Spatial gradients of GCR protons in the inner heliosphere derived from Ulysses COSPIN/KET and PAMELA measurements

During the transition from solar cycle 23 to 24 from 2006 to 2009, the Sun was in an unusual solar minimum with very low activity over a long period. These exceptional conditions included a very low interplanetary magnetic field (IMF) strength and a high tilt angle, which both play an important role in the modulation of galactic cosmic rays (GCR) in the heliosphere. Thus, the radial and latitudinal gradients of GCRs are very much expected to depend not only on the solar magnetic epoch, but also on the overall modulation level. We determine the non-local radial and the latitudinal gradients of protons in the rigidity range from ~0.45 to 2 GV. This was accomplished by using data from the satellite-borne experiment Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) at Earth and the Kiel Electron Telescope (KET) onboard Ulysses on its highly inclined Keplerian orbit around the Sun with the aphelion at Jupiter's orbit. In comparison to the previous A>0 solar magnetic epoch, we find that the absolute value of the latitudinal gradient is lower at higher and higher at lower rigidities. This energy dependence is therefore a crucial test for models that describe the cosmic ray transport in the inner heliosphere

The sandwich in the middle: using collective effects for stronger optomechanical coupling

Peer ReviewedPostprint (updated version

Non-equilibrium steady state of a driven levitated particle with feedback cooling

Laser trapped nanoparticles have been recently used as model systems to study fundamental relations holding far from equilibrium. Here we study, both experimentally and theoretically, a nanoscale silica sphere levitated by a laser in a low density gas. The center of mass motion of the particle is subjected, at the same time, to feedback cooling and a parametric modulation driving the system into a non-equilibrium steady state. Based on the Langevin equation of motion of the particle, we derive an analytical expression for the energy distribution of this steady state showing that the average and variance of the energy distribution can be controlled separately by appropriate choice of the friction, cooling and modulation parameters. Energy distributions determined in computer simulations and measured in a laboratory experiment agree well with the analytical predictions. We analyse the particle motion also in terms of the quadratures and find thermal squeezing depending on the degree of detuning.Comment: Submitted to the New Journal of Physic

Long distance manipulation of a levitated nanoparticle in high vacuum

Accurate delivery of small targets in high vacuum is a pivotal task in many branches of science and technology. Beyond the different strategies developed for atoms, proteins, macroscopic clusters and pellets, the manipulation of neutral particles over macroscopic distances still poses a formidable challenge. Here we report a novel approach based on a mobile optical trap operated under feedback control that enables long range 3D manipulation of a silica nanoparticle in high vacuum. We apply this technique to load a single nanoparticle into a high-finesse optical cavity through a load-lock vacuum system. We foresee our scheme to benefit the field of optomechanics with levitating nano-objects as well as ultrasensitive detection and monitoring.Comment: 12 pages 5 figure

Die Modulation der Galaktischen Kosmischen Strahlung verstehen: Beobachtungen und Theorie

The modulation of Galactic Cosmic Rays (GCRs) in the heliosphere has been a topic of ongoing research for more than 100 years. Over this time, different aspects of the modulation have been investigated, like various timescales and periodicities of variation, charge-sign effects, or dependences of the modulation strength with the particle energy. One recent example of periodic short-term variations of GCRs and Jovian electrons is analyzed in the beginning of this thesis. In 1990, the Ulysses spacecraft was launched. This mission allowed for unprecedented investigations of the spatial distribution of GCRs in the heliosphere and charge-sign effects. Two such analyses are presented in this thesis: For the A<0 solar minimum in the 2000s, the radial and latitudinal gradients of GCRs were calculated, and also charge-sign effects of this so-called unusual solar minimum were examined. However, this investigations were hindered by the fact that there were no corresponding measurements at Earth, and workarounds like comparison with same-rigidity particles of different species or assumptions regarding the behavior of different charged particles needed to be introduced. With the launch of the PAMELA detector on an Earth orbiting satellite in 2006, this gap was closed. PAMELA provided for the first time in-situ intensities of GCR electrons and protons over a wide range of energy with unprecedented energy resolution and statistics. With this tool at hand, it was possible to re-investigate the radial and latitudinal gradients of positively charged GCRs for the 2000s A<0 solar minimum with more accuracy than ever before. Additionally, the high-resolution rigidity spectrum of GCR protons provided by PAMELA allowed us to investigate the rigidity-dependence of the so-called force field approach. Demonstrating the severe limitations of this commonly used model, a straightforward and easy to use workaround introducing a rigidity-dependence is presented in the last part of this thesis.Die Modulation der Galaktischen Kosmischen Strahlung (GKS) in der Heliosphäre ist seit mehr als 100 Jahren ein Thema andauernder Forschung. Im Jahr 1990 wurde die Raumsonde Ulysses gestartet. Diese Mission erlaubte vorher nie dagewesene Untersuchungen der räumlichen Verteilung der GKS in der Heliosphäre sowie von vorzeichenabhängigen Effekten. Zwei solche Untersuchungen werden in dieser Arbeit vorgestellt: Für das A<0 solare Minimum in den 2000ern wurden die radialen und Breitengradienten der GKS berechnet. Außerdem wurden vorzeichenabhängige Effekte während dieses sogenannten ungewöhnlichen solaren Minimums untersucht. Allerdings wurden diese Analysen dadurch eingeschränkt, dass keine vergleichbaren Messungen an der Erde zur Verfügung standen. Deshalb mussten Behelfslösungen gefunden werden, etwa indem Teilchen gleicher Steifigkeit aber unterschiedlicher Spezies verglichen wurden, oder indem Annahmen betreffend des Verhaltens von Teilchen mit unterschiedlichen Ladungsvorzeichen getroffen wurden. Mit dem Start des PAMELA-Detektors auf einem die Erde umkreisenden Satelliten im Jahr 2006 wurde diese Lücke geschlossen. PAMELA ermöglichte zum ersten Mal die In-situ-Messung der GKS-Intensitäten von Elektronen und Protonen über einen großen Energiebereich mit bis dahin unerreichter Energieauflösung und Statistik. Mit diesen Mitteln konnten die radialen und Breitengradienten der GKS für das 2000er A<0 solare Minimum mit höherer Genauigkeit als je zuvor und für neue Energien untersucht werden. Darüber hinaus ermöglicht das von PAMELA gemessene, hochaufgelöste Steifigkeitsspektrum von GKS-Protonen die Untersuchung der Steifigkeitsabhängigkeit des sogenannten Force-Field-Ansatzes. Nach der Demonstration der schwerwiegenden Einschränkungen dieses weitverbreiteten Modells wird eine einfache und leicht zu nutzende Behelfslösung vorgeschlagen, die eine Steifigkeitsabhängigkeit integriert