6 research outputs found
Acoustic Power Absorption and its Relation with Vector Magnetic Field of a Sunspot
The distribution of acoustic power over sunspots shows an enhanced absorption
near the umbra--penumbra boundary. Earlier studies revealed that the region of
enhanced absorption coincides with the region of strongest transverse potential
field. The aim of this paper is to (i) utilize the high-resolution vector
magnetograms derived using Hinode SOT/SP observations and study the
relationship between the vector magnetic field and power absorption and (ii)
study the variation of power absorption in sunspot penumbrae due to the
presence of spine-like radial structures. It is found that (i) both potential
and observed transverse fields peak at a similar radial distance from the
center of the sunspot, and (ii) the magnitude of the transverse field, derived
from Hinode observations, is much larger than the potential transverse field
derived from SOHO/MDI longitudinal field observations. In the penumbra, the
radial structures called spines (intra-spines) have stronger (weaker) field
strength and are more vertical (horizontal). The absorption of acoustic power
in the spine and intra-spine shows different behaviour with the absorption
being larger in the spine as compared to the intra-spine.Comment: 18 pages, 7 figures, In Press Solar Physics, Topical Issue on
Helio-and-Astroseismolog
Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode
The main objective of this paper is to build and compare vector magnetic maps
obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using
two inversion codes (UNNOFIT and MELANIE) based on the Milne-Eddington solar
atmosphere model. To this end, we used observations of a facular region within
active region NOAA 10996 on 23 May 2008, and found consistent results
concerning the field strength, azimuth and inclination distributions. Because
SOT/SP is free from the seeing effect and has better spatial resolution, we
were able to resolve small magnetic polarities with sizes of 1" to 2", and we
could detect strong horizontal magnetic fields, which converge or diverge in
negative or positive facular polarities. These findings support models which
suggest the existence of small vertical flux tube bundles in faculae. A new
method is proposed to get the relative formation heights of the multi-lines
observed by MTR assuming the validity of a flux tube model for the faculae. We
found that the Fe 1 6302.5 \AA line forms at a greater atmospheric height than
the Fe 1 5250.2 \AA line.Comment: 20 pages, 9 figures, 3 tables, accepted for publication in Solar
Physic
SPIN: an inversion code for the photospheric spectral line
Inversion codes are the most useful tools to infer the physical properties of the solar atmosphere from the interpretation of Stokes profiles. In this paper, we present the details of a new Stokes Profile INversion code (SPIN) developed specifically to invert the spectro-polarimetric data of the Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory. The SPIN code has adopted Milne–Eddington approximations to solve the polarized radiative transfer equation (RTE) and for the purpose of fitting a modified Levenberg–Marquardt algorithm has been employed. We describe the details and utilization of the SPIN code to invert the spectro-polarimetric data. We also present the details of tests performed to validate the inversion code by comparing the results from the other widely used inversion codes (VFISV and SIR). The inverted results of the SPIN code after its application to Hinode/SP data have been compared with the inverted results from other inversion codes.by Rahul Yadav, Shibu K. Mathew and Alok Ranjan Tiwar