The New Jersey Institute of Technology's
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Title:	Application of adaptive optics to the spectroscopic investigation of small-scale solar structures
Author:	Hartkorn, Klaus
View Online:	njit-etd2003-073 (xxix, 194 pages ~ 20.4 MB pdf)
Department:	Federated Physics Department of NJIT and Rutgers-Newark
Degree:	Doctor of Philosophy
Program:	Applied Physics
Document Type:	Dissertation
Advisory Committee:	Chin, Ken K. (Committee member) Denker, Carsten J. (Committee member) Gary, Dale E. (Committee member) Goode, Philip R. (Committee member) Rimmele, T. R. (Committee chair) Wang, Haimin (Committee member) Wu, Zhen (Committee member)
Date:	2003-05
Keywords:	sun photosphere bright points g-band sunspot umbral dots
Availability:	Unrestricted
Abstract:	We study bright points, umbral dots and the G-band using a two-dimensional spectrometer and an Adaptive Optics system, which allows us to record high-resolution dopplergrams and residual intensity images. We find evidence that bright points are smaller than 120 km in diameter. Bright points are situated exclusively in regions of enhanced G-band brightness and do not show a change in their shape or a displacement in their position of more than 120 km horizontally over a height range from 0 km to 320 km above photospheric level T = 1. We do not find velocity differences of more than 100 m/s and a size of 120 km at the locations of bright points compared to the surroundings. Bright points have a higher contrast in the G-band as well as in the atomic spectral lines. We suspect the existence of two contrast enhancement mechanisms for bright points one exclusively for the G-band, one independent of specific spectral lines. We perform calculations using the results of a three-dimensional magneto-hydrodynamical model as input for a radiative transfer calculation, but find little agreement with our observations. The core intensity of the G-band CH lines is significantly influenced by the atmospheric conditions in heights of 160 km and 320 km, but not heights of 40 km. The velocity investigation of a sunspot shows that umbral dots seem to consist of two different types. The first type is the bright part of an intensity pattern of 1000-2000 km size with a corresponding negatively correlated velocity pattern which is probably related to umbral oscillations. The second type consists of localized brightening of a size of not more than 300 km that are associated with down-flowing plasma. Furthermore, we find penumbral grains that have penetrated the umbra and appear as brightenings. We study the velocity signature of penumbral grains and find strong up-flows of solar plasma associated with the inner, bright parts of penumbral grains, where as the general correlation between intensity and velocity within the penumbra is weak.