A particle-in-cell (PIC) simulation study of the charging processes of spherical dust grains in a magnetized plasma environment is presented. Different magnetic field strengths with corresponding electron/ion gyration radii of smaller, the same or larger size than the grain radius and the plasma Debye length are examined. The magnetized plasma is created by overlapping the simulation box with a homogeneous, constant magnetic field. The charging currents are significantly reduced in the presence of a magnetic field, resulting in a more negative grain floating potential. Indeed, the most probable electron gyration radius is always smaller than that of ions in a Maxwellian plasma: however, it is demonstrated that the situation of simultaneous magnetized electron but an unmagnetized ion charging current never exists. The simulation results do not fit with a modified orbital motion limited (OML) theory approach for this situation, since the ion current is significantly reduced due to the increase of the gyration radius in the potential field of the dust grain. For very small gyration radii, the simulation results are in good agreement with a modified OML approach for both magnetized electron and ion charging currents.

Context: As the largest in our solar system the Jovian magnetosphere is treated in the literature as the dominant source of a few-MeV electrons, which have been measured by various spacecraft. In particular, observations obtained with Ulysses have significantly broadened the available data base. Aims: We simulated the transports of MeV electrons in the heliosphere on the basis of a time-dependent, three-dimensional modulation model. For this purpose the cosmic rays, the Jovian and the Saturnian electron sources have been, for the first time, considered together in the simulation of electron fluxes. The simulated electron intensities are discussed along the Ulysses and Cassini trajectories. The Ulysses spacecraft already passed by the planet Jupiter twice (1992, 2004), and Cassini passed by Jupiter in 2001 and reached Saturn in the year 2004. The strength of the electron source at Jupiter is relatively well known and well modelled. To determine the source strength of Saturn in comparison to that of Jupiter, we compared all available spacecraft measurements at Jupiter/Saturn in the overlapping energy range. We study the general distribution of Kronian electrons by successively using three different strengths of the Saturn source in our simulations. In addition, the effects of the solar activity are taken into account by varying the velocity field of the solar wind and the anisotropic diffusion tensor. Methods: Studying the particle diffusion is particularly relevant, because the really unknown function in the used transport equation is the diffusion tensor. The Jovian and/or Kronian electrons are suitable for studying the transport of energetic particles because the source locations are well known. Results: At 1 MeV the intensities along the Ulysses and the Cassini trajectories are clearly influenced by the presence of Kronian electrons. Conclusions: Our results reveal that the electrons from the Kronian magnetosphere, as the second largest, cannot be neglected in the very-low MeV energy range.

We report on the modelling of the time-dependent transport of a few MeV electrons in the heliosphere. These low-energetic electrons, observed with the Kiel Electron Telescope (KET) on board the Ulysses spacecraft, are for the first time simulated over a complete solar activity cycle on the basis of a time-dependent three-dimensional modulation model. It is demonstrated that the solar activity has an effect especially at high heliographic latitudes being observed by Ulysses. The findings of the Ulysses mission lasting almost 15 years now provide a substantial data base for this study. Both galactic cosmic rays and the Jovian electron source are considered for the simulation of the electron fluxes within the heliosphere. Originating from these simulations two models for the time-dependent solar wind expansion are suggested, formulated and tested.Both characterise the varying velocity field of the solar wind over a solar cycle. A time-dependent anisotropic diffusion tensor was also tested in order to figure out from KET observations the variation of the release rate of low-energetic electrons from the Jovian magnetosphere.

The OPAR-Code is a tool for Plasma Simulations with fixed spherical dust particles in it. The surface of the dust particle(s) is set as a inner boundary condition according to the surface potential, calculated from the dust charge. This inner boundary condition is time-dependent and can be different in the next timestep, because the charge of the dust particle(s) can change according to the collection of plasma particles.

Plasma embedded dust grains getting charged because plasma particles hitting the grain surface and will be absorbed. Due to the larger mobility of electrons grains acquire a negativ floating charge. A dynamical equilibrium charge is reached when electron and ion current to the grain are equal. The charging currents are substantially changed if an external magnetic field is present because plasma particles motion becomes aligned with the field lines. In this work a particle-in-cell (PIC) simulation study of the charging of single, stationary and spherical grains in magnetized plasma environment is presented.

The Jovian magnetosphere as the largest in our solar system is treated in the literature as the dominant source of a few-MeV electrons, which have been measured by various spacecraft. On the basis of a time-dependent threedimensional modulation model the transport of MeV electrons in the heliosphere is simulated. For this purpose the cosmic rays, the Jovian and the Saturnian electron sources are, for the first time, considered together in the simulation of electron fluxes. The simulated electron intensities are discussed along the Ulysses and Cassini trajectories (see Fig. 1). Our results reveal that the electrons from the Kronian magnetosphere, as the second largest, can not be neglected in the very-low MeV energy range.

The invention relates to an overvoltage protection comprising a spark gap and a laser to ignite the spark gap. The laser is connected to an input of an optical elongation element which serves to temporally elongate the laser pulses generated by the laser.

The invention relates to a method for manufacturing an arrester assembly which comprises at least two overvoltage arresters with resistance elements which operate as a function of the voltage and are connected electrically in series.

The invention relates to an arrangement and a method for the galvanically separated energy transmission, in which the energy is transmitted via a dielectric waveguide.

