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Articles 1231 - 1260 of 1383

Full-Text Articles in Physical Sciences and Mathematics

Thirty-Five New Pulsating Da White Dwarf Stars, Anjum S. Mukadam, Ted Von Hippel, Et Al. Jun 2004

Thirty-Five New Pulsating Da White Dwarf Stars, Anjum S. Mukadam, Ted Von Hippel, Et Al.

Publications

We present 35 new pulsating DA (hydrogen atmosphere) white dwarf stars discovered from the Sloan Digital Sky Survey (SDSS) and the Hamburg Quasar Survey (HQS). We have acquired high-speed time series photometry of preselected DA white dwarfs with a prime focus CCD photometer on the 2.1 m telescope at McDonald Observatory over 15 months. We selected these stars on the basis of prior photometric and spectroscopic observations by the SDSS and HQS. For the homogeneous SDSS sample, we achieve a success rate of 80% for finding new variables at a detection threshold of 0.1%-0.3%. With 35 newly discovered DA variable …

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Re-Defining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, D. E. Winget,, M. H. Montgomery May 2004

Re-Defining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, D. E. Winget,, M. H. Montgomery

Publications

We use the new ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to re-define the empirical ZZ Ceti instability strip. This is the first time since the discovery of white dwarf variables in 1968 that we have a homogeneous set of spectra acquired using the same instrument on the same telescope, and with con- sistent data reductions, for a statistically significant sample of ZZ Ceti stars. The homogeneity of the spectra reduces the scatter in the spectroscopic temperatures and we find a narrow instability strip of width ∼ …

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Data-Model Comparison Search Analysis Of Coincident Pbo Balmer Α, Eurd Lyman Β Geocoronal Measurements From March 2000, J. Bishop, E. J. Mierkiewicz, F. L. Roesler, J. F. Gómez, C. Morales May 2004

Data-Model Comparison Search Analysis Of Coincident Pbo Balmer Α, Eurd Lyman Β Geocoronal Measurements From March 2000, J. Bishop, E. J. Mierkiewicz, F. L. Roesler, J. F. Gómez, C. Morales

Publications

Recent Lyman series and Balmer series airglow measurements provide a fresh opportunity to investigate the density distribution and variability of atomic hydrogen in the upper atmosphere. Dedicated nightside Balmer α Fabry-Perot spectrometer measurements at the Pine Bluff Observatory (PBO), University of Wisconsin-Madison, have been acquired since late 1999 taking advantage of several technological advances. Extreme ultraviolet spectral radiance measurements by the Espectrógrafo Ultravioleta extremo para la Radiación Difusa (EURD) instrument on the Spanish MINISAT-1 satellite from October 1997 to December 2001 provide extensive sets of geocoronal Lyman β, Lyman γ and He 584 Å emission intensities. In this paper, coincident …

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Interstellar H3+ Line Absorption Toward Lkhα 101, Sean D. Brittain, Theodore Simon, Craig Kulesa, Terrence W. Rettig May 2004

Interstellar H3+ Line Absorption Toward Lkhα 101, Sean D. Brittain, Theodore Simon, Craig Kulesa, Terrence W. Rettig

Publications

We present a detection of three lines of the H+3 ion in the near-infrared spectrum of the Herbig Be star LkHalpha 101. H+3 is the principal initiator of gas-phase chemistry in interstellar clouds and can be used to constrain the ionization rate or the path length through interstellar material along the line of sight. Essentially all of the observed H+3 column of (2.2+/-0.3)×1014 cm-2 toward LkHalpha 101 originates in the same dense, dark cloud; less than 1 mag of the ~11 total magnitudes of visual extinction is attributable to diffuse material. Constraints on the density [1×104cm-3

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Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, D. K. Sing, Terry D. Oswalt, J. B. Holberg, M. R. Burleigh, S. A. Good, Et Al. May 2004

Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, D. K. Sing, Terry D. Oswalt, J. B. Holberg, M. R. Burleigh, S. A. Good, Et Al.

