Discriminant analysis of solar bright points and faculae II. Contrast and morphology analysis

Taken at a high spatial resolution of 0.1 arcsec, Bright Points (BPs) are found to coexist with faculae in images and the latter are often resolved as adjacent striations. Understanding the properties of these different features is fundamental to carrying out proxy magnetometry. To shed light on the relationship between BPs and faculae, we studied them separately after the application of a classification method, developed and described in a previous paper) on active region images at various heliocentric angles. In this Paper, we explore different aspects of the photometric properties of BPs and faculae, namely their G-band contrast profiles, their peak contrast in G-band and continuum, as well as morphological parameters. We find that: (1) the width of the contrast profiles of the classified BPs and faculae are consistent with studies of disk center BPs at and limb faculae, which indirectly confirms the validity of our classification, (2) the profiles of limb faculae are limbward skewed on average, while near disk center they exhibit both centerward and limbward skewnesses due to the distribution of orientations of the faculae, (3) the relation between the peak contrasts of BPs and faculae and their apparent area discloses a trend reminiscent of magnetogram studies. The skewness of facular profiles provides a novel constraint for 3D MHD models of faculae. As suggested by the asymmetry and orientation of their contrast profiles, faculae near disk center could be induced by inclined fields, while apparent BPs near the limb seem to be in fact small faculae misidentified. The apparent area of BPs and faculae could be possibly exploited for proxy magnetometry

Magnetohydrostatic equilibrium in starspots: dependences on color (T_{eff}) and surface gravity (g)

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 molecular bands, of temperature contrasts of starspots in cool stars, and a grid of Kurucz stellar model atmospheres constructed to cover layers of sub-surface convection zone, we examine how the above relationship scales with effective temperature T_{eff}, surface gravity g and the associated changes in opacity of stellar photospheric gas. We calculate expected field strengths in starpots and find that a given relative reduction in temperatures (or the same darkness contrasts) yield increasing field strengths against decreasing T_{eff} due to a combination of pressure and opacity variations against T_{eff}.Comment: 4 pages, 3 figures, to appear in the Proceedings of IAUS 273: "Physics of Sun and Star Spots", eds. D.P. Choudhary and K. Strassmeier 2010, Cambridge University Pres

"માછીમારોના વ્યક્તિત્વ લક્ષણો, મનોવૈજ્ઞાનિક સુખાકારી અને વ્યવસાય સામેલગીરીનો મનોવૈજ્ઞાનિક અભ્યાસ"

Not Availabl

Gravity-induced birefringence within the framework of Poincare gauge theory

Gauge theories of gravity provide an elegant and promising extension of general relativity. In this paper we show that the Poincar\'e gauge theory exhibits gravity-induced birefringence under the assumption of a specific gauge invariant nonminimal coupling between torsion and Maxwell's field. Furthermore we give for the first time an explicit expression for the induced phaseshift between two orthogonal polarization modes within the Poincar\'e framework. Since such a phaseshift can lead to a depolarization of light emitted from an extended source this effect is, in principle, observable. We use white dwarf polarimetric data to constrain the essential coupling constant responsible for this effect.Comment: 12 pages, accepted for publication by Physical Review

"સંરક્ષણ કર્મચારીઓમાં વ્યવસાયિક મનોભાર, વ્યવસાયિક સંતોષ અને માનસિક સ્વાસ્થ્યનો મનોવૈજ્ઞાનિક અભ્યાસ"

માનવજીવન દિન-પ્રતિદિન વધુને વધુ જટિલ બનતું જાય છે. આધુનિક સમાજમાં બની રહેલી ઘટનાઓ બુધ્ધિજીવી માણસને વિચાર કરતો મૂકે છે કે ખરેખર માણસ સુખી બન્યો છે કે દુઃખની ગર્તામાં ધકેલાયો છે? ભારતમાં અને વિશ્ર્વમાં આતંકવાદ ફેલાતો જાય છે અને રોજ અનેક નિર્દોષ માણસોની કર

Globalisation and its Impacts on Indian Economy

Not availabl

CSM-428: Techniques used for Location-based Services: A Survey

Not availabl

Modified p-modes in penumbral filaments?

Aims: The primary objective of this study is to search for and identify wave modes within a sunspot penumbra. Methods: Infrared spectropolarimetric time series data are inverted using a model comprising two atmospheric components in each spatial pixel. Fourier phase difference analysis is performed on the line-of-sight velocities retrieved from both components to determine time delays between the velocity signals. In addition, the vertical separation between the signals in the two components is calculated from the Stokes velocity response functions. Results: The inversion yields two atmospheric components, one permeated by a nearly horizontal magnetic field, the other with a less-inclined magnetic field. Time delays between the oscillations in the two components in the frequency range 2.5-4.5 mHz are combined with speeds of atmospheric wave modes to determine wave travel distances. These are compared to expected path lengths obtained from response functions of the observed spectral lines in the different atmospheric components. Fast-mode (i.e., modified p-mode) waves exhibit the best agreement with the observations when propagating toward the sunspot at an angle ~50 degrees to the vertical.Comment: 8 pages, 12 figures, accepted for publication in Astronomy & Astrophysic