The goal of laser astrophysics is to provide a means by which aspects of specific astrophysical phenomena can be reproduced in the laboratory. Although the hydrodynamic instabilities of early supernova remnants have already been studied using this method, the role of significant radiative losses in shock propagation (for example, in late-term remnants) has only been imperfectly modeled. This thesis introduces an improved self-similar analytic approach to radiative blast-wave evolution where the total amount of energy loss remains constant in proportion to the energy flux entering the shock front. The approximation is solved for the cases in which both energy loss from the shock front and heating of the shock (due to the presence of ionization precursors) are significant. Because this solution is independent of the exact method of cooling, it is appropriate for both the laboratory and astrophysical regimes. In addition, this thesis applies the analytic approximation to laboratory-produced radiative blast waves as well as to numerical models of these experimental blast waves. These results will allow for better design of laser-based experiments with further applications to astrophysical phenomena, as well as for an increase in the understanding of the challenges involved in scaling radiative phenomena between laboratory experiments and astrophysical theory.

This investigation explores the connection between the open polar cap magnetic flux phiPCF and interplanetary conditions. phi PCF is determined from GGS/Polar VIS Earth Camera far ultraviolet observations of the aurora borealis. Observations from the GGS/Wind SWE and MFI instruments are used to characterize the interplanetary conditions. Additional observations from the IMP-8 PLA and MAG instruments are used to evaluate solar wind propagation time delay estimation methods so that the GGS/Wind observations can be better associated with the GGS/Polar observations. This allows the GGS/Wind observations to be used to estimate the polar cap potential &phis;PCP values associated with the GGS/Polar phiPCF values. Statistical methods are applied to determine a proxy relationship between &phis;PCP and phiPCF. The Rice Field Model (RFM) is modified to accept phi PCF as a configuration parameter, and RFM polar caps are produced using phi PCF determined both directly from the GGS/Polar images and by the proxy relationship from the GGS/Wind data. The RFM is able to produce polar caps with the same areas and open magnetic fluxes as the GGS/Polar observations, but the agreement in the polar cap shapes and locations leaves opportunities for further improvements.

Review and analysis of atomic collision data (such as collision cross sections and ion-neutral reaction rates) used in the upper atmospheric modeling for Earth and other planets are presented. This work gives the first complete compendium of the electron impact cross sections and ion neutral reaction rates used in aeronomic studies. This data are presented in an easy-to-use form, allowing atmospheric modelers to analyze what data were used in each existing model and permitting a choice of the best or most recent data to use in future models. An original windows-based program provides a straightforward means for viewing different upper atmosphere models altogether with the reactions and reaction rates used in each model.

Mars Global Surveyor's magnetometer/electron reflectometer (MAG/ER) experiment has returned over eight years of observations of low frequency plasma waves produced in the interaction of the solar wind with the Martian ionosphere. Using the MAG/ER data, I identify the properties and physical origins of the waves in the magnetosheath, magnetic pileup region, and ionosphere. I find that the waves in the dayside magnetosheath are predominately mirror mode instabilities produced by plasma temperature anisotropies arising from the draping of the solar wind magnetic field around the ionosphere. The nightside magnetosheath shows evidence for resonant ion instabilities arising from the interaction of the solar wind plasma with the ionospheric plasma. These waves are therefore an indirect observation of ongoing atmospheric loss at Mars. During the large solar storm of October 2003, dramatic changes were observed in the plasma waves present; even the normally placid tail region showed signs of significant wave activity. Coherent oscillations are observed in the ionosphere and are presumably driven by solar wind fluctuations or are associated with field line resonances along crustal fields.

