Comparisons of Supergranule Characteristics During the Solar Minima of Cycles 22/23 and 23/24

Supergranulation is a component of solar convection that manifests itself on the photosphere as a cellular network of around 35 Mm across, with a turnover lifetime of 1-2 days. It is strongly linked to the structure of the magnetic field. The horizontal, divergent flows within supergranule cells carry local field lines to the cell boundaries, while the rotational properties of supergranule upflows may contribute to the restoration of the poloidal field as part of the dynamo mechanism that controls the solar cycle. The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended length. It is of interest to study whether the convective phenomena that influences the solar magnetic field during this time differed in character to periods of previous minima. This study investigates three characteristics (velocity components, sizes and lifetimes) of solar supergranulation. Comparisons of these characteristics are made between the minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008, respectively. It is found that whereas the lifetimes are equal during both epochs (around 18 h), the sizes are larger in 1996 (35.9 +/- 0.3 Mm) than in 2008 (35.0 +/- 0.3 Mm), while the dominant horizontal velocity flows are weaker (139 +/- 1 m/s in 1996; 141 +/- 1 m/s in 2008). Although numerical differences are seen, they are not conclusive proof of the most recent minimum being inherently unusual.Comment: 22 pages, 5 figures. Solar Physics, in pres

Generation and control of all-optical chaos in a semiconductor laser by filtered optical feedback.

In this paper, we provide a solution to the problem of producing chaotic output in a semiconductor laser, and present a theoretical description which can model the nonlinear dynamics of the laser. We draw upon the results and the knowledge that has been forthcoming from recent works on filtered optical feedback in semiconductor lasers. The most significant result, from our perspective, was that one can control the dynamical space that is available to the laser, thereby providing a mechanism for controlling its dynamical behavior. Control through the use of filters is achieved via a suitable choice of only two parameters - the detuning between the frequencies of the light emitted by the laser and the resonance of the filter, and the bandwidth of the filter - thereby providing simplicity in the experimental set u

Euratom Safeguards: Improving Safeguards by Cooperation in R&D and Implementation

Euratom Safeguards, implemented on the basis of the EURATOM Treaty by the European Commission’s Directorate Nuclear Safeguards within the Directorate General for Energy, is the largest Regional Safeguards System and involved in many R&D activities of its own, often in close cooperation with external partners. Most of the results of these activities are shared with or offered to the IAEA. This paper describes work complementary to the projects run by the European Commission Cooperative Support Programme (ECSP) to the IAEA, described elsewhere at this conference. We attempt to provide an overview on some of the R&D activities run in addition to the ECSP, and will link them to the capabilities discussed by the IAEA as part of the Long Term R&D Plan 2012. Our range of topics will include work on unattended data acquisition systems (hard- and software), advanced data analysis tools, news from seals related technology, containment and design verification applications of 3D lasers, etc. Work done with the IAEA in preparation of new facilities and facility types will be discussed briefly. The paper will also highlight some current challenges and make suggestions how to address them.JRC.E.8-Nuclear securit