• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 13
  • 1
  • Tagged with
  • 13
  • 13
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A multi-frequency study of the Sunyaev Zel'dovich effect and its polarization in cosmic structures

Emritte, Mohammad Shehzad 21 July 2014 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 24 May 2014. / The Sunyaev-Zel'dovich e ect (hereafter SZE), i.e. the distortion of the cosmic microwave background (CMB) spectrum due to inverse Compton scattering of CMB photons o energetic electrons in cosmic structures, is a relevant inves- tigation tool for astrophysical and cosmological studies. Since the SZE is an interaction between photons and electrons, polarization arises as a natural out- come and then provides the SZE with an important complementary component as an astrophysical and cosmological probe. This thesis is an extensive study on the SZE in non-relativistic and relativistic regime including polarization. We rst perform a study on a set of galaxy clusters hosting radio halos where we constrain the non-thermal pressure present in these structures using multifre- quency data such as SZE, radio and X-ray. We found that the average ratio between non-thermal to thermal pressure is 0:5. We then derive, in the full relativistic regime, a general formulation of the properties of the SZE, and we further derive the Stokes parameters, Q and U, of the polarized SZE. This is done in a general case by solving the polarized Boltzmann collisional integral in the Thomson limit that allows us to extract the Stokes parameters for arbitrary electron distribution functions. We further discuss the spectral features of the SZE polarization as produced by other additional e ects occurring in the clus- ter atmospheres, like nite optical depth e ects and transverse plasma motions. We nally apply the results of our study to di erent cosmic structures (e.g. galaxy clusters and radio galaxies) and we discuss the relevance of SZE polar- ization in the study of extragalactic astrophysical plasmas and for cosmological applications.
2

Waves in space plasmas : lower hybrid cavities and simple-pole distribution functions /

Tjulin, Anders, January 2003 (has links)
Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 6 uppsatser.
3

Elites and paradigms; a sociological analysis of the Big Bang and plasma debate in theoretical cosmology.

Ipe, Alex I. (Alex Ike), January 1900 (has links)
Thesis (M.A.)--Carleton University, 1996. / Also available in electronic format on the Internet.
4

Laboratory investigations of Alfvén waves in a high power helicon plasma with density gradients

Houshmandyar, Saeid. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains xxii, 186 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
5

Spectroscopy of H [superscript] + [subscript] 3 in laboratory and astrophysical plasmas /

McCall, Benjamin John. January 2001 (has links)
Thesis (Ph. D.)--University of Chicago, Department of Chemistry and Department of Astronomy and Astrophysics, June 2001. / Includes bibliographical references. Also available on the Internet.
6

Atomic data generation and collisional radiative modeling of Ar II, Ar III, and Ne I for laboratory and astrophysical plasmas

Muñoz Burgos, Jorge Manual, Boivin, Robert François, Loch, Stuart David, January 2009 (has links)
Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 184-188).
7

Study of warm dense matter and high energy density physics. / 溫暖稠密物質及高能量密度物理的研究 / Study of warm dense matter and high energy density physics. / Wen nuan chou mi wu zhi ji gao neng liang mi du wu li de yan jiu

