Physics Commons^™

Self-Similar Nested Sequences On A Chaotic Attractor For Travelingwave Electrophoresis, Boyd F. Edwards

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Oscillating electric potentials are applied to interdigitated arrays of cylindrical electrodes above and below a stationary conducting viscous fluid. The phases of these potentials are chosen to produce a longitudinal traveling wave that traps high-mobility ions and partially traps intermediate-mobility ions in periodic and narrowband chaotic attractors with average velocities that are commensurate with the wave speed. Stable periodic attractors have periods up to 101 times the wave period. Incommensurate broadband chaotic attractors are described by one-dimensional iterated contact-angle return maps, which feature self-similar nested sequences that converge geometrically at unstable trapped orbits. Sequences of singular angles and sequences of …

Analysis And Modeling Of Ducted And Evanescent Gravity Waves Observed In The Hawaiian Airglow, D. B. Simkhada, J. B. Snively, Michael J. Taylor, S. J. Franke

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Short-period gravity waves of especially-small horizontal scale have been observed in the Maui, Hawaii airglow. Typical small-scale gravity wave events have been investigated, and intrinsic wave propagation characteristics have been calculated from simultaneous meteor radar wind measurements. Here we report specific cases where wave structure is significantly determined by the local wind structure, and where wave characteristics are consistent with ducted or evanescent waves throughout the mesopause region. Two of the documented events, exhibiting similar airglow signatures but dramatically different propagation conditions, are selected for simple numerical modeling case studies. First, a Doppler-ducted wave trapped within relatively weak wind flow …

Flight Experiments On The Effects Of Contamination On Electron Emission Of Materials, John R. Dennison, Joshua L. Hodges, Jeff Duce, Amberly Evans

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We report on a study of the effects of prolonged exposure to the space environment and of chargeenhanced contamination on the electron emission and resistivity of spacecraft materials. The State of Utah Space Environment & Contamination Study (SUSpECS) was deployed on the International Space Station (ISS) in March 2008 onboard the MISSE-6 payload during STS-123. The Materials International Space Station Experiment (MISSE-6) program is designed to characterize the performance of candidate new space materials over the course of its ~17 month exposure to the LEO environment, with a target return date of August 2009 on STS-127. Approximately 165 samples are …

Simultaneous Observations Of Equatorial F-Region Plasma Depletions Over Brazil During The Spread-F Experiment (Spreadfex), Pierre-Dominique Pautet, Michael J. Taylor, N. P. Chapagain, H. Takahashi, A. F. Medeiros, F. T. São Sabbas, D. C. Fritts

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From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx) in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers) covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU) all-sky CCD imager operated at S˜ao …

Electron Densities In The Lower Thermosphere From Guvi 135.6 Nm Tomographic Inversions In Support Of Spreadfex, F. Kamalabadi, J. Comberiate, Michael J. Taylor, Pierre-Dominique Pautet

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The SpreadFEx campaign was conducted with the goal of investigating potential neutral atmospheric dynamics influences in seeding plasma instabilities and bubbles extending to higher altitudes from September to November 2005, with primary measurements in Brazil. In this paper, we present the results of space-based UV and ground-based optical observations in support of this campaign. Specifically, we present multi-dimensional electron density images obtained tomographically from the 135.6 nm emissions measured by the GUVI instrument aboard the TIMED satellite that result from radiative recombination of O+ and compare those with the corresponding 630.0 nm OI images recorded in the Brazilian sector. The …

The First Frontier: High Altitude Ballooning As A Platform For Student Research Experiences In Science And Engineering, Shane L. Larson, John C. Armstrong, William A. Hiscock

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High altitude balloon platforms are ideal for providing hands-on research experiences for students in physics, atmospheric science, engineering, and other aerospace-related disciplines. We describe a basic high altitude balloon platform that can be constructed and operated by undergraduate students. The existing HARBOR and BOREALIS programs are used to illustrate some possible science and engineering research projects that students can pursue as part of a high-altitude flight program.

