First global analysis of SEASAT scatterometer winds and potential for meteorological research

The first global wind fields from SEASAT-A scatterometer (SASS) data were produced. Fifteen days of record are available on tape, with unique wind directions indicated for each observation. The methodology of the production of this data set is described, as well as the testing of its validity. A number of displays of the data, on large and small scales, analyzed and gridded, are provided

A new parameterization of an empirical model for wind/ocean scatterometry

The power law form of the SEASAT A Scatterometer System (SASS) empirical backscatter-to-wind model function does not uniformly meet the instrument performance over the range 4 to 24 /ms. Analysis indicates that the horizontal polarization (H-Pol) and vertical polarization (V-Pol) components of the benchmark SASS1 model function yield self-consistent results only for a small mid-range of speeds at larger incidence angles, and for a somewhat larger range of speeds at smaller incidence angles. Comparison of SASS1 to in situ data over the Gulf of Alaska region further underscores the shortcomings of the power law form. Finally, a physically based empirical SASS model is proposed which corrects some of the deficiencies of power law models like SASS1. The new model allows the mutual determination of sea surface wind stress and wind speed in a consistent manner from SASS backscatter measurements

A Note on Frame Dragging

The measurement of spin effects in general relativity has recently taken centre stage with the successfully launched Gravity Probe B experiment coming toward an end, coupled with recently reported measurements using laser ranging. Many accounts of these experiments have been in terms of frame-dragging. We point out that this terminology has given rise to much confusion and that a better description is in terms of spin-orbit and spin-spin effects. In particular, we point out that the de Sitter precession (which has been mesured to a high accuracy) is also a frame-dragging effect and provides an accurate benchmark measurement of spin-orbit effects which GPB needs to emulate

Spectra and Symmetry in Nuclear Pairing

We apply the algebraic Bethe ansatz technique to the nuclear pairing problem with orbit dependent coupling constants and degenerate single particle energy levels. We find the exact energies and eigenstates. We show that for a given shell, there are degeneracies between the states corresponding to less and more than half full shell. We also provide a technique to solve the equations of Bethe ansatz.Comment: 15 pages of REVTEX with 2 eps figure

Search for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRAL

Measuring the polarization of the prompt gamma-ray emission from GRBs can significantly improve our understanding of both the GRB emission mechanisms, as well as the underlying engine driving the explosion. We searched for polarization in the prompt gamma-ray emission of GRB 041219a with the SPI instrument on INTEGRAL. Using multiple-detector coincidence events in the 100--350 keV energy band, our analysis yields a polarization fraction from this GRB of 99 +- 33 %. Statistically, we cannot claim a polarization detection from this source. Moreover, different event selection criteria lead to even less significant polarization fractions, e.g. lower polarization fractions are obtained when higher energies are included in the analysis. We cannot strongly rule out the possibility that the measured modulation is dominated by instrumental systematics. Therefore, SPI observations of GRB 041219a do not significantly constrain GRB models. However, this measurement demonstrates the capability of SPI to measure polarization, and the techniques developed for this analysis

Charge injection instability in perfect insulators

We show that in a macroscopic perfect insulator, charge injection at a field-enhancing defect is associated with an instability of the insulating state or with bistability of the insulating and the charged state. The effect of a nonlinear carrier mobility is emphasized. The formation of the charged state is governed by two different processes with clearly separated time scales. First, due to a fast growth of a charge-injection mode, a localized charge cloud forms near the injecting defect (or contact). Charge injection stops when the field enhancement is screened below criticality. Secondly, the charge slowly redistributes in the bulk. The linear instability mechanism and the final charged steady state are discussed for a simple model and for cylindrical and spherical geometries. The theory explains an experimentally observed increase of the critical electric field with decreasing size of the injecting contact. Numerical results are presented for dc and ac biased insulators.Comment: Revtex, 7pages, 4 ps figure

Recoiling from a kick in the head-on collision of spinning black holes

Recoil ``kicks'' induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin and then adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant relative to unequal-mass recoils even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian theory, even though the kick is generated in the nonlinear merger interaction, where post-Newtonian theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.Comment: 12 pages, 10 figures. Replaced with published version, including more discussion of convergence and properties of final hol

Development of CdZnTe pixel detectors for astrophysical applications

Over the last four years we have been developing imaging Cadmium Zinc Telluride pixel detectors optimized for astrophysical focusing hard X-ray telescopes. This application requires sensors with modest area (~2cm X 2 cm), relatively small (≾ 500µm) pixels and sub-keV energy resolution. For experiments operating in satellite orbits, low energy thresholds of ~1 - 2 keV are also desirable. In this paper we describe the desired detector performance characteristics, and report on the status of our development effort. In particular, we present results from a prototype sensor with a custom low- noise VLSI readout designed to achieve excellent spectral resolution and good imaging performance in the 2 - 100 keV band