January 2009 (has links)
Ng, Siu Fai = 溫暖稠密物質及高能量密度物理的研究 / 吳肇輝. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 126-133). / Abstracts also in Chinese. / Ng, Siu Fai = Wen nuan chou mi wu zhi ji gao neng liang mi du wu li de yan jiu / Wu Zhaohui. / Chapter 1 --- Introduction --- p.16 / Chapter 1.1 --- General review of high energy density physics --- p.16 / Chapter 1.2 --- General review of warm dense matter --- p.20 / Chapter 1.2.1 --- Physics of warm dense matter --- p.20 / Chapter 1.2.2 --- Uncertainties of warm dense matter --- p.23 / Chapter 1.2.3 --- Challenges of warm dense matter studies --- p.25 / Chapter 1.3 --- Use of intense heavy ion beam --- p.27 / Chapter 1.4 --- Motivation and structure of this thesis --- p.32 / Chapter 2 --- Hydrodynamic simulations --- p.34 / Chapter 2.1 --- Lagrangian hydrodynamic code --- p.34 / Chapter 2.2 --- Hydrodynamic equations --- p.35 / Chapter 2.3 --- Artificial viscosity --- p.36 / Chapter 3 --- Equations of state --- p.38 / Chapter 3.1 --- Van der Waals' equation of state --- p.39 / Chapter 3.2 --- Quotidian equation of state --- p.41 / Chapter 3.3 --- Saha-based equation of state --- p.41 / Chapter 3.4 --- Inverse power potentials equation of state --- p.48 / Chapter 3.5 --- Gruneisen-type equation of state --- p.53 / Chapter 3.6 --- Discussion --- p.59 / Chapter 4 --- Single bubble sonoluminescence --- p.63 / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Theory of sonoluminescence --- p.65 / Chapter 4.2.1 --- Bubble wall dynamics --- p.66 / Chapter 4.2.2 --- Radiation transport --- p.67 / Chapter 4.2.3 --- Diffusive stability --- p.68 / Chapter 4.3 --- Numerical simulation --- p.68 / Chapter 4.3.1 --- Determination of the ambient radius --- p.69 / Chapter 4.3.2 --- Simulations using SEOS --- p.70 / Chapter 4.3.3 --- Simulations using QEOS --- p.77 / Chapter 4.4 --- Conclusion --- p.82 / Chapter 5 --- Collapsing bubble in ion-beam-heated metal --- p.83 / Chapter 5.1 --- Introduction --- p.83 / Chapter 5.2 --- Bubble collapse --- p.86 / Chapter 5.2.1 --- First step of collapse --- p.88 / Chapter 5.2.2 --- Stagnation point and bubble size --- p.89 / Chapter 5.2.3 --- Outer boundary and metal thickness --- p.91 / Chapter 5.2.4 --- Metal layer just outside bubble --- p.93 / Chapter 5.3 --- Effect of equation of state used --- p.95 / Chapter 5.3.1 --- Inverse power potentials equation of state --- p.95 / Chapter 5.3.2 --- Effect of ionization --- p.97 / Chapter 5.3.3 --- Effect of hard core --- p.97 / Chapter 5.3.4 --- Effect of EOS for metal --- p.97 / Chapter 5.4 --- Effect of proposed experimental parameters --- p.102 / Chapter 5.4.1 --- Initial gas density --- p.102 / Chapter 5.4.2 --- Energy deposition rate --- p.102 / Chapter 5.5 --- Conclusion and discussion --- p.105 / Chapter 6 --- High coupling efficiency compression by intense ion beams --- p.108 / Chapter 6.1 --- Introduction --- p.108 / Chapter 6.2 --- Ion stopping formulation --- p.111 / Chapter 6.3 --- Numerical simulation --- p.112 / Chapter 6.3.1 --- Lithium hydride target --- p.112 / Chapter 6.3.2 --- Underdense aluminum foam --- p.118 / Chapter 6.4 --- Conclusion --- p.119 / Chapter 7 --- Conclusion --- p.121 / Chapter 7.1 --- Summary --- p.121 / Chapter 7.2 --- Suggestions for future work --- p.123 / Bibliography --- p.126
8

Exploring the Alfvén-wave acceleration of auroral electrons in the laboratory

Schroeder, James William Ryan 01 August 2017 (has links)
Inertial Alfvén waves occur in plasmas where the Alfvén speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfvén waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfvén waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfvén waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfvén waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfvén waves, the measured portion of the distribution function oscillates at the Alfvén wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfvén wave antennas. The oscillation of the distribution function is described by a purely Alfvénic model when the Alfvén wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvénic and non-Alfvénic effects. Indications of a nonlinear interaction between electrons and inertial Alfvén waves are present in recent data.
9

Global instabilities in rotating magnetized plasmas

Pino, Jesse Ethan, 1981- 16 October 2012 (has links)
The Magnetorotational Instability (MRI) is believed to be the primary mechanism for angular momentum transfer in astrophysical accretion disks. This instability, which exists in ionized disks in the presence of weak magnetic fields, can either transfer angular momentum directly, or give rise to anomalous viscosity via non-linear turbulence. While many previous analytical treatments are concerned with the local theory of the MRI, when the length scale of rotation shear is comparable to the length scale of the most unstable modes, a global analysis is necessary. In this dissertation we investigate the global theory of the linear MRI. In particular, we show how rotation shear can localize global modes and how the global growth rates can differ signicantly from the local approximation in certain cases. Changes in the equilibrium density are considered. In addition, the effects of Hall Magnetohydrodynamics on the MRI are studied in both the local and global cases. / text
10

Global instabilities in rotating magnetized plasmas

Pino, Jesse Ethan, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2009. / Title from PDF title page (University of Texas Digital Repository, viewed on Sept. 9, 2009). Vita. Includes bibliographical references.

Page generated in 0.0734 seconds