NASA activities and interests in the 1979 regional and storm scale experiment

A brief overview is presented of NASA's planned involvement in an interagency severe storms field measurement program

A general form of the co-moving tensorial derivative

A general expression for the co-moving derivative of a tensor is derived. A variable describing the coordinate velocity field is introduced. Time dependency of the metric elements is expressed in terms of this velocity field. The resulting description of motion is one of which the Eulerian and Lagrangian viewpoints are special cases. This general description is useful in problems involving moving boundaries or discontinuities

Pressure Contact Sounding Data for NASA's Atmospheric Variability Experiment (AVE 3)

The basic rawinsonde data are described at each pressure contact from the surface to sounding termination for the 41 stations participating in the AVE III measurement program that began at 0000 GMT on February 6 and ended at 1200 GMT on February 7, 1975. Soundings were taken at 3-hour intervals during a large period of the experiment from most stations within the United States east of about 105 degrees west longitude. Methods of data processing, change in reduction scheme since the AVE II pilot experiment, and data accuracy are briefly discussed. An example of contact data is presented, and microfiche cards of all the contact data are included in the appendix. The AVE III project was conducted to better understand and establish the extent of applications for meteorological satellite sensor data through correlative ground truth experiments and to provide basic experimental data for use in studies of atmospheric scales of-motion interrelationships

Diffraction-contrast imaging of cold atoms

We consider the inverse problem of in-line holography, applied to minimally-destructive imaging of cold atom clouds. Absorption imaging near-resonance provides a simple, but destructive measurement of atom column density. Imaging off resonance greatly reduces heating, and sequential images may be taken. Under the conditions required for off-resonant imaging, the generally-intractable inverse problem may be linearized. A minimally-destructive, quantitative and high-resolution image of the atom cloud column density is then retrieved from a single diffraction pattern.Comment: 4 pages, 3 figures v2: minor changes in response to referee reports, mostly additional experimental detail v3: revisions to figure 3: added trace and changed image. Minor text and referencing changes. Accepted by Phys Rev A (Rapid Commun

Plasma Relaxation and Topological Aspects in Hall Magnetohydrodynamics

Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient alpha in the Hall MHD Beltrami condition turns out now to be proportional to the "potential vorticity." The Hall MHD Beltrami condition becomes equivalent to the "potential vorticity" conservation equation in two-dimensional (2D) hydrodynamics if the Hall MHD Lagrange multiplier beta is taken to be proportional to the "potential vorticity" as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as "potential vorticity" lines in 2D hydrodynamics

SHEEP: The Search for the High Energy Extragalactic Population

We present the SHEEP survey for serendipitously-detected hard X-ray sources in ASCA GIS images. In a survey area of $\sim 40$ deg$^{2}$, 69 sources were detected in the 5-10 keV band to a limiting flux of $\sim 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. The number counts agree with those obtained by the similar BeppoSAX HELLAS survey, and both are in close agreement with ASCA and BeppoSAX 2-10 keV surveys. Spectral analysis of the SHEEP sample reveals that the 2-10 and 5-10 keV surveys do not sample the same populations, however, as we find considerably harder spectra, with an average $\Gamma\sim1.0$ assuming no absorption. The implication is that the agreement in the number counts is coincidental, with the 5-10 keV surveys gaining approximately as many hard sources as they lose soft ones, when compared to the 2-10 keV surveys. This is hard to reconcile with standard AGN ``population synthesis'' models for the X-ray background, which posit the existence of a large population of absorbed sources. We find no evidence of the population hardening at faint fluxes, with the exception that the few very brightest objects are anomalously soft. 53 of the SHEEP sources have been covered by ROSAT in the pointed phase. Of these 32 were detected. An additional 3 were detected in the RASS. As expected the sources detected with ROSAT are systematically softer than those detected with ASCA alone, and of the sample as a whole (truncated).Comment: 36 pages, 7 figs, to appear in Ap

Comprehensive Organic Analysis of Antartic Micrometeorites

Introduction: Micrometeorites (MMs) are thought to be significant contributors of organic material to the early Earth [1], and a variety of techniques have been employed to identify their organic composition [2-6]. These include the identification of key organic groups using combinations of infrared, energy dispersive Xray, electron energy loss and Raman spectroscopy and scanning transmission X-ray microscopy [2-4], highlighting similarities between that of MMs and carbonaceous chondrites. Few studies, however, have focused on the characterisation of individual micrometeoritic organic components. Microscopic L2MS has been used to identify up to C5 polycyclic aromatic hydrocarbons and their alkyl derivatives [5]. A combination of ionexchange chromatography and fluorimetric detection has also been successful in identifying a number of protein amino acids including glycine and alanine [6]. We have previously reported a method to analyse ?g-sized quantities of extraterrestrial materials, with prior application to assessing organic volatile release from MM atmospheric entry heating simulations [7]. In this study we utilise this technique to characterise the organic composition of Antarctic terrestrial particles and MMs collected in 1994 from Cap-Prudhomme [8]