch, H, Faurobert-Scholl, M
In this paper we present an Approximate Lambda Iteration method to treat the Hanle effect (resonance scattering in the presence of a weak magnetic field) for lines formed with complete frequency...
Nagendra, K. N, Frisch, H, Faurobert-Scholl, M
In this paper we present an Approximate Lambda Iteration method to treat the Hanle effect (resonance scattering in the presence of a weak magnetic field) for lines formed with complete frequency...
Faurobert-Scholl, M, Frisch, H, Nagendra, K. N
In this paper we generalize an Approximate Lambda Iteration (ALI) technique developed for scalar transfer problems to a vectorial transfer problem for polarized radiation. Scalar ALI techniques are...
Faurobert-Scholl, M, Frisch, H, Nagendra, K. N
In this paper we generalize an Approximate Lambda Iteration (ALI) technique developed for scalar transfer problems to a vectorial transfer problem for polarized radiation. Scalar ALI techniques are...
Green's matrix for Compton reflection of polarized radiation from cold matter (1996)
Poutanen, J, Nagendra, K. N, Svensson, R
The Compton-reflected spectrum from cold matter for incident X-rays and gamma-rays with arbitrary angular, spectral and polarization properties can be determined by a simple folding of Green's matrix...
Models of highly extended dust shells around R Coronae Borealis (1996)
Radiation transport models are constructed for the dust shells of the hydrogen deficient supergiant star R Coronae Borealis (R CrB). IRAS observations of R CrB are used as constraints in selecting...
Partial redistribution effects on line polarization in the presence of velocity fields (1996)
Velocity fields in line formation regions strongly affect the line polarization. The conventionally used observer's frame method of solving the polarized transfer equation becomes expensive and...
Collisional redistribution effects on line polarization in spherical atmospheres (1995)
The polarization of resonance and subordinate lines formed in spherically symmetric media is studied. The effect of collisions is shown by taking a combination of partial redistribution mechanisms...
The problem of resonance line polarization including collisional redistribution is studied using simple theoretical models. The medium is assumed to be a static finite spherical shell atmosphere. The...
Nagendra, K. N, Rangarajan, K. E, Rao, D. M
The combined effect of partial frequency redistribution by atoms (PRD) and noncoherent electron scattering (NCES) on line formation is studied, taking account of the polarization state of the...
Polarization of resonance lines formed in extended spherical atmospheres (1989)
The present consideration of the polarization problem posed by resonance lines in extended spherical atmospheres assumes that the atmosphere in question is at rest and emphasizes the determination of...
Resonance line polarization in spherical atmospheres (1988)
The basic features of the resonance line polarization in spherically symmetric media are examined using simple physical and atmospheric models, with special consideration given to the two-level atom...
Some physical processes influencing the polarization of continuum and line radiation (1987)
Some physical mechanisms which affect the continuum and line polarization are studied. The physical conditions of the plasma selected for this purpose represent different astrophysical situations of...
Polarization line radiative transfer in the atmospheres of magnetic white dwarfs (1987)
Some physical mechanisms which can affect the Zeeman line profiles of magnetic white dwarfs are studied. The pure absorption polarization transfer equation is solved including these mechanisms. The...
Some aspects of the solution of vector transfer equation in a magnetized medium (1985)
A simplification of the numerical method of solving the vector transfer equation, given earlier by Nagendra and Peraiah (1985), is described for problems which involve only absorption. This makes it...
Numerical solution of the radiative transfer equation in a magnetized medium (1985)
A numerical method of solution based on the discrete space theory of radiative transfer as applied to the transfer problems in an anisotropic medium is discussed. Two simple applications, namely the...
Polarization of continuum radiation in magnetic atmospheres (1984)
A numerical solution is presented for the problem of continuum radiative transfer in a magnetoactive medium. The continuum opacities are calculated in the presence of a strong magnetic field (H = 10...
Simultaneous solutions of the radiative transfer equation in the comoving frame and the statistical equilibrium equation, for a non-LTE two-level atom, have been obtained by means of angle-averaged...
Peraiah, A, Raghunath, G, Nagendra, K. N
The effect of high optical depths and large rotational velocities on the spectral lines in rotating and radial expanding spherical shells is investigated. It is assumed that the outer radius of the...
Lines Formed in Slowly Expanding Thin Spherical Shell (1980)
Peraiah, A, Raghunath, G, Nagendra, K. N
We have investigated how an optically thin spherical shell with small velocities change the profiles and equivalent widths of the lines. We have employed several types of variations in density,...