Publications

Extensive photometric and spectroscopic observations have been obtained for HS 1136+6646. The observations reveal a newly formed post–common-envelope binary system containing a hot ~DAO.5 primary and a highly irradiated secondary. HS 1136+6646 is the most extreme example yet of a class of short-period hot H-rich white dwarfs with K–M companion systems such as V471 Tau and Feige 24. HS 1136+6646 is a double-line spectroscopic binary showing emission lines of H i, He ii, C ii, Ca ii, and Mg ii, due in part to irradiation of the K7 V secondary by the hot white dwarf. Echelle spectra reveal the hydrogen …

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Beryllium Abundances In F And G Dwarfs In Praesepe And Other Young Clusters From Keck Hires Observations, Ann Merchant Boesgaard, Eric Armengaud, Jeremy R. King Apr 2004

Beryllium Abundances In F And G Dwarfs In Praesepe And Other Young Clusters From Keck Hires Observations, Ann Merchant Boesgaard, Eric Armengaud, Jeremy R. King

Publications

The study of both Be and Li gives useful clues about stellar internal structure. Of particular interest is the study of these light elements in open clusters, which have a known age and metallicity. In this paper we present a study of Be abundances in 10 F-type stars in Praesepe and a comprehensive discussion about Be abundances in other open clusters: Hyades, Pleiades, Per, Coma, and UMa. We have made observations of the doublet of Be ii around 3130 A˚ in Praesepe stars, using the Keck I telescope and the High Resolution Echelle Spectrometer (HIRES). Beryllium abundances were derived from …

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Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras Apr 2004

Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras

Publications

Data from the four spacecraft Cluster mission during a high altitude cusp crossing on 13 February 2001 are presented. The spacecraft configuration has one leading spacecraft, with the three trailing spacecraft lying in a plane that corresponds roughly to the nominal magnetopause surface. The typical spacecraft separation is approximately 600 km. The encounter occurs under conditions of strong and steady southward Interplanetary Magnetic Field (IMF). The cusp is identified as a seven-minute long depression in the magnetic field, associated with ion heating and a high abundance of He+. Cusp entry involves passage through a magnetopause boundary that has undergone very …

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Oxygen In Open Cluster Dwarfs: Pleiades And M34, Simon C. Schuler, Jeremy R. King, L M. Hobbs, Marc H. Pinsonneault Feb 2004

Oxygen In Open Cluster Dwarfs: Pleiades And M34, Simon C. Schuler, Jeremy R. King, L M. Hobbs, Marc H. Pinsonneault

Publications

We analyze the high-excitation O I lambda7774 triplet in high-resolution, moderate signal-to-noise ratio spectra of 15 Pleiades and eight M34 open cluster dwarfs over the effective temperature range of 5048-6172 K. Relative O abundances have been derived using model atmospheres interpolated from four different sets of ATLAS9 grids. In contrast to existing non-LTE (NLTE) predictions, a dramatic increase in the O I triplet abundance with decreasing temperature is seen for both clusters, regardless of the atmospheric model. S I abundances of three Pleiades stars derived from the high-excitation lambda6053 feature mimic the O I abundance behavior. O abundances have also …

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Laser Induced Desorption Time Of Flight Mass Spectrometer Analysis Of Adsorbed Contaminants On Vacuum Ultraviolet Lithography Optic Materials, Susan D. Allen, Yamini Surpaneni Feb 2004

Laser Induced Desorption Time Of Flight Mass Spectrometer Analysis Of Adsorbed Contaminants On Vacuum Ultraviolet Lithography Optic Materials, Susan D. Allen, Yamini Surpaneni

Publications

Adsorbed surface contaminants on optical elements absorb light energy in an optical lithography system and, if left unclean, will result in reduced wafer yield. In order to nondestructively analyze the surface adsorbate of different CaF2 samples, a laser induced desorption-Time of Flight Mass Spectrometer (LID-TOFMS) technique was developed. The main object of this technique is to investigate the surface composition of adsorbed contaminants as a function of position on the sample. An Er:YAG laser at 2.94 μm was used as the light source to induce desorption. Electron impact ionization was used to obtain ionization of desorbed molecules. The detection of …

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Book Review: The Big Bang: A View From The 21st Century, T. D. Oswalt Feb 2004

Book Review: The Big Bang: A View From The 21st Century, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Big Bang : a View from the 21st Century by David M. Harland. Springer/Praxis, 2003 262p, 1-85233-713-3 $39.95.

