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Browsing IIAP Publications by Subject "Magnetic fields"

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m-state Interference with Partial Frequency Redistribution for Polarized Line Formation in Arbitrary Magnetic Fields

Sampoorna, M (IOP Publishing, 2011-04-20)

The present paper concerns the derivation of polarized partial frequency redistribution (PRD) matrices for scattering on a two-level atom in arbitrary magnetic fields. We generalize the classical theory of PRD that is ...
Magnetic fields and young stellar objects in cometary cloud L1616

Saha, Piyali; Archana Soam; Baug, Tapas; Maheswar, G; Mondal, Soumen; Ghosh, Tuhin (Oxford University Press on behalf of Royal Astronomical Society, 2022-06)

The Lynds’ Dark Nebula (LDN) 1615/1616 and CB 28 (hereafter L1616) together form a cometary globule located at an angular distance of about 8◦ west of the Orion OB1 association, aligned roughly along the east–west direction, ...
Magnetic fields in cometary globules - II. CG 30-31 complex

Bhatt, H. C (The Royal Astronomical Society, 1999-09)

Optical linear polarization measurements of stars in the region of the cometary globules CG 30-31 in Vela-Puppis are presented. A polarization map representing the geometry of the magnetic field in the cometary globule ...
Magnetohydrostatic equilibrium in starspots: dependences on color (Teff) and surface gravity (g)

Rajaguru, S. P; Hasan, S. S (Cambridge University Press, 2011-08)

Temperature contrasts and magnetic field strengths of sunspot umbrae broadly follow the thermal-magnetic relationship obtained from magnetohydrostatic equilibrium. Using a compilation of recent observations, especially in ...
Maximum acceleration and magnetic field in the early universe

Sivaram, C; de Sabbata, Venzo (Kluwer Academic Publishers, 1991-02)

The maximum acceleration at the Planck epoch is shown to be related to the maximum magnetic field and curvature as well as temperature in that era. Spin-torsion effects at that epoch also lead to same value.
Models of Flux Tubes from Constrained Relaxation

Mangalam, A; Krishan, V (Indian Academy of Sciences, 2000-12)

We study the relaxation of a compressible plasma to an equilibrium with flow. The constraints of conservation of mass, energy, angular momentum, cross-helicity and relative magnetic helicity are imposed. Equilibria ...
Multi-dimensional Radiative Transfer to Analyze Hanle Effect in Ca II K Line at 3933 Å

Anusha, L. S; Nagendra, K. N (IOP Publishing, 2013-04-20)

Radiative transfer (RT) studies of the linearly polarized spectrum of the Sun (the second solar spectrum) have generally focused on line formation, with an aim to understand the vertical structure of the solar atmosphere ...
Observations of the forward scattering Hanle effect in the Ca I 4227 Å line

Bianda, M; Ramelli, R; Anusha, L. S; Stenflo, J. O; Nagendra, K. N; Holzreuter, R; Sampoorna, M; Frisch, H; Smitha, H. N (EDP Sciences, 2011-06)

Chromospheric magnetic fields are notoriously difficult to measure. The chromospheric lines are broad, while the fields are producing a minuscule Zeeman-effect polarization. A promising diagnostic alternative is provided ...
On the Large-Scale Diffuse Magnetic Field of the Sun

Dikpati, M; Choudhuri, A. R (Springer, 1995-10)

Although the sunspots migrate towards the equator, the large-scale weak diffuse magnetic fields of the Sun migrate poleward with the solar cycle, the polar field reversing at the time of the sunspot maxima. We apply the ...
Peculiarities in the ionic tail of Comet Ikeya-Seki (1965f)

Krishan, V; Sivaraman, K. R (D. Reidel Publishing Co., 1982-04)

Direct photographs of Comet Ikeya-Seki obtained on four consecutive days from October 29 to November 1, 1965, are used for an analysis of the multiple helical structures in the ionised tail. The formation of these structures ...
Periodic and Quasi-Periodic Variations in the Ca K Index During the 20th Century Using Kodaikanal Data

Priyal, Muthu; Singh, J; Ravindra, B; Chandar Shekar, B (Springer, 2019-09)

