Physics Commons^™

New Facet Of Solar Activities Revealed By High-Resolution Imaging At He I 10830 Å, Zhicheng Zeng

Dissertations

Major solar activities such as major flares and associated coronal mass ejections (CMEs), have a great impact on space weather, which requires us to develop the ability to predict them. Despite the extensive studies already made, however, many basic processes, such as energy accumulation processes in solar active regions and the triggering mechanism of solar activities, are still not well understood.

One reason why the basic processes are hard to be understood is that the large-scale activities are complicated, involving many small-scale energy releases, making it hard to understand the basic picture of the events. Small-scale solar activities, such as …

Stellar Spectroscopy: New Methods And Insights, Sanaz S. Golriz

Electronic Thesis and Dissertation Repository

The study of the chemical evolution of stars is of crucial importance since they play a major role in the enrichment of the chemistry of the universe. Throughout their lifetime, stars undergo several processes that can alter their chemistry. Gradually, the nucleosynthesis products from the interior of the star are radiatively and convectively levitated and mixed with the upper layers of the atmosphere. In the later stages of their evolution, low to intermediate mass stars (0.8-8.0~M☉) eject a significant fraction of these nucleosynthesis products, resulting in a circumstellar envelope of gas and dust around the central star with a very …

Probing The Complex Magnetic, Electronic And Structural Properties In Correlated Manganese Oxides, Peng Gao

Dissertations

Rare-earth Manganese Oxides (RMnO₃) exhibit two distinct structural phases: the orthorhombic structure and the hexagonal structure. The doped orthorhombic phase exhibits a metal to insulator transition, charge ordering and a strong response of electron transport properties to magnetic fields (colossal magneto-resistance). At low temperatures, this system may also exhibit a finite polarization which couples to external magnetic fields. The hexagonal phase is known to have a large spontaneous polarization at high temperatures which couples to the low temperature magnetic order. These materials are important from the basic point of view of understanding strong electronic correlations and …

Studies Of Solar White-Light Flares And Small-Scale Magnetic Structures Observed In The Near Infrared, Yan Xu

Dissertations

Using the most advanced infrared imaging technology as developed by NJIT, detailed study of solar white-light flares and small magnetic structures, such as faculae and pores, are presented in this dissertation. The investigations focus on near-infrared observations at 1.56 μm, which are good proxy of the deepest layer of the solar photosphere.

I made fundamental contributions in two areas of near infrared (NIR) solar physics: (1) the first detection and understanding of white-light flares in the NIR and (2) clearly demonstrated non-existence of "dark faculae". Several high-resolution observations have been carried out at BBSO and National Solar Observatory/Sacramento Peak. The …

Resonances Of Periodic Metal-Dielectric Structures At The Infrared Wavelength Region, Oren Sternberg

Dissertations

Metal meshes have been used as reflectors in radar receivers for wavelength much longer than the periodic constant of the conducting wires and as optical reflectors in a FabryPerot in the far infrared. Cross shaped metal meshes can be used as band pass filters but the design theory and near field properties have not been known.

Transmittance of thin, single-layer and multiplayer metal meshes has been investigated using Micro-Strips, yielding numerical solutions of Maxwell's equations. The near field effect was studied for two alignment configurations of cross shaped metal meshes, both free standing and with dielectrics, and transmission line theory …