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Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto Feb 2004

Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto

Publications

The Kelvin-Helmholtz instability (KHI) in its nonlinear stage can develop small-scale filamentary field and current structures at the flank boundaries of the magnetosphere. It has been shown previously with MHD simulations that magnetic reconnection can occur inside these narrow current layers, resulting in plasma transport from the solar wind into the magnetosphere. During periods of northward IMF, this transport is sufficient to generate a cold, dense plasma sheet on time scales consistent with satellite observations. However, when the length scales of these narrow current layers approach the ion inertia scale, the MHD approximation is not valid anymore and the Hall …

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Existence Of Solutions To A Hamiltonian System Without Convexity Condition On The Nonlinearity, Gregory S. Spradlin Feb 2004

Existence Of Solutions To A Hamiltonian System Without Convexity Condition On The Nonlinearity, Gregory S. Spradlin

Publications

We study a Hamiltonian system that has a superquadratic potential and is asymptotic to an autonomous system. In particular, we show the existence of a nontrivial solution homoclinic to zero. Many results of this type rely on a convexity condition on the nonlinearity, which makes the problem resemble in some sense the special case of homogeneous (power) nonlinearity. This paper replaces that condition with a different condition, which is automatically satisfied when the autonomous system is radially symmetric. Our proof employs variational and mountain-pass arguments. In some similar results requiring the convexity condition, solutions inhabit a submanifold homeomorphic to the …

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Technology And Mathematics Standards: An Integrated Approach, Chris Merrill, Mark Comerford Jan 2004

Technology And Mathematics Standards: An Integrated Approach, Chris Merrill, Mark Comerford

Publications

The article focuses on the use of standards-based teaching and learning that has been gaining significant attention in the education world. State and national associations now base their specific subject area or discipline solely on standards, i.e., International Technology Education Association (ITEA), National Council of Teachers of Mathematics (NCTM), National Science Education Association (NSEA). Moreover, at the public school level, state boards of education are holding school districts accountable for teaching standards-based curricula. It is with the latter definition in mind that the authors created a standards-based, integrated technology and mathematics lesson using the design and construction of stair systems.

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The Host Of Grb 030323 At Z=3.372: A Very High Column Density Dla System With A Low Metallicity, P. M. Vreeswijk, S. L. Ellison, C. Ledoux, R. A. M. J. Wijers, J. P. U. Fymbo, P. Møller, A. Henden, J. Hjorth, G. Masi Jan 2004

The Host Of Grb 030323 At Z=3.372: A Very High Column Density Dla System With A Low Metallicity, P. M. Vreeswijk, S. L. Ellison, C. Ledoux, R. A. M. J. Wijers, J. P. U. Fymbo, P. Møller, A. Henden, J. Hjorth, G. Masi

Publications

We present photometry and spectroscopy of the afterglow of GRB 030323. VLT spectra of the afterglow show damped Lyα(DLA) absorption and low- and high-ionization lines at a redshift z =3.3718 ±0.0005. The inferred neutral hy-drogen column density, log N(H i) =21.90±0.07, is larger than any (GRB- or QSO-) DLA H  column density inferred directly from Lyαin absorption. From the afterglow photometry, we derive a conservative upper limit to the host-galaxy extinction: AV <0.5 mag. The iron abundance is [Fe/H] =−1.47 ±0.11, while the metallicity of the gas as measured from sulphur is [S/H] =−1.26 ±0.20. We derive an upper limit on the H2 molecular fraction of 2N(H2)/(2N(H2) +N(H i)) <∼10−6.In the Lyαtrough, a Lyαemission line is detected, which corresponds to a star-formation rate (not corrected for dust extinction) of roughly 1 Myr−1. All these results are consistent with the host galaxy of GRB 030323 consisting of a low metallicity gas with a low dust content. We detect fine-structure lines of silicon, Si*, which have never been clearly detected in QSO-DLAs; this suggests that these lines are produced in the vicinity of the GRB explosion site. Under the assumption that these fine-structure levels are populated by particle collisions, we estimate the H  volume density to be nH i =102−104 cm−3.HST/ACS imaging 4 months after the burst shows an extended AB(F606W) =28.0 ±0.3 mag object at a distance of 0.14 (1 kpc) from the early afterglow location, which presumably is the host galaxy of GRB 030323.