Core-Level Spectroscopy Of The Pd/W(110) Interface: Evidence Of Long-Range Pd-Island—Winteractions At Submonolayer Coverages, D. Mark Riffe, N. D. Shinn, B. Kim, K. J. Kim, T. H. Kang

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We have measured W 4f_7/2 core-level photoemission spectra from W(1 1 0) in the presence of Pd overlayers for coverages up to ∼1 pseudomorphic monolayer (ML). At coverages close to 0.05 ML a striking change in the W core-level spectrum is observed, which we interpret as indicating a long-range lateral effect of 2D Pd islands upon the W electronic structure in both the first and second W layers. As the coverage increases the long-range effect weakens and finally vanishes near 0.85 ML. Above this coverage the W spectra are typical for a W-based bimetallic interface, with the first-layer …

First Observation Of An Undular Mesospheric Bore In A Doppler Duct, J. Fechine, C. M. Wrasse, H. Takahashi, A. F. Medeiros, P. P. Batista, B. R. Clemesha, L. M. Lima, D. C. Fritts, B. Laughman, Michael J. Taylor, Pierre-Dominique Pautet, M. G. Mlynczak, J. M. Russell

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On 1 October 2005, during the SpreadFEx campaign, a distinct mesospheric bore was observed over S˜ao Jo˜ao do Cariri (7.4 S, 36.5 W), Brazil by using airglow allsky imagers. The event appeared both in the OI5577 and OH emissions, forming a well extended wave front which was followed by short waves from behind. Simultaneous wind and temperature data obtained by the meteor radar and the TIMED/SABER satellite instrument revealed that the bore event occurred during the Doppler ducting condition in the emission layers.

Simultaneous Observation Of Ionospheric Plasma Bubbles And Mesospheric Gravity Waves During The Spreadfex Campaign, H. Takahashi, Michael J. Taylor, Pierre-Dominique Pautet, A. F. Medeiros, D. Gobbi, C. M. Wrasse, J. Fechine, M. A. Abdu, I. S. Batista, E. R. De Paula, J. A.H. Sobral, D. Aruda, D. C. Fritts

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During the Spread F Experiment campaign, under NASA Living with a Star (LWS) program, carried out in the South American Magnetic Equator region from 22 September to 8 November 2005, two airglow CCD imagers, located at Cariri (7.4° S, 36.5° W, geomag. 11° S) and near Brasilia (14.8° S, 47.6° W, geomag. 10° S) were operated simultaneously and measured the equatorial ionospheric bubbles and their time evolution by monitoring the airglow OI 6300 intensity depletions. Simultaneous observation of the mesospheric OH wave structures made it possible to investigate the relationship between the bubble formation in the ionosphere and the gravity …

Sodium And Potassiumvapor Faraday Filters Re-Visited: Theory And Applications, S. D. Harrell, C. Y. She, Tao Yuan, D. A. Krueger, H. Chen, S. Chen, Z. L. Hu

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A complete theory describing the transmission of atomic vapor Faraday filters is developed. The dependence of the filter transmission on atomic density and external magnetic field strength, as well as the frequency dependence of transmission, are explained in physical terms. As examples, applications of the computed results to ongoing research to suppress sky background, thus allowing Na lidar operation under sunlit conditions, and to enable measurement of the density of mesospheric oxygen atoms are briefly discussed.

Temperature Dependence Of Radiation Induced Conductivity In Insulators, John R. Dennison, Jodie Gillespie, Joshua Hodges, Rc Hoffman, J. Abbott, Alan W. Hunt, Randy Spalding

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Thisstudy measures Radiation Induced Conductivity (RIC) of Low Density Polyethylene(LDPE) over temperatures ranging from ~110 K to ~350 K. RIC occurswhen incident ionizing radiation deposits energy and excites electrons intothe conduction band of insulators. Conductivity was measured when avoltage was applied across vacuum-baked, thin film LDPE polymer samplesin a parallel plate geometry. RIC was calculated as thedifference in sample conductivity under no incident radiation and underan incident ~4 MeV electron beam at low incident fluxes of10⁻⁴–10⁻¹ Gr/sec. The steady-state RIC was found to agree well withthe standard power law relation, _RIC = k_{RI …}

Characteristics Of Convective Sources Of Gravity Waves And Sprites Present In Satellite Ir Images During The Spreadfex 2005 Campaign, F. T. São Sabbas, V. T. Rampinelli, J. Santiago, P. Stamus, S. L. Vadas, D. C. Fritts, Michael J. Taylor, Pierre-Dominique Pautet, G. Dolif Neto, O. Pinto

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We developed a technique to identify and estimate the size, intensity, and Tropopause overshoot of thunderstorm convective cores expected to be significant sources of gravity waves. The work was based on GOES IR images of South America on the night of 30 September to 1 October and 25–26 October 2005, as part of the Spread F Experiment (SpreadFEx) in Brazil in 2005. We also characterized, for the first time, the convective activity of three small TLE producing thunderstorms that yielded 11 TLEs on 25–26 October 2005. The campaign occurred during the dry to wet season transition in central Brazil, marked …

