Date of Completion

5-17-2016

Embargo Period

4-21-2016

Keywords

Comets, Pluto, Solar Wind, X-rays, Spectroscopy

Major Advisor

Dr. Vasili Kharchenko

Associate Advisor

Dr. Robin Cote

Associate Advisor

Dr. Phillip Mannheim

Field of Study

Physics

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

In order to establish contributions of different X-ray emission mechanisms from local astrophysical environments, we perform a theoretical analysis of observed cometary X-ray emission spectra. We develop a model from first principles that generates updated spectra of solar wind charge-exchange (CX) emissions together with accurate scattering and fluorescence spectra of solar X-rays by atoms, molecules, and dust/ice particles. This model also explores scattering and fluorescence spectra for different solar conditions, including spectra induced by solar X-ray flares of different classes and durations. We compare the modeled spectra with cometary and planetary observations from the Chandra X-Ray Observatory Advanced CCD Imaging Spectrometer (ACIS) and determine the primary emission mechanisms for both the 0.3–1.0 keV and 1.0–2.0 keV photon energy ranges. These comparisons establish upper limits on cometary dust/ice mass production rates and grain size distributions. Our results also demonstrate the utility of charge-exchange emissions as a remote diagnostics tool of both astrophysical plasma interaction and solar wind composition. In addition, we observe potential soft X-ray emissions via ACIS around 0.2 keV that are correlated in intensity to the hard X-ray emissions between 0.4-1.0 keV. We fit our CX model to these emissions, but our lack of a unique solution at low energies makes it impossible to conclude if they are cometary CX in origin. Finally, we discuss probable emission mechanism sources for these soft X-rays and explore new opportunities these findings present in understanding emission processes via Chandra.

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