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Response Of Dark-Adapted Retinal Rod Photoreceptors, H. Khanal, V. Alexiades, E. Dibenedetto Jan 2004

Response Of Dark-Adapted Retinal Rod Photoreceptors, H. Khanal, V. Alexiades, E. Dibenedetto

Publications

The process of phototransduction, whereby light is converted into an electrical response, in rod and cone photoreceptors in the retina, involves as a key setp, the diffusion of the cytoplasmic, signaling molecules cGMP (cyclic guanosime monophosphate) and Ca2+ diffuse in the cytoplasm (the fluid surrounding the discs). the complex geometry of the rod creates computational difficulties. We present spatio-temporal compuational models for interacctions and diffusion of cGMP and Ca2+ in the cytoplasm of vertebrate rod photoreceptors, as well as numerical simulations fo the response to light of dark-adapted Salamander rods.

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Correction To "Breaking Of Thunderstorm-Generated Gravity Waves As A Source Of Short-Period Ducted Waves At Mesopause Altitudes", Jonathan B. Snively, Victor P. Pasko Jan 2004

Correction To "Breaking Of Thunderstorm-Generated Gravity Waves As A Source Of Short-Period Ducted Waves At Mesopause Altitudes", Jonathan B. Snively, Victor P. Pasko

Publications

No abstract provided.

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Ion Cyclotron Waves In The High Altitude Cusp: Cluster Observations At Varying Spacecraft Separations, K. Nykyri, P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh, B. Lavraud, I. Dandouras, H. Reme Dec 2003

Ion Cyclotron Waves In The High Altitude Cusp: Cluster Observations At Varying Spacecraft Separations, K. Nykyri, P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh, B. Lavraud, I. Dandouras, H. Reme

Publications

We have analysed high-resolution Cluster magnetic field data during three high-altitude cusp crossings in 2001 and 2002. The Cluster separations for these crossings varied between 100 and 600 km and therefore provided an unique opportunity to study wave properties at different length scales. In the cusp Cluster sees frequent intervals of magnetic field fluctuations with clear peaks in power close to the local ion cyclotron frequency, and both left- and right-handed polarisations. At large separations the power seen at different spacecraft can differ by orders of magnitude. For smaller separations, the power seen at the four spacecraft agrees better but …

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Breaking Of Thunderstorm-Generated Gravity Waves As A Source Of Short-Period Ducted Waves At Mesopause Altitudes, Jonathan B. Snively, Victor P. Pasko Dec 2003

Breaking Of Thunderstorm-Generated Gravity Waves As A Source Of Short-Period Ducted Waves At Mesopause Altitudes, Jonathan B. Snively, Victor P. Pasko

Publications

Numerical simulation results indicate that the breaking of atmospheric gravity waves generated by tropospheric convection can excite short-period secondary waves, which are trapped in the lower thermospheric duct and which closely resemble quasi-monochromatic structures commonly observed in airglow imaging experiments.

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Using Optical And Near-Infrared Photometry To Test Macho Lens Candidates, Ted Von Hippel, Et Al. Oct 2003

Using Optical And Near-Infrared Photometry To Test Macho Lens Candidates, Ted Von Hippel, Et Al.

Publications

We obtained new VLT/ISAAC H-band observations for five MACHO LMC source stars and adjacent LMC field regions. After combining our near-IR photometry with Hubble Space Telescope/PC BVRI optical photometry, we compared the MACHO objects to the adjacent field stars in a variety of color-magnitude and color-color diagrams. These diagnostic diagrams were chosen to be sensitive to our hypothesis that at least some of the MACHO lenses were foreground Galactic disk or thick-disk M dwarfs. For the five lensed objects we studied, our hypothesis could be ruled out for main-sequence lens masses ≥0.1 M☉ for distances out to …

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Constraining The Evolution Of Zz Ceti, Anjum S. Mukadam, S. O. Kepler, D. E. Nather, M. Kilic, F. Mullally, T. Von Hippel, S. J. Kleinman, A. Nitta, J. A. Guzik, P. A. Bradley, J. Matthews, K. Sekiguchi, D. J. Sullivan, T. Sullivan, R. R. Shobbrook, P. Birch, X. J. Jiang, D. W. Xu, S. Joshi, B. N. Ashoka, P. Ibbetson, E. Leibowitz, E. O. Ofek, E. G. Meištas, R. Janulis, R. D. Ališauskas, R. Kalytis, G. Handler, D. Kilkenny, D. O'Donoghue, D. W. Kurtz, M. Müller, P. Moskalik, W. Ogloza, S. Zola, J. Krzesiński, F. Johnannessen, J. M. Gonzalez-Perez, J. E. Solheim, R. Silvotti, S. Bernabei, G. Vauclair, N. Dolez, J. N. Fu, M. Chevreton, M. Manteiga, O. Suárez, A. Ulla, M. S. Cunha, T. S. Metcalfe, A. Kanaan, L. Fraga, A. F. M. Costa, O. Giovannini, G. Fontaine, P. Bergeron, M. S. O'Brien, D. Sanwal, M. A. Wood, T. J. Ahrens, N. Silvestri, E. W. Klumpe, S. D. Kawaler, R. Riddle, M. D. Reed, T. K. Watson Sep 2003