Traveling-Wave Electrophoresis For Microfluidic Separations, Boyd F. Edwards, A. T. Timperman, R. Lloyd Carroll, K. Jo, J. M. Mease, J. E. Schiffbauer

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Models and microfluidic experiments are presented of an electrophoretic separation technique in which charged particles whose mobilities exceed a tunable threshold are trapped between the crests of a longitudinal electric wave traveling through a stationary viscous fluid. The wave is created by applying periodic potentials to electrode arrays above and below a microchannel. Predicted average velocities agree with experiments and feature chaotic attractors for intermediate mobilities.

Characteristics Of Mesospheric Gravity Waves Near The Magnetic Equator, Brazil, During The Spreadfex Campaign, Michael J. Taylor, Pierre-Dominique Pautet, A. F. Medeiros, R. Buriti, J. Fechine, D. C. Fritts, S. L. Vadas, H. Takahashi, F. T. São Sabbas

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As part of the SpreadFEx campaign, coordinated optical and radio measurements were made from Brazil to investigate the occurrence and properties of equatorial Spread F, and to characterize the regional mesospheric gravity wave field. All-sky image measurements were made from two sites: Brasilia and Cariri located ~10° S of the magnetic equator and separated by ~1500 km. In particular, the observations from Brasilia provided key data in relatively close proximity to expected convective sources of the gravity waves. High-quality image measurements of the mesospheric OH emission and the thermospheric OI (630 nm) emission were made during two consecutive new moon …

Symmetry Reduction Of Quasi-Free States, Charles G. Torre

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Given a group-invariant quasi-free state on the algebra of canonical commutation relations (CCR), we show how group averaging techniques can be used to obtain a symmetry-reduced CCR algebra and reduced quasi-free state. When the group is compact, this method of symmetry reduction leads to standard results which can be obtained using other methods. When the group is noncompact, the group averaging prescription relies on technically favorable conditions which we delineate. As an example, we consider symmetry reduction of the usual vacuum state for a Klein–Gordon field on Minkowski spacetime by a noncompact subgroup of the Poincaré group consisting of a …

Field Demonstration Of Simultaneous Wind And Temperaturemeasurements From 5to50 Km With A Na Double-Edge Magneto-Optic Filter In A Multi-Frequency Doppler Lidar, W. Huang, X. Chu, Johannes Wiig, Bo Tan, Chihoko Yamashita, Tao Yuan, J. Yue, S. D. Harrell, C. Y. She, B. P. Williams, J. S. Friedman, R. M. Hardesty

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We report the first (to our knowledge) field demonstration of simultaneous wind and temperature measurements with a Na double-edge magneto-optic filter implemented in the receiver of a three-frequency Na Doppler lidar. Reliable winds and temperatures were obtained in the altitude range of 10-45 km with 1 km resolution and 60 min integration under the conditions of 0.4 W lidar power and 75 cm telescope aperture. This edge filter with a multi-frequency lidar concept can be applied to other direct-detection Doppler lidars for profiling both wind and temperature simultaneously from the lower to the upper atmosphere.

Electrostatic Discharge In Spacecraft Materials, Jennifer Albretsen Roth

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Understanding the characteristics of electron beam bombardment that induce electrostatic discharge (ESD) of insulating materials is crucial to constructing an electrically stable spacecraft. A measurement system has been designed to determine the beam energy and charge flux densities at which typical spacecraft materials intended for the James Webb Space Telescope (JWST) undergo ESD. Because discharge events occur over time intervals ranging from nanoseconds to minutes, multiple detection methods were employed as charge was accumulated on a sample surface; these methods included monitoring of sample current and optical emissions from the sample surface. Each sample was also examined with optical microscopy …

Storm-Time Density Enhancements In The Middle Latitude Dayside Ionosphere, R. A. Heelis, Jan Josef Sojka, M. David, Robert W. Schunk

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Enhancements of the total electron content (TEC) in the middle-latitude dayside ionosphere have often been observed during geomagnetic storms. The enhancements can be as large as a factor of 2 or more, and many sightings of such structures have occurred over the United States. Here we investigate the effectiveness of an expanded convection electric field as a mechanism for producing such ionospheric enhancements. As a test case, we examine the storm period of 5–7 November 2001, for which observations from the DMSP F13 are used to drive the Time Dependent Ionospheric Model (TDIM). Our findings indicate that at favorable universal …

