Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 163 for “"Astronomy and Astrophysics"”.
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Luis Hernández: la poesía como ciencia de la vida
… Hernández was fascinated by physics, mathematics and medicine, and we also know his writing project was developed between the 60’s and the 70’s, key years for the space race. The first chapter focuses on the presence of astronomy and astrophysics in Las constelaciones (1965), the third book of …
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Trajectory design and control for formation flying spaceborne interferometers
Spaceborne interferometry promises to greatly expand our knowledge of astronomy and astrophysics, and open the doors to many new discoveries. The purpose of this study is to investigate optimal resource management techniques for separated space-craft interferometers to successfully synthesize …
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A study of postgraduate students in an Astrophysics bridging year: identifying contradictions in a complex system
Astronomy and Astrophysics have been designated one of the flagship areas of research in South Africa. As part of human capacity building in this regard, a postgraduate national teaching programme at the Honours and Masters level, the National Astrophysics and Space Science Programme (NASSP) was …
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Computationally Efficient Optimization of Formation Flying Trajectories, with Solar Radiation Pressure, near Lagrange Points
… by the National Academy of Sciences in the 2020 Astronomy and Astrophysics Decadal Survey is the investigation of exoplanets residing in habitable zones to help further the understanding of the universe by searching for extraterrestrial life. While indirect detection methods have identified a …
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The Formation Of Massive Stars: A 30 Mo Case Study
I have used a generalized Naur and Osterbrock (1953) criterion to investigate the manner in which a convective core develops. Stars more massive than {dollar}sim{dollar}30 Mo can develop convective cores before the onset of central hydrogen burning. It is estimated that stars more massive than …
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SOLAR MODULATION OF GALACTIC COSMIC RAYS: TECHNIQUES & APPLICATIONS (SHOCK ACCELERATION, ANTIPROTONS)
… in cosmic-ray intensity over the solar cycle; and the hysteresis between low and high-energy cosmic rays.</p><p>The second section contains an attempt to explain recent observations which show that cosmic-ray electrons are returning to higher intensities, characteristic of solar minimum, faster …
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ON THE SPECTRA OF GAMMA-RAY BURSTS AT HIGH ENERGIES
<p>Between 1980 February and 1983 August the Gamma-Ray Spectrometer (GRS) on the Solar Maximum Mission satellite (SMM) observed 71 gamma-ray bursts. These events form a representative subset of the class of classical gamma-ray bursts. Since their discovery more than 15 years ago, hundreds of …
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GAMMA-RAY IMAGING OBSERVATIONS OF THE CRAB AND CYGNUS REGIONS
… obtained, including observations of the Crab and Cygnus regions.</p><p>The Crab Nebula/pulsar was observed to have a featureless power-law spectrum with a best fit form of $5.1 \times 10\sp{-3} {\rm E\sb{MeV}}\sp{-1.88}$ photons ${\rm cm\sp{-2}\ s\sp{-1}\ MeV}\sp{-1},$ consistent with previous …
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HIGH ENERGY COSMIC RAY CHARGE AND ENERGY SPECTRA MEASUREMENTS ABOVE 100 GEV/NUC
<p>In 1976, 1977 and 1978, three balloon flights were conducted to measure the energy spectra of cosmic ray nuclei. A gas Cerenkov detector with different gas thresholds of 8.97, 13.12, and 17.94 GeV/nuc was employed to extend these measurements to high energies. The total collection factor for …
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An analysis of reconnection dynamics in an eruptive flare model
… Somov-Titov model, its assumptions, strengths and weaknesses. We consider the role of both the diffusion region and nonuniform resistivity in the generation of Petschek-type solutions.</p><p>The second part of this dissertation extends the averaging method to the dynamics of an asymmetric …
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Mode conversion and wave -particle interaction processes in the solar wind
… presents the theoretical study of wave coupling and wave-particle interaction processes in the solar corona and wind. We first investigate the effect of an inhomogeneous velocity field on the propagation of waves in the solar atmosphere. We find that coupling between Alfven waves and fast …
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Observation and study of giga electron volt solar energetic particles using the Milagrito extensive air shower detector
… emission from solar events can lead to an understanding of the solar energetic particle acceleration mechanism(s). Although the energy source of these mechanisms is known to reside in the solar magnetic field, the details of the acceleration process(es) have continued to elude researchers. By …
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Solar flare gamma-ray spectroscopy with CGRO-COMPTEL
<p>The X-ray and gamma-ray emission from solar flares provides important information about high-energy particles in solar flares. Energetic protons and ions interact with the solar atmosphere, giving rise to nuclear line emission at MeV energies and higher energy photons from the decay of neutral …
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Multipoint measurements of field aligned current density in the auroral zone
… dynamic auroral region with multiple bright arcs and into the polar cap. Four Free Flying Magnetometers employing autonomous, nano-spacecraft technology and designed by JPL were deployed from the main payload during the flight and multipoint magnetic field measurements were made.</p><p>Magnetic …
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Non-adiabatic features in magnetotail fast flows: Orbit tracing and data comparisons
… models of several different magnetic and electric field configurations. Fast flows in the magnetotail are selected to be modeled using a relatively thin current sheet compared with quiet times. Four different electric fields are imposed, varying in characteristic thickness and …
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Constraints on the surface composition of Trojan asteroidsfrom near infrared (0.8-4.0 μm) spectroscopy and spectral modeling
… of primitive objects provides clues to understanding the conditions under which the solar system formed. Characterization of the inner solar nebula progresses rapidly due to remote studies of asteroid and planetary surfaces as well as laboratory analyses of meteorites and lunar samples. Because …
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