Application of adaptive optics to the spectroscopic investigation of small-scale solar structures

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.

Name thesis:degree_name

Doctor of Philosophy in Applied Physics - (Ph.D.)

Discipline thesis:degree_discipline

Federated Physics Department

Year

2003

Author dc:creator

• Hartkorn, Klaus

Contributors dc:contributor

• Ken K. Chin
• Carsten J. Denker
• Dale E. Gary

• sun
• photosphere
• bright points
• g-band
• sunspot
• umbral dots
• Other Physics

Repository record dc:identifier

https://digitalcommons.njit.edu/dissertations/576

OAI identifier oai:identifier

oai:digitalcommons.njit.edu:dissertations-1631