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You searched for subject:(solar spectral imaging). Showing records 1 – 2 of 2 total matches.

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Montana State University

1. Brannon, Sean Robert. Observations and modeling of plasma flows driven by solar flares.

Degree: PhD, College of Letters & Science, 2016, Montana State University

One of the fundamental statements that can be made about the solar atmosphere is that it is structured. This structuring is generally believed to be the result of both the arrangement of the magnetic field in the corona and the distribution of plasma along magnetic loops. The standard model of solar flares involves plasma transported into coronal loops via a process known as chromospheric evaporation, and the resulting evolution of the are loops is believed to be sensitive to the physical mechanism of energy input into the chromosphere by the are. We present here the results of three investigations into chromospheric plasma flows driven by solar are energy release and transport. First, we develop a 1-D hydrodynamic code to simulate the response of a simplified model chromosphere to energy input via thermal conduction from reconnection-driven shocks. We use the results from a set of simulations spanning a parameter space in both shock speed and chromospheric-to-coronal temperature ratio to infer power-law relationships between these quantities and observable evaporation properties. Second, we use imaging and spectral observations of a quasi-periodic oscillation of a are ribbon to determine the phase relationship between Doppler shifts of the ribbon plasma and the oscillation. The phase difference we find leads us to suggest an origin in a current sheet instability. Finally, we use imaging and spectral data of an on-disk are event and resulting are loop plasma flows to generally validate the standard picture of are loop evolution, including evaporation, cooling time, and draining downflows, and we use a simple free-fall model to produce the first direct comparison between observed and synthetic downflow spectra. Advisors/Committee Members: Chairperson, Graduate Committee: Dana W. Longcope (advisor), Dana Longcope was a co-author of the article, 'Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks' in the journal 'The astrophysical journal' which is contained within this thesis. (other), Dana W. Longcope and Jiong Qiu were co-authors of the article, 'Spectroscopic observations of evolving flare ribbon substructure suggesting origin in current sheet waves' in the journal 'The astrophysical journal' which is contained within this thesis. (other).

Subjects/Keywords: Solar flares; Solar chromosphere; Mathematical models; Spectral imaging

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APA (6th Edition):

Brannon, S. R. (2016). Observations and modeling of plasma flows driven by solar flares. (Doctoral Dissertation). Montana State University. Retrieved from https://scholarworks.montana.edu/xmlui/handle/1/9580

Chicago Manual of Style (16th Edition):

Brannon, Sean Robert. “Observations and modeling of plasma flows driven by solar flares.” 2016. Doctoral Dissertation, Montana State University. Accessed April 23, 2021. https://scholarworks.montana.edu/xmlui/handle/1/9580.

MLA Handbook (7th Edition):

Brannon, Sean Robert. “Observations and modeling of plasma flows driven by solar flares.” 2016. Web. 23 Apr 2021.

Vancouver:

Brannon SR. Observations and modeling of plasma flows driven by solar flares. [Internet] [Doctoral dissertation]. Montana State University; 2016. [cited 2021 Apr 23]. Available from: https://scholarworks.montana.edu/xmlui/handle/1/9580.

Council of Science Editors:

Brannon SR. Observations and modeling of plasma flows driven by solar flares. [Doctoral Dissertation]. Montana State University; 2016. Available from: https://scholarworks.montana.edu/xmlui/handle/1/9580


University of Illinois – Urbana-Champaign

2. Oktem, Sevinc. Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging.

Degree: PhD, 1200, 2014, University of Illinois – Urbana-Champaign

In this thesis, we develop a class of novel spectral imaging techniques that enable capabilities beyond the reach of conventional methods. Each development is based on computational imaging, which involves distributing the spectral imaging task between a physical and a computational system and then digitally forming images of interest from multiplexed measurements by means of solving an inverse problem. In particular, in the first approach, a nonscanning spectral imaging technique is developed to enable performing spectroscopy over a two-dimensional instantaneous field-of-view. This technique combines a parametric estimation approach with a slitless spectrometer configuration. In the second approach, a spectral imaging technique with an optical device known as a photon sieve is developed to achieve superior spatial and spectral resolutions relative to conventional filter-based spectral imagers. This technique relies on the wavelength-dependent focusing property of the photon sieve, and multiplexed measurements recorded by a photon sieve imaging system with a moving detector. In each of these two techniques, multiplexed measurements are combined with an image formation model and then the resultant inverse problem is solved computationally for image reconstruction. The associated inverse problems, which can be viewed as multiframe image deblurring problems, are formulated in a Bayesian estimation framework to incorporate the additional prior statistical knowledge of the targeted objects. Computationally efficient algorithms are then designed to solve the resulting nonlinear optimization problems. In addition to the development of each technique, Bayesian Cramer-Rao bounds are also obtained to characterize the estimation uncertainties and performance limits, as well as to explore the optimized system design. The effectiveness of the spectral imaging techniques are illustrated for an application in remote sensing of the solar atmosphere. Lastly, the phase retrieval problem, another inverse problem that arises in the photon-sieve imaging setting with coherent illumination, is studied to devise computationally efficient algorithms. As a whole, the developed spectral imaging techniques enable finer spectral information in the form of higher temporal, spatial, and spectral resolutions. This will enhance the unique diagnostic capabilities of conventional spectral imaging systems in applications as diverse as physics, chemistry, biology, medicine, astronomy and remote sensing. Advisors/Committee Members: Kamalabadi, Farzad (advisor), Kamalabadi, Farzad (Committee Chair), Blahut, Richard E. (Committee Chair), Bresler, Yoram (committee member), Davila, Joseph M. (committee member).

Subjects/Keywords: spectral imaging; imaging spectroscopy; computational imaging; inverse methods; maximum posterior estimation; Bayesian Cramer-Rao bounds; multiframe image deblurring; parameter estimation of superimposed signals; Phase retrieval; dynamic programming; instantaneous (non-scanning) spectral imaging; slitless spectrometer; photon sieve; image formation; diffractive imaging; space remote sensing; solar spectral imaging

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Oktem, S. (2014). Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/50384

Chicago Manual of Style (16th Edition):

Oktem, Sevinc. “Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed April 23, 2021. http://hdl.handle.net/2142/50384.

MLA Handbook (7th Edition):

Oktem, Sevinc. “Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging.” 2014. Web. 23 Apr 2021.

Vancouver:

Oktem S. Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Apr 23]. Available from: http://hdl.handle.net/2142/50384.

Council of Science Editors:

Oktem S. Computational imaging and inverse techniques for high-resolution and instantaneous spectral imaging. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/50384

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