15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Self-consistent modelling of pulsar magnetospheres(1989) Herold, Heinz; Ertl, Thomas; Finkbeiner, Bernd; Ruder, HannsThe magnetosphere of a rapidly rotating, strongly magnetized neutron star with aligned magnetic and rotational axes (parallel rotator) is modelled numerically. Including the radiation of the particles accelerated to relativistic energies as an efficient damping mechanism, we obtain a quasi-stationary selfconsistent solution to this classical problem. The numerical simulation, which was started from the well-known vacuum solution, yields a global magnetospheric structure that can be characterized by two regions of oppositely charged particles, which eventually produce a relativistic pulsar wind, separated by a vacuum gap of considerable extent.Item Open Access Particle motion in pulsar magnetospheres(1987) Finkbeiner, Bernd; Ertl, Thomas; Herold, Heinz; Ruder, HannsThis report discusses some new results we found in studying the trajectories of single charged particles in the vacuum magnetosphere of a pulsar using the oblique rotator model. We believe that investigations of individual particles in the vicinity of the star can be useful for a better understanding of some fundamental problems of pulsar physics, e.g. the global structure of the magnetosphere or the pulsar radiation.Item Open Access Rydberg atoms in uniform magnetic fields: uncovering the transition from regularity to irregularity in a quantum system(1986) Wunner, Günter; Woelk, Ulrich; Zech, Ingrid; Zeller, Gudrun; Ertl, Thomas; Geyer, Florian; Schweizer, Wolfgang; Ruder, HannsWe investigate the eigenvalue spectra of hydrogen Rydberg atoms in strong magnetic fields for manifestations of quantum stochasticity and find (i) a smooth transition from a Poisson-type to a Wigner-type distribution of level spacings in the range of energy where classical motion becomes increasingly chaotic, (ii) the occurrence of multiple avoided crossings, and (iii) connected with this, an extreme sensitivity of oscillator strengths, and thus of observable spectra, with respect to small variations of an external parameter, viz., the magnetic field strength.Item Open Access Generation of relativistic particles in pulsar magnetospheres(1985) Herold, Heinz; Ertl, Thomas; Ruder, HannsThe problem - fundamental for the physics of pulsars - of determining the global structure of the magnetosphere in a self-consistent way has not yet been solved satisfactorily. We report on some progress in this direction, which we have achieved by studying the trajectories of individual charged particles in the electromagnetic vacuum fields of an aligned rotator.Item Open Access Simulation mit Supercomputern : ein neues Werkzeug der Physik(1990) Ruder, Hanns; Ertl, Thomas; Geyer, Florian; Herold, Heinz; Kraus, Ute; Nollert, Hans-Peter; Rebetzky, Andreas; Schweizer, Wolfgang; Zahn, CorvinUnser Wissen über die Struktur des Kosmos und die darin enthaltenen Objekte stammt aus der sorgfältigen Analyse der auf der Erde einfallenden elektromagnetischen Strahlung,verbunden mit einer theoretischen Modellierung im Rahmen der von uns erforschten Naturgesetze. Die sprunghafte Zunahme unserer Kenntnisse in den letzten zwei Jahrzehnten verdanken wir vor allem den vielen Forschungssatelliten, die die Beobachtung kosmischer Objekte ohne die störenden Einflüsse unserer Atmosphäre erlauben. Speziell im weichen Röntgenbereich ist dadurch eine Beobachtung überhaupt erst möglich , und es ist gerade dieser Spektralbereich, der uns wesentlich neue Erkenntnisse über hochinteressante Objekte geliefert hat, da intensive Röntgenstrahlung nur unter sehr extremen physikalischen Bedingungen entsteht. Die in diesen Röntgenemissionsgebieten vorherrschenden Temperaturen, Magnet- und Gravitationsfelder sind so extrem, daß sie in irdischen Labors nicht realisiert werden können. Folglich bleibt nur die Möglichkeit, die Eigenschaften der Materie und die unter diesen Bedingungen ablaufenden physikalischen Prozesse theoretisch zu berechnen, um so - im Vergleich mit den Beobachtungen - zu zuverlässigen Aussagen über die Struktur dieser kosmischen Objekte zu gelangen.Item Open Access Effects of radiation damping on particle motion in pulsar vacuum fields(1989) Finkbeiner, Bernd; Herold, Heinz; Ertl, Thomas; Ruder, HannsThe effects of radiation reaction on the motion of charged particles are studied in strong electric and magnetic fields with special attention to the vacuum near-field region of an oblique rotator. For strong radiation damping a local velocity field is derived from the Lorentz-Dirac equation, which efficiently describes the motion of electrons and positrons in the whole range of typical pulsar parameters. The velocity field makes it possible to define regions in the inner magnetosphere, where particle trapping occurs due to the radiation losses. By numerical integration of particle trajectories from the pulsar surface, regions around the magnetic poles are found which are defined by particle emission into the wave zone. The shapes of the escape regions on the pulsar surface are determined to a considerable extent by the presence of the accumulation regions.Item Open Access Kinematics and dynamics for computer animation(1994) Ruder, Hanns; Ertl, Thomas; Gruber, Karin; Günther, Michael; Hospach, Frank; Ruder, Margret; Subke, Jörg; Widmayer, KarinThis tutorial will focus on the physical principles of kinematics and dynamics. After explaining the basic equations for point masses and rigid bodies a new approach for the dynamic simulation of multi-linked models with wobbling mass is presented, which has led to new insight in the field of biomechanics, but which has not been used in computer animation so far.Item Open Access Kinematics and dynamics for computer animation(1991) Ruder, Hanns; Ertl, Thomas; Gruber, Karin; Günther, Michael; Hospach, Frank; Subke, Jörg; Widmayer, KarinThis tutorial will focus on the physical principles of kinematics and dynamics. After explaining the basic equations for point masses and rigid bodies a new approach for the dynamic simulation of multi-linked models with wobbling mass is presented, which has led to new insight in the field of biomechanics, but which has not been used in computer animation so far.Item Open Access Towards a self-consistent modelling of pulsar magnetospheres(1987) Herold, Heinz; Ertl, Thomas; Finkbeiner, Bernd; Ruder, HannsThe numerical modelling of the general case of an oblique rotator is a very complicated time-dependent 3-dimensional problem and in its full extent probably outside the capicity of present.day computers. A considerable simplification occurs if one can assume that the essential effects may be understood by modelling the magnetosphere of an aligned rotator (where the rotation axis is parallel to the magnetic axis of the neutron star). This assumption is only reasonable for small obliqueness, since by this approach all electromagnetic wave effects are not taken into account.Item Open Access Towards a self-consistent modelling of pulsar magnetospheres(1986) Herold, Heinz; Ertl, Thomas; Ruder, HannsThe numerical modelling of the general case of an obligue rotator is a very complicated time-dependent three-dimensional problem and in its full extent probably outside the capacity of present-day computers. A considerable simplification occurs if one can assume that the essential effects may be understood by modelling the magnetosphere of an aligned rotator (where the rotation axis is parallel to the magnetic axis of the neutron star). This assumption is only reasonable for small obliguenses, since by this approach all electromagnetic wave effects are not taken into account. An advantage, however, is that unipolar induction, which should be responsible for populsting the magnetosphere with charged particles pulled out from the neutron star surface via field emission, can be studied purity.
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