Die Erfindung betrifft eine Anordnung sowie ein Verfahren zur galvanisch getrennten Energieübertragung, bei denen die Übertragung durch einen dielektrischen Wellenleiter erfolgt, mit dem mindestens zwei Gleichrichtereinrichtungen eine funktionale Verbindung aufweisen, die derart ausgestaltet ist, dass den jeweiligen Gleichrichtereinrichtungen eine die Energieübertragung kennzeichnenden Leistung derart aufgeteilt zugeführt wird, dass jede Gleichrichtereinrichtung eingangsseitig den gleichen Leistungswert erhält.

The invention relates to a surge protector comprising a spark gap and a laser for ignition of the spark gap. The surge protector is characterized in that a laser-active medium of the laser is arranged on the spark gap to generate laser radiation. The pump source of the laser is arranged in spaced relation to the laser-active medium.

In order to provide a spark gap for overvoltage protection, said spark gap having electrodes that face each other and having a short deionization time, the electrodes have, on at least a portion thereof, current-path bounding means for forcing a desired current path in the electrodes themselves.

Ein staubiges oder komplexes Plasma besteht neben den Elektronen, Ionen und Neutralgasteilchen aus kompakten Partikeln im Mikro- oder Submikrometerbereich. Die Staubpartikel wechselwirken mit den Plasmateilchen und laden sich elektrisch auf, bis eine Gleichgewichtsladung erreicht ist, welche von der Größe der Staubteilchen und den Plasmaparametern abhängt. Die Gleichgewichtsladung oder das Gleichgewichtspotenzial stellt eine der charakteristischen Größen eines staubigen Plasmas dar. Eine analytische Bestimmung des Gleichgewichtspotenzials für sphärische Staubteilchen ist mit der OML-Theorie möglich, welche allerdings lediglich in einem eingeschränkten Parameterbereich eine gute Approximation darstellt, nämlich wenn das Staubteilchen kleiner als die Debyelängen des Plasmasystems ist und kein Magnetoplasma vorliegt. Die wesentlich aufwändigere OM-Theorie erlaubt die Bestimmung des Gleichgewichtspotenzials in Abhängigkeit des Staubteilchenradius, wobei eine numerische Lösung der Poissongleichung erforderlich ist. In dieser Arbeit wird mit dem "`Particle-In-Cell"'-Code OPAR die Aufladung von einzelnen, sphärischen Staubteilchen unterschiedlicher Größe bis zum Erreichen des Gleichgewichtszustands untersucht. Die Staubteilchen sind dabei als innere und ortsfeste Randbedingungen mit einer zeitabhängigen Staubteilchenladung implementiert. In den OPAR-Simulationen werden Elektronen und Ionen dynamisch betrachtet, wobei das Simulationsgebiet durch entsprechende äußere Randbedingungen in ein "unendlich" ausgedehntes, ungestörtes Maxwellplasma eingebettet ist. Es sind Plasmasysteme bei verschiedenen Temperaturverhältnissen (Ionen zu Elektronen) sowie mit verschiedenen Staubteilchenradien simuliert worden. Die Radien fallen dabei kleiner als auch größer als die Debyelängen des betrachteten Plasmasystems aus. Es werden die Gleichgewichtspotenziale, die Elektronen- und Ionendichten in der Umgebung des Staubteilchens sowie der Potenzialverlauf sowohl für Plasmasysteme ohne Magnetfeld als auch für Magnetoplasmen mit unterschiedlichen magnetischen Flussdichten diskutiert. Das Magnetoplasma wird dabei durch die Überlagerung des Simulationsgebietes mit einem homogenen und konstanten Magnetfeld erzeugt. Die Ladungsströme auf ein sphärisches Staubteilchen verlieren in einem Magnetoplasma die Rotationssymmetrie, welche in der OML- und OM-Theorie angesetzt wird. Da Elektronen stärker an Magnetfeldlinien gebunden werden als Ionen, wird der Elektronenstrom auf ein Staubteilchen stets stärker beeinflusst als der Ionenstrom. Mit Hilfe der OML-Theorie werden qualitative Aussagen über das Verhalten des Gleichgewichtspotenzials unter dem Einfluss eines Magnetfeldes analytisch abgeleitet und mit den Simulationsergebnissen verglichen, wobei insbesondere der Übergang zwischen dem unmagnetisierten und dem voll magnetisierten Fall untersucht und modelliert wird.

The modulation of the time-dependent transport of energetic particles in the heliosphere is considered in this diploma thesis. Energetic electrons, observed with the Kiel Electron Telescope (KET) on board the Ulysses spacecraft, are simulated over a complete solar activity cycle on the basis of a three-dimensional model for the first time. It is demonstrated that the solar activity has an effect especially at high heliographic latitudes. For the first time the solar wind and energetic electrons were observed in these high latitudes by Ulysses. The findings of the Ulysses mission lasting now almost 14 years provide a substantial base for this study. The Jovian electron source is considered for the simulation of the electron fluxes within the heliosphere as well. In line with these simulations two models are suggested, formulated and tested. Both characterize the varying velocity fields of the solar wind over a solar cycle. A time-dependent anisotropic diffusion tensor was also tested, in order to figure out the variation of the emission rate of Jovian electrons from KET observations.