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  • 1
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    Vorticity Transport and Wave Emission In A Protoplanetary Disk (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Higher order numerical algorithms (4th order in time, 3rd order in space) are applied to the Euler equations and are used to examine vorticity transport and wave motion in a non-self gravitating, initially isentropic Keplerian disk. In this talk we will examine the response of the disk to an isolated vortex with a circulation about equal to the rotation rate of Jupiter. The vortex is located on the 4 AU circle and the nebula is simulated from 1 to 24 AU. We show that the vortex emits pressure-supported density and Rossby-type wave packets before it decays within a few orbits. The acoustic density waves evolve into weak (non entropy preserving) shock waves that propagate over the entire disk. The Rossby waves remain in the vicinity of the initial vortex disturbance, but are rapidly damped. Temporal frequencies and spatial wavenumbers are derived from the nonlinear simulation data and correlated with analytical dispersion relations from the linearized Euler and energy equations.
    Keywords: Astrophysics
    Type: AGU Meeting; May 28, 2002 - May 31, 2002; Washington, DC; United States
    Format: text
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  • 2
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    A global magnetic anomaly map (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A subset of Pogo satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Through the use of a thirteenth-order field model fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus or minus 50 deg. These residuals, averaged over 1-degree latitude-longitude blocks, represent a detailed global magnetic anomaly map derived solely from satellite data. The occurrence of these anomalies on all individual satellite passes independent of local time and their decay as altitude increases imply a definite internal origin. Their wavelength structure and their correlation with known tectonic features further suggest that these anomalies are primarily of geologic origin and have their sources in the lithosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 80; Feb. 10
    Format: text
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  • 3
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    Direct measurements of natural tropospheric levels of OH via an aircraft borne tunable dye laser (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; June 197
    Format: text
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  • 4
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    Chandra Observations of Point Sources in Abell 2255 (2003)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: In our search for "hidden" AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signatures of nuclear activity, with a further two being potential AGN. Of the potential AGN, one corresponds to a galaxy with a post-starburst optical spectrum. The remaining three X-ray detected cluster galaxies consist of two starbursts and an elliptical with luminous hot gas. Of the eight cluster galaxies five are associated with luminous (massive) galaxies and the remaining three lie in much lower luminosity systems. We note that the use of X-ray to optical flux ratios for classification of X-ray sources is often misleading, and strengthen the claim that the fraction of cluster galaxies hosting an AGN based on optical data is significantly lower than the fraction based on X-ray and radio data.
    Keywords: Astrophysics
    Format: application/pdf
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  • 5
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    XMM Observations of an IXO in NGC 2276 (2003)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We present the results from a approx. 53 ksec XMM observation of NGC 2276. This galaxy has an unusual optical morphology with the disk of this spiral appearing to be truncated along the western edge. This XMM observation shows that the X-ray source at the western edge is a bright Intermediate X-ray Object (IXO). Its spectrum is well fit by a multi-color disk blackbody model used to fit optically thick standard accretion disks around black holes. The luminosity derived for this IXO is 1.1 x 10(exp 41) erg/s in the 0.5 - 10 keV band making it one of the most luminous discovered to date. The large source luminosity implies a large mass black hole if the source is radiating at the Eddington rate. On the other hand, the inner disk temperature determined here is too high for such a massive object given the standard accretion disk model. In addition to the IXO we find that the nuclear source in this galaxy has dimmed by at least a factor of several thousand in the eight years since the ROSAT HRI observations.
    Keywords: Astrophysics
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  • 6
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    Tracking the moving photocenters of active galaxies: binary black holes, accretion disks, and relativistic jets (2003)
    In:  Other Sources
    Details
    Publication Date: 2018-06-11
    Description: SIM Science Team Meeting #10 December 16-18, 2003 Pasadena, California, USA.