Removal Of Nonconstant Daily Variation By Means Of Wavelet And Functional Data Analysis, I. Maslova, P. Kokoszka, Jan Josef Sojka, L. Zhu

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We propose a novel approach based on wavelet and functional principal component analysis to produce a cleaner index of the intensity of the symmetric ring current. We use functional canonical correlations to show that the new approach more effectively extracts symmetric global features. The main result of our work is the construction of a new index, which is an improved version of the existing wavelet-based index (WISA) and the old Dst index, in which a constant daily variation is removed. Here, we address the fact that the daily component varies from day to day and construct a “cleaner” index by …

Characterizing The Lower Ionosphere With A Space - Weather - Aware Receiver Matrix, D. D. Rice, R. D. Hunsucker, J. V. Eccles, Jan Josef Sojka, J. W. Raitt, J. J. Brady

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Current ionospheric models are very good at specifying regular diurnal and seasonal variations of the E and F regions of the ionosphere. Less is known about the behavior of the D region, although progress has recently been made with models such as the Data-Driven D-Region (DDDR). However, significant departures from modeled behaviors are observed even during solar minimum conditions, due to complex ionospheric weather effects arising from both solar activity above and terrestrial atmospheric perturbations below. The D-region perturbations directly affect VLF communications, and also affect daytime absorption of frequencies from LF through HF. Perturbations in the E and F …

Plasmasphere And Upper Ionosphere Contributions And Corrections During The Assimilation Of Gps Slant Tec, D. C. Thompson, L. Scherliess, Jan Josef Sojka, Robert W. Schunk

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Total electron content (TEC) measurements from ground stations to Global Positioning System (GPS) satellites provide a rich source of information about the Earth's ionosphere. These data comprise a significant part of the typical data set used by various data ingestion and assimilation models of the ionosphere. For example, the Utah State University (USU) Global Assimilation of Ionospheric Measurements (GAIM) data assimilation model uses slant TEC, along with various other types of data, to obtain a global reconstruction of the ionosphere. There are presently two different USU GAIM models: the Gauss‐Markov Kalman Filter (GAIM‐GM), which is operational at the NASA Community …

A Frequency Agile, Distributed Sensor System To Address Space Weather Effects Upon Ionospherically Dependent Systems, D. D. Rice, J. V. Eccles, Jan Josef Sojka, J. W. Raitt, J. Brady, R. D. Hunsucker

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The outstanding problem faced by operational systems that utilize the ionosphere is that ionospheric weather variability is comparable to the ionospheric climate variability. However, the number of simultaneous measurements is orders of magnitude too few to resolve the weather scales that are impacting systems. We describe a prototype distributed array of affordable passive radio beacon monitors combined with a central data repository and a data-model analysis system called the Frequency-Agile Distributed Sensor System (FADSS). By monitoring signals from terrestrial VLF/HF radio beacons the FADSS tracks changes in the D, E, or F regions and makes appropriate modifications to the ionospheric …

Observations Of Ionospheric Heating During The Passage Of Solar Coronal Hole Fast Streams, Jan Josef Sojka, R. L. Mcpherron, A. P. Van Eyken, M. J. Nicolis, C. J. Heinselman, J. D. Kelley

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Using ionospheric temperature measurements made continuously by the Poker Flat Incoherent Scatter Radar (PFISR) and EISCAT Svalbard Radar (ESR) during the International Polar Year (IPY), we provide evidence for directly driven ionospheric heating associated with the solar wind corotating interaction region (CIR). Both ESR and PFISR operated almost continuously during the IPY, which began on 1 March 2007. During this period 55 CIR events occurred and when ISR observations were available during these events ionospheric heating was observed. This study is the first comprehensive observation of ionospheric heating by CIRs demonstrated through case study comparisons and statistically over the 1-year …

Detecting A Stochastic Gravitational-Wave Background: The Overlap Reduction Function, Lee Samuel Finn, Shane L. Larson, Joseph D. Romano

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Detection of a gravitational-wave stochastic background via ground or space-based gravitational-wave detectors requires the cross correlation of the response of two or more independent detectors. The cross correlation involves a frequency-dependent factor—the so-called overlap reduction function or Hellings-Downs curve—that depends on the relative geometry of each detector pair, i.e., the detector separations and the relative orientation of their antenna patterns (beams). An incorrect formulation of this geometrical factor has appeared in the literature, leading to incorrect conclusions regarding the sensitivity of proposed detectors to a stochastic gravitational-wave background. To rectify these errors and as a reference for future work we …