We have digitized the Ca K images obtained at Kodaikanal Observatory with a pixel resolution of 0.86 arcsec and 16-bit readout to achieve better spatial and photometric accuracy. In addition to the general photometric ...
Polar Network Index as a Magnetic Proxy for the Solar Cycle Studies

Priyal, M; Banerjee, D; Karak, B. B; Munoz-Jaramillo, A; Ravindra, B; Choudhuri, A. R; Singh, J (IOP Publishing, 2014-09-20)

The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot ...
Polarimetric and photometric investigation of the dark globule LDN 1225: distance, extinction law, and magnetic fields

Eswaraiah, C; Lai, Shih-Ping; Ma, Yuehui; Anil K. Pandey; Jose, J; Chen, Zhiwei; Samal, M. R; Wang, Jia-Wei; Sharma, S; Ojha, D. K (IOP Publishing, 2019-04-10)

We present results based on the optical R-band observations of the polarization of 280 stars distributed toward the dark globule LDN 1225. Parallaxes from Gaia data release 2 along with the polarization data of ~200 stars ...
Polarization Maps for the Dark Clouds B:227 and L:121

Bhatt, H. C; Jain, S. K (European Southern Observatory, 1993-09)

Optical linear polarization measurements for stars in the regions of the molecular clouds B 227 and L 121 are presented. The magnetic field geometry in the clouds as indicated by the polarization maps is discussed in ...
Polarized Light Scattering with the Paschen-Back Effect, Level-crossing of Fine Structure States, and Partial Frequency Redistribution

Sowmya, K; Nagendra, K. N; Sampoorna, M; Stenflo, J. O (IOP Publishing, 2014-10-01)

The quantum interference between the fine structure states of an atom modifies the shapes of the emergent Stokes profiles in the second solar spectrum. This phenomenon has been studied in great detail both in the presence ...
Polarized Line Formation in Multi-dimensional Media. III. Hanle Effect with Partial Frequency Redistribution

Anusha, L. S; Nagendra, K. N (IOP Publishing, 2011-09-01)

In two previous papers, we solved the polarized radiative transfer (RT) equation in multi-dimensional (multi-D) geometries with partial frequency redistribution as the scattering mechanism. We assumed Rayleigh scattering ...
Polarized Line Formation in Multi-dimensional Media. IV. A Fourier Decomposition Technique to Formulate the Transfer Equation with Angle-dependent Partial Frequency Redistribution

Anusha, L. S; Nagendra, K. N (IOP Publishing, 2011-09-20)

To explain the linear polarization observed in spatially resolved structures in the solar atmosphere, the solution of polarized radiative transfer (RT) equation in multi-dimensional (multi-D) geometries is essential. For ...
Polarized Line Formation in Multi-dimensional Media. V. Effects of Angle-dependent Partial Frequency Redistribution

Anusha, L. S; Nagendra, K. N (IOP Publishing, 2012-02-10)

The solution of polarized radiative transfer equation with angle-dependent (AD) partial frequency redistribution (PRD) is a challenging problem. Modeling the observed, linearly polarized strong resonance lines in the solar ...
Polarized line formation with J-state interference in the presence of magnetic fields: A Heuristic treatment of collisional frequency redistribution

Smitha, H. N; Nagendra, K. N; Sampoorna, M; Stenflo, J. O (Elsevier B.V., 2013-01)

An expression for the partial frequency redistribution (PRD) matrix for line scattering in a two-term atom, which includes the J-state interference between its fine structure line components is derived. The influence of ...
Polarized Scattering with Paschen-Back Effect, Hyperfine Structure, and Partial Frequency Redistribution in Magnetized Stellar Atmospheres

Sowmya, K; Nagendra, K. N; Stenflo, J. O; Sampoorna, M (IOP Publishing, 2014-05-10)

F-state interference significantly modifies the polarization produced by scattering processes in the solar atmosphere. Its signature in the emergent Stokes spectrum in the absence of magnetic fields is depolarization in ...

Browsing IIAP Publications by Subject "Magnetic fields"

Browsing IIAP Publications by Subject "Magnetic fields"

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