Constraining The Evolution Of Zz Ceti, Anjum S. Mukadam, S. O. Kepler, D. E. Nather, M. Kilic, F. Mullally, T. Von Hippel, S. J. Kleinman, A. Nitta, J. A. Guzik, P. A. Bradley, J. Matthews, K. Sekiguchi, D. J. Sullivan, T. Sullivan, R. R. Shobbrook, P. Birch, X. J. Jiang, D. W. Xu, S. Joshi, B. N. Ashoka, P. Ibbetson, E. Leibowitz, E. O. Ofek, E. G. Meištas, R. Janulis, R. D. Ališauskas, R. Kalytis, G. Handler, D. Kilkenny, D. O'Donoghue, D. W. Kurtz, M. Müller, P. Moskalik, W. Ogloza, S. Zola, J. Krzesiński, F. Johnannessen, J. M. Gonzalez-Perez, J. E. Solheim, R. Silvotti, S. Bernabei, G. Vauclair, N. Dolez, J. N. Fu, M. Chevreton, M. Manteiga, O. Suárez, A. Ulla, M. S. Cunha, T. S. Metcalfe, A. Kanaan, L. Fraga, A. F. M. Costa, O. Giovannini, G. Fontaine, P. Bergeron, M. S. O'Brien, D. Sanwal, M. A. Wood, T. J. Ahrens, N. Silvestri, E. W. Klumpe, S. D. Kawaler, R. Riddle, M. D. Reed, T. K. Watson

Publications

We report our analysis of the stability of pulsation periods in the DAV star (pulsating hydrogen atmosphere white dwarf) ZZ Ceti, also called R548. On the basis of observations that span 31 years, we conclude that the period 213.13 s observed in ZZ Ceti drifts at a rate dP/dt ≤ (5:5 ± 1:9) x 10-15 s s-1, after correcting for proper motion. Our results are consistent with previous Ṗ values for this mode and an improvement over them because of the larger time base. The characteristic stability timescale implied for the pulsation period is …

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Supernova Reverse Shocks: Sic Growth And Isotopic Composition, Ethan A-N. Deneault, Donald D. Clayton, Alexander Heger Sep 2003

Supernova Reverse Shocks: Sic Growth And Isotopic Composition, Ethan A-N. Deneault, Donald D. Clayton, Alexander Heger

Publications

We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t ¼ 106 s, reverse shock from the presupernova wind near 108–109 s, and reverse shock from the interstellar medium near 1010 s. Using one-dimensional hydrodynamics we show that the first creates a dense shell of Si and C atoms near 106 s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated …

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Book Review: Observer's Guide To Stellar Evolution: The Birth, Life, And Death Of Stars, T. D. Oswalt Sep 2003

Book Review: Observer's Guide To Stellar Evolution: The Birth, Life, And Death Of Stars, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Observer's Guide to Stellar Evolution : the Birth, Life, and Death of Stars by Mike Inglis. Springer, 2003 236p, 1-85233-465-7 $44.95

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Computational Models For Diffusion Of Second Messengers In Visual Transduction, Harihar Khanal Aug 2003

Computational Models For Diffusion Of Second Messengers In Visual Transduction, Harihar Khanal

Publications

The process of phototransduction, whereby light is converted into an electrical response in retinal rod and cone photoreceptors, involves, as a crucial step, the diffusion of cytoplasmic signaling molecules, termed second messengers. A barrier to mathematical and computational modeling is the complex geometry of the rod outer segment which contains about 1000 thin discs. Most current investigations on the subject assume a well-stirred bulk aqueous environment thereby avoiding such geometrical complexity. We present theoretical and computational spatio-temporal models for phototransduction in vertebrate rod photoreceptors, which are pointwise in nature and thus take into account the complex geometry of the …

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Multisite Observations Of The Pms Δ Delta Scuti Star V351 Ori, V. Ripepi, Terry D. Oswalt, M. Marconi, S. Bernabei, Et Al. Jun 2003

Multisite Observations Of The Pms Δ Delta Scuti Star V351 Ori, V. Ripepi, Terry D. Oswalt, M. Marconi, S. Bernabei, Et Al.