    Keywords: Astrophysics
    Format: text
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  • 7
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    Chandra Observations of Point Sources in A2255 (2003)
    In:  Other Sources
    Details
    Publication Date: 2018-06-06
    Description: In our search for "hidden" active galactic nuclei (AGNs), we present results from a Chandra observation of the nearby cluster A2255. Eight cluster galaxies are associated with pointlike X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with AGNs with no optical signatures of nuclear activity, with a further two being potential AGNs. Of the potential AGNs, one corresponds to a galaxy with a post-starburst optical spectrum. The remaining three X-ray-detected cluster galaxies consist of two starbursts and an elliptical with luminous hot gas. Of the eight cluster galaxies, five are associated with luminous (massive) galaxies, and the remaining three lie in much lower luminosity systems. We note that the use of X-ray-to-optical flux ratios for classification of X-ray sources is often misleading and strengthens the claim that the fraction of cluster galaxies hosting an AGN based on optical data is significantly lower than the fraction based on X-ray and radio data.
    Keywords: Astrophysics
    Type: Astrophysical Journal; Volume 597; 202-209
    Format: text
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  • 8
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    Creation and Distribution of CAIs in the Protoplanetary Nebula (2003)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: CaAl rich refractory mineral inclusions (CAIs) found at 1 - 10% mass fraction in primitive chondrites appear to be several million years older than the dominant (chondrule) components in the same parent bodies. A prevalent concern is that it is difficult to retain CAIs for this long against gas-drag-induced radial drift into the sun. We assess a hot inner (turbulent) nebula context for CAI formation, using analytical models of nebula evolution and particle diffusion. We show that outward radial diffusion in a weakly turbulent nebula can prevent significant numbers of CAI-size particles from being lost into the sun for times of 1 - 3 x 10(exp 6) years. To match the CAI abundances quantitatively, we advocate an enhancement of the inner hot nebula in silicate-forming material, due to rapid inward migration of very primitive, silicate and carbon rich, meter-sized objects. 'Combustion' of the carbon into CO would make the CAI formation environment more reduced than solar, as certain observations imply. Abundant CO might also play a role in mass-independent chemical fractionation of oxygen isotopes as seen in CAIs and associated primitive, high-temperature condensates.
    Keywords: Astrophysics
    Type: Lunar and Planetary Science XXXIV; LPI-Contrib-1156
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  • 9
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    The L = 6.6 Oosik barium plasma injection experiment and magnetic storm of March 7, 1972 (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A high-explosive shaped charge vaporizing a hollow conical liner of Ba metal and producing a fast field-aligned jet of plasma was detonated at high altitude, during a quiescent phase of a magnetic storm initiated by an ssc 10 hrs prior to the experiment, in an attempt to trace out and observe the dynamics of an auroral field line in the magnetosphere. Observations offer evidence for an upward Birkeland current sheet at the poleward edge of the auroral spiral of 8 x 10 to the minus second power A/m. Unusual features of the substorm leave open the possibility that the plasma injection may have triggered it.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 80; Mar. 1
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  • 10
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    Tectonic analysis of folds in the Colorado plateau of Arizona (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Structural mapping and analysis of folds in Phanerozoic rocks in northern Arizona, using LANDSAT-1 imagery, yielded information for a tectonic model useful in identifying regional fracture zones within the Colorado Plateau tectonic province. Since the monoclines within the province developed as a response to differential movements of basement blocks along high-angle faults, the monoclinal fold pattern records the position and trend of many elements of the regional fracture system. The Plateau is divided into a mosaic of complex, polyhedral crustal blocks whose steeply dipping faces correspond to major fracture zones. Zones of convergence and changes in the trend of the monoclinal traces reveal the corners of the blocks. Igneous (and salt) diapirs have been emplaced into many of the designated zones of crustal weakness. As loci of major fracturing, folding, and probably facies changes, the fractures exert control on the entrapment of oil and gas.
    Keywords: GEOPHYSICS
    Type: NASA-CR-145433 , OALS-BULL-9
    Format: application/pdf
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