15 documents found

Dissertation

Gamma/neutron separation in the Martian radiation environment

The Mars Science Laboratory is a NASA Mars-rover mission which was launched in November 2011, and will land on Mars in August 2012. One part of the rover is the Radiation Assessment Detector (RAD) which will measure a broad spectrum of energetic particles at the surface of Mars. The instrument consists...
Dissertation

Starbursts and active nuclei in galaxies

Starbursts and active galactic nuclei (AGN) are predominantly driven by galaxy mergers, i.e., the collision of two galaxies, but isolated galaxies, e.g., our Milky Way, can also be subject to these phenomena. Therefore this thesis is divided into two parts: in partwe investigate starbursts and AGN due...
Dissertation

Mid-infrared properties of local active galactic nuclei

The local active galactic nuclei (AGN) population enables us to study in detail the structures and radiation processes in the direct environment of the supermassive black holes in galaxy centers and to develop an understanding of the general AGN phenomenon. For this purpose, the first unbiased sample...
Dissertation

Zeitliche Entwicklung protoplanetarer Akkretionsscheiben im Strahlungsfeld...

Planeten entstehen in Akkretionsscheiben um junge Sterne. Allerdings bleibt die Frage, wie genau Mikrometer große Staubkörner zu Planeten anwachsen können, weiterhin Gegenstand der aktuellen Forschung. Ihr wird sowohl durch Beobachtungen der Scheiben und der daraus entstandenen Exoplaneten als auch durch...
Dissertation

Large-scale structure of disc galaxies

In the first part of the thesis at hand, the relation between vertical magnetic fields and dark matter in disc galaxies is studied. Under the assumption that the studied perturbations in these galaxies are stationary, we derive a mathematical relation between the mass of the dark matter and the magnetic...
Dissertation

Aktive Galaxienkerne und die Abhängigkeit ihrer Leuchtkraftfunktion von...

Im ersten Teil der Arbeit wird ein auf dem Extended-Press-Schechter-Formalismus beruhendes Monte-Carlo-Verfahren zur Erzeugung der Verschmelzungsgeschichten von Halos Dunkler Materie diskutiert. Mittels diesem wird der Einfluss unterschiedlicher kosmologischer Beschreibungen auf die Verschmelzungswahrscheinlichkeiten...
Dissertation

The Martian Radiation Environment - Early Mars and Future Measurements...

Today, the surface of Mars is an inhospitable environment for any form of life. Due to its thin atmosphere and lack of a global magnetic field, Mars is only weakly protected from charged particles impeding the planet from outer space. In particular, high-energetic galactic cosmic rays can propagate all...
Dissertation

Scintillator performance investigation for MSL/RAD

The Mars Science Laboratory (MSL) mission is a NASA Mars rover mission planned to be launched in 2011. One of the instruments onboard MSL is the Radiation Assessment Detector (RAD), a comprehensive particle measurement sensor. The instrument is divided into a RAD Sensor Head (RSH) and a RAD Electronics...
Dissertation

Multiskalensimulationen von Schwarzlochakkretion in Balkengalaxien

Balkenspiralgalaxien zeichnen sich nicht nur durch ihre namensgebenden Spiralarme und stellare Balken aus, sondern können, induziert durch das Drehmoment des Balkens, zahlreiche Strukturen in der dünnen Gasscheibe ausbilden. Zu diesen Strukturen zählen unter anderem nukleare Ringe, innere Spiralen und...
Dissertation

Solar wind and neutral atoms in the heliosphere : analysis of current data...

Here we will focus on two aspects of the heliosphere, namely the slow solar wind and energetic neutral atoms. While the slow solar wind is well characterized in its parameters, the mechanisms of its origin at the Sun are not well understood. Regarding the energetic neutral atoms neither their characteristics...
Dissertation

Measurements of Suprathermal Particles at 1 AU and in the inner Heliosphere

In this thesis, interplanetary suprathermal particles at 1 astronomical unit (AU) are studied with three time-of-flight mass spectrometers onboard three spacecraft. We study the variation and evolution of suprathermal particles during stream interaction regions (SIRs). As preparation work, the background...
Dissertation

Isotherme Modellierung kompressibler astrophysikalischer Fluide über kosmische...

Viele, oft sehr verschiedenartige, astrophysikalische Objekte weisen einen hohen Grad an Symmetrie auf. In dieser Arbeit führen Symmetrieannahmen zusammen m it der Isothermieannahme zu einem Modell, das es erlaubt, unterschiedliche physikalische Problemstellungen im Bereich der Astrophysik zu modellieren....
Dissertation

Particle Flux Directionality and other Aspects of the Martian Radiation...

Mars as a future target of manned exploration is a place of particular interest in the solar system. Both the past and the present habitability of Mars, and the safety of astronauts working on the Martian surface, depend, among other factors, on the ionizing radiation present on its surface. As part...
Dissertation

Structure and dynamics of Yukawa balls

Dissertation on the structure, in detail the shell configurations for different screenings, and dynamics, especially the structural transitions due temperature effects, of Yukawa balls, a special system of dust particles in a plasma.