Publications

We present the results of multisite observations spanning two years on the pre–main-sequence (PMS) star V351 Ori. A total of around 180 hours of observations over 29 nights have been collected, allowing us to measure five different periodicities, most likely related to the Scuti variability of V351 Ori. Comparison with the predictions of linear nonadiabatic radial pulsation models put stringent constraints on the stellar parameters and indicate that the distance to V351 Ori is intermediate between the lower limit measured by Hipparcos (210 pc) and that of the Orion Nebula (450 pc). However, radial pulsation models are unable to reproduce …

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Ampnet - A Highly Available Cluster Interconnection Network, Amy Apon, Larry Bilbur Apr 2003

Ampnet - A Highly Available Cluster Interconnection Network, Amy Apon, Larry Bilbur

Publications

No abstract provided.

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Book Review: Strange Matters: Undiscovered Ideas At The Frontiers Of Space And Time, T. D. Oswalt Mar 2003

Book Review: Strange Matters: Undiscovered Ideas At The Frontiers Of Space And Time, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Strange Matters: Undiscovered Ideas at the Frontiers of Space and Time by Tom Siegfried. John Henry, 2002 307p, 0-309-08407-5 $24.95.

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Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss Jan 2003

Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss

Publications

Ground magnetometer measurements of total magnetic field strength from 6 stations at low latitudes were analyzed using power spectrum and Hurst range scaling techniques. The Hurst exponents for most of these time-series were near 0.5, which indicates stochasticity, with the highest latitude stations exhibiting some persistence with Hurst exponents greater than 0.6. Although no definite correlations are evident, the relative increase of the Hurst exponent with latitude suggests the possibility that the underlying dynamics of the magnetosphere change with latitude. This result may help quantify the dynamics of the inner magnetosphere itself without the direct presence of the solar wind …

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The Local-Time Variation Of The Quiet Plasmasphere: Geosynchronous Observations And Kinetic Theory, Mark Anthony Reynolds, G. Ganguli, Y-J Su, M.F. Thomsen Jan 2003

The Local-Time Variation Of The Quiet Plasmasphere: Geosynchronous Observations And Kinetic Theory, Mark Anthony Reynolds, G. Ganguli, Y-J Su, M.F. Thomsen

Publications

The quiet-time structure of the plasmaspheric density was investigated using observations of the Los Alamos geosynchronous satellites, and these observations were compared with theoretical predictions of the quasi-static localtime variation by a kinetic model. It was found that the coupling to the ionosphere (via the local-time variation of the exobase) played a key role in determining the density structure at 6.6 RE. The kinetic model predicts that most of the local-time variation at geosynchronous orbit is due to the variation of the exobase parameters. During quiet times, when the convection electric field is dominated by the corotation field, the effects …

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Intergalactic Globular Clusters, Michael J. West, Ted Von Hippel, Patrick Cote, Henry C. Ferguson, Michael D. Gregg, Andres Jordan, Ronald O. Marzke, Nial R. Tanvir Jan 2003

Intergalactic Globular Clusters, Michael J. West, Ted Von Hippel, Patrick Cote, Henry C. Ferguson, Michael D. Gregg, Andres Jordan, Ronald O. Marzke, Nial R. Tanvir

Publications

We confirm and extend our previous detection of a popula- tion of intergalactic globular clusters in Abell 1185, and report the first discovery of an intergalactic globular cluster in the nearby Virgo cluster of galaxies. The numbers, colors and luminosities of these objects can place constraints on their origin, which in turn may yield new insights to the evolution of galaxies in dense environments.

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A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown Dec 2002

A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown

Publications

We use gravity wave parameters derived from the ALOHA-93 campaign to model four gravity waves in airglow emissions as observed from the ground to numerically predict whether these waves could have been observed from space. In spite of encountering critical levels, some waves may still be observed in the airglow provided the critical level lies within the airglow emission region. One of the four waves experiences a critical level in the lower region of an airglow layer such that the disturbance to the volume emission rate would be effectively limited to a short distance along a satellite line of sight. …

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