Wave-particle interactions between hydromagnetic waves and bounce-resonant ring current ions may cause ions precipitation observed during geomagnetic storms. Uncovering mechanisms of ion loss is important to understanding the recovery phases of these storms. A computer model was developed to numerically solve Hamiltonian guiding center equations of motion for a test particle in a three-dimensional time-dependent electromagnetic field model. The background magnetic field is a simple dipole and hydromagnetic waves are modeled by time-dependent electromagnetic perturbations. Specifically, a single compressional Pc 5 wave well below the ion-cyclotron frequency was used in simulations; the amplitude of the perturbation has been varied up to the maximum observed. Bounce-resonant ring current ions near L = 3 undergo pitch angle scattering and ions are moved along the field line toward the loss cone. Wave perturbations which are superpositions of several different wave modes are also considered. Although bounce-resonant interactions alone cannot account for the observed precipitation, they may be an important part of a multi-step precipitation process.

<p> We utilize a Poisson likelihood in a maximum likelihood statistical analysis to analyze X-ray spectragraphic data. Specifically, we examine four extragalactic supernova remnants (SNR). IKT 5 (SNR 0047-73.5), IKT 25 (SNR 0104-72.3), and DEM S 128 (SNR 0103-72.4) which are designated as Type Ia in the literature due to their spectra and morphology. This is troublesome because of their asymmetry, a trait not usually associated with young Type Ia remnants. We present <i>Chandra X-ray Observatory</i> data on these three remnants, and perform a maximum likelihood analysis on their spectra. We find that the X-ray emission is dominated by interactions with the interstellar medium. In spite of this, we find a significant Fe overabundance in all three remnants. Through examination of radio, optical, and infrared data, we conclude that these three remnants are likely not "classical" Type Ia SNR, but may be examples of so-called "prompt" Type Ia SNR. We detect potential point sources that may be members of the progenitor systems of both DEM S 128 and IKT 5, which could suggest a new subclass of prompt Type Ia SNR, Fe-rich CC remnants. In addition, we examine IKT 18. This remnant is positionally coincident with the X-ray point source HD 5980. Due to an outburst in 1994, in which its brightness changed by 3 magnitudes (corrsponding to an increase in luminosity by a factor of 16) HD 5980 was classified as a luminous blue variable star. We examine this point source and the remnant IKT 18 in the X-ray, and find that its non-thermal photon index has decreased from 2002 to 2013, corresponding to a larger proportion of more energetic X-rays, which is unexpected.</p>

No description available.

<p> Over the last two decades, a large number of exoplanets have been confirmed with the rate of discovery increasing in recent years primarily as new instruments with improved sensitivities have become available. Direct imaging of an Earth-like planet is now an important goal of the science community. This is a challenging problem for two primary reasons. First, the intensity ratio between the bright star and its dim Earth-like companion is expected to be approximately ten orders of magnitude and, second, the angular separation to the star is very small. </p><p> An external occulter is a specially-shaped spacecraft that is flown in formation with a telescope in order to block most of the starlight before it reaches the entrance pupil thereby allowing planetary light outside of the occulter's inner working angle to become visible. Designing a shape for the occulter spacecraft to enable suppression over a wavelength band of interest requires modeling through scalar diffraction theory. Typical designs feature occulters that are tens of meters across at a separation of tens of thousands of kilometers from the space telescope. </p><p> In this dissertation, we focus on occulter design and scaling to enable experimental optical verification of occulters in the laboratory. We provide experimental results that establish a 10^-5 suppression level in the pupil and 10^-10 contrast in the focal plane, which are both approximately two orders of magnitude below the ideal performance of the testbed. We use numerical simulation to study the sensitivity of the occulter design in the laboratory and determine that performance is feature-size limited. We provide the design of a longer and flight-like occulter experiment, and study its sensitivity to determine the expected performance.</p>

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2008. / Title from PDF t.p. (viewed on Jul 29, 2009). Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7583. Adviser: Charles J. Horowitz.

Thesis (Ph.D.)--Indiana University, Dept. of Astronomy, 2006. / "Title from dissertation home page (viewed July 11, 2007)." Source: Dissertation Abstracts International, Volume: 67-08, Section: B, page: 4472. Adviser: Richard H. Durisen.