Date of Award
Doctor of Philosophy in Applied Physics - (Ph.D.)
Federated Physics Department
Carsten J. Denker
Philip R. Goode
Dale E. Gary
This thesis includes the following sections: a general design of the Near Infrared Tunable Filter (NIRTF) of Advanced Technology Solar Telescope (ATST) project and the Near Infrared Imaging Magnetograph (IRIM) of the New Solar Telescope (NST), the design of achromatic waveplates, the narrowband continuum observation of a Sunspot at 1.56 µm using IRIM instruments, and the coronal hole observation using the Digital Vector Magnetograph (VMG) at Big Bear Solar Observatory (BBSO).
A near infrared tunable filter system is designed with detailed optical parameters for each component in the system. Among these components, the achromatic waveplates, which used to be an obstacle to the design of tunable filter systems, are redesigned using a Monte Carlo global optimization algorithm. The designs for three sets of such multi-layer achromatic waveplates are presented in the thesis. Experimental results are also obtained for three-layer quarter and half waveplates. These results show that the chromatism of waveplates is reduced to a satisfying level for the filter system in the wavelength range l000~1800 nm.
A set of narrow band continuum images at 1.56 µm are analyzed for the active region NOAA 10707 using the Lyot filter in the Near Infrared Imaging Magnetograph (IRIM) system and high order adaptive optics at National Solar Observatory (NSO), New Mexico. The analysis shows that the horizontal flow field within umbral region is small, in the order of 0.3 km.s-1 on average. Also, a narrow ring (370 km) within which the proper motion of the flow in the sunspot reverses its direction from inward to outward is identified. For the matured sunspot like the one in NOAA 10707, a gradual shrinking of spot is found, which suggests that at least in the early stage of the decay of matured active regions, a reduction of area takes place, instead of decomposing immediately.
A preliminary analysis of the magnetic flux data using the DVMG at BBSO reveals that, on the photospherical level, the magnetic flux evolves faster in quiet sun regions than in the coronal hole. Also fewer bipolar features are connected by arch filament (shown in Hα images) in the coronal hole. In the coronal hole, most of the closed magnetic loops appear at level lower than 5000 km, while open magnetic loops fill the space above 5000 km level. This observation suggests that flux cancellation or magnetic reconnection in photosphere and lower chromosphere may only take place at an atmospheric level lower than 5000 km, instead of the height where fast solar wind is believed to generate (between 5000~20000 km).
The science deduced based on these observations could be greatly improved by obtaining accurate measurements of the magnetic field strength (instead of flux density) and filling factor, which are the primary goals of the newly designed Near Infrared Tunable Filter system (NIRTF) in this thesis for the ATST and the New Solar Telescope (NST).
Ma, Jun, "Design and application of near infrared tunable filter for ATST and NST" (2007). Dissertations. 834.