Bubble Behavior In Nucleate Boiling Experiment Aboard The Space Shuttle, Justin P. Koeln, Jeffrey C. Boulware, Heng Ban

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Boiling dynamics in microgravity need to be better understood before heat transfer systems based on boiling mechanism can be developed for space applications. This paper presents the results of a nucleate boiling experiment aboard Space Shuttle Endeavor (STS- 108). The experiment utilized nickel-chromium resistance wire to boil water in microgravity, and the data was recorded with a CCD camera and six thermistors. This data was analyzed to determine the behavior of bubble formation, detachment from the heating wire, and travel in the water with effects of drag on bubble movement. Bubbles were observed to be ejected from the wire, travel …

Core-Level Shifts At The Pt/W(110) Monolayer Bimetallic Interface, D. Mark Riffe, N. D. Shinn, B. Kim, K. J. Kim, T. H. Kang

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We have measured W and Pt 4f7/2 core-level photoemission spectra from interfaces formed by ultrathin Pt layers on W(110), completing our core-level measurements of W(110)-based bimetallic interfaces involving the group-10 metals Ni, Pd, and Pt. With increasing Pt coverage the sequence of W spectra can be described using three interfacial core-level peaks with binding-energy (BE) shifts (compared to the bulk) of −0.220 ± 0.015, −0.060 ± 0.015, and +0.110 ± 0.010 eV. We assign these features to 1D, 2D pseudomorphic (ps), and 2D closed-packed (cp) Pt phases, respectively. For ~1 ps ML the Pt 4f7/2 BE is 71.40 ± 0.02 …

Critical Level Interaction Of A Gravity Wave With Background Winds Driven By A Large-Scale Wave Perturbation, M. K. Ejiri, Michael J. Taylor, T. Nakamura, S. J. Franke

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As part of the Maui-Mesosphere and Lower Thermosphere program, data from the Utah State University Mesospheric Temperature Mapper (MTM) and the University of Illinois Meteor Wind Radar (MWR) have been used to investigate wave-driven dynamical interactions in the upper mesosphere at low latitudes. On 29 June 2003, short-period (20 min) gravity waves (GWs) were imaged in the MTM in the near-infrared OH and O2 airglow emissions for most of the night from 0700 to 1500 UT. The GWs were observed to disappear rapidly in the O2 data (peak altitude: 94 km) around 1400 UT but remained evident in the lower …

The Spread F Experiment (Spreadfex): Overview And Summary Of The Spread F Experiment (Spreadfex), D. C. Fritts, M. A. Abdu, B. R. Batista, I. S. Batista, P. P. Batista, R. Buriti, B. R. Clemesha, T. Dautermann, E. De Paula, B. J. Fechine, B. G. Fejer, D. Gobbi, J. Haase, F. Kamalabadi, B. Luughman, P. P. Lima, H. L. Liu, A. F. Medeiros, P. D. Pautet, D. M. Riggin, F. São Sabbas, J. H.A. Sobral, P. Stamus, H. Takahashi, Michael J. Taylor, S. L. Vadas, C. Wrasse

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The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in …

Overview And Summary Of The Spread F Experiment (Spreadfex), D. C. Fritts, M. A. Abdu, B. R. Batista, I. S. Batista, P. P. Batista, R. Buritii, B. R. Clemesha, J. Comberiate, T. Dautermann, E. De Paula, B. J. Fechine, B. G. Fejer, D. Gobbi, J. Haase, F. Kalamabadi, B. Laughman, P. P. Lima, H. L. Liu, A. Medeiros, Pierre-Dominique Pautet, F. Sao Sabbas, J. H.A. Sobral, P. Stamus, H. Takahashi, Michael J. Taylor, S. L. Vadas, C. Wrasse

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We provide here an overview of, and a summary of results arising from, an extensive experimental campaign (the Spread F Experiment, or SpreadFEx) performed from September to November 2005, with primary measurements in Brazil. The motivation was to define the potential role of neutral atmosphere dynamics, specifically gravity wave motions propagating upward from the lower atmosphere, in seeding Rayleigh-Taylor instability (RTI) and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures …

Characterization Of Electrical Materials Properties Related To Spacecraft Charging, John R. Dennison

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No abstract provided.