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Aerospace, Physics, and Space Science Faculty Publications

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2013

Articles 1 - 30 of 38

Full-Text Articles in Physical Sciences and Mathematics

Uncovering The Deeply Embedded Active Galactic Nucleus Activity In The Nuclear Regions Of The Interacting Galaxy Arp 299, A Alonso-Herrero, Eric S. Perlman Dec 2013

Uncovering The Deeply Embedded Active Galactic Nucleus Activity In The Nuclear Regions Of The Interacting Galaxy Arp 299, A Alonso-Herrero, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

We present mid-infrared (MIR) 8-13 μm spectroscopy of the nuclear regions of the interacting galaxy Arp 299 (IC 694+NGC 3690) obtained with CanariCam (CC) on the 10.4 m Gran Telescopio Canarias (GTC). The high angular resolution (∼0.″3-0.″6) of the data allows us to probe nuclear physical scales between 60 and 120 pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded active galactic nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC 3690/Arp 299-B1 can be explained as emission from AGN-heated dust in …

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Measurement Of The Differential And Double-Differential Drell-Yan Cross Sections In Proton-Proton Collisions At S√ = 7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva Dec 2013

Measurement Of The Differential And Double-Differential Drell-Yan Cross Sections In Proton-Proton Collisions At S√ = 7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva

Aerospace, Physics, and Space Science Faculty Publications

Measurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5 (4.8) fb−1 in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at s" role="presentation" style="box-sizing: inherit; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">s√� = 7 TeV. The measured inclusive cross section in the Z-peak region (60–120 GeV) is σ(ℓℓ) = 986.4 ± 0.6 (stat.) ± 5.9 (exp. …

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Direct Observations Of Plasma Upflows And Condensation In A Catastrophically Cooling Solar Transition Region Loop, Norton B. Orange, David L. Chesney, Hakeem M. Oluseyi, Katie Hesterly, M Patel, Patrick Champey Dec 2013

Direct Observations Of Plasma Upflows And Condensation In A Catastrophically Cooling Solar Transition Region Loop, Norton B. Orange, David L. Chesney, Hakeem M. Oluseyi, Katie Hesterly, M Patel, Patrick Champey

Aerospace, Physics, and Space Science Faculty Publications

Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models as well as their description of bright TR emission. Using the EUV Imaging Spectrometer on boardHinode, we observe fast upflows (vλ −10 km s−1) over multiple TR temperatures (5.8 logT 6.0) at the footpoint sites of a cool loop (logT 6.0). Prior to cool loop energizing, asymmetric flows of + 5 km s−1 and −60 km s−1 are observed at footpoint sites. These flows, speeds, and patterns occur simultaneously with both magnetic …

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Measurement Of The Cross Section And Angular Correlations For Associated Production Of A Z Boson With B Hadrons In Pp Collisions At S√ = 7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva Dec 2013

Measurement Of The Cross Section And Angular Correlations For Associated Production Of A Z Boson With B Hadrons In Pp Collisions At S√ = 7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva

Aerospace, Physics, and Space Science Faculty Publications

A study of proton-proton collisions in which two b hadrons are produced in association with a Z boson is reported. The collisions were recorded at a centre-of-mass energy of 7 TeVwith the CMS detector at the LHC, for an integrated luminosity of 5.2 fb−1. The b hadrons are identified by means of displaced secondary vertices, without the use of reconstructed jets, permitting the study of b-hadron pair production at small angular separation. Differential cross sections are presented as a function of the angular separation of the b hadrons and the Z boson. In addition, inclusive measurements are presented. …

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Non-Potential Fields In The Quiet Sun Network: Extreme-Ultraviolet And Magnetic Footpoint Observations, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange Nov 2013

Non-Potential Fields In The Quiet Sun Network: Extreme-Ultraviolet And Magnetic Footpoint Observations, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange

Aerospace, Physics, and Space Science Faculty Publications

The quiet Sun (QS) magnetic network is known to contain dynamics which are indicative of non-potential fields. Non-potential magnetic fields forming “S-shaped” loop arcades can lead to the breakdown of static activity and have only been observed in high temperature X-ray coronal structures—some of which show eruptive behavior. Thus, analysis of this type of atmospheric structuring has been restricted to large-scale coronal fields. Here we provide the first identification of non-potential loop arcades exclusive to the QS supergranulation network. High-resolution Atmospheric Imaging Assembly data from the Solar Dynamics Observatory have allowed for the first observations of fine-scale “S-shaped” loop arcades …

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New Insights Into The Study Of Magnetic Field In The Clumpy Torus Of Agn Using Near-Infrared Polarimetry, Enrique Lopez-Rodriguez, Christopher C. Packham, Stuart Young, Moshe Elitzur, Nancy A. Levenson, Rachel E. Mason, Christina Ramos Almeida, Almudena Alonso-Herrero, Terry J. Jones, Eric S. Perlman Oct 2013

New Insights Into The Study Of Magnetic Field In The Clumpy Torus Of Agn Using Near-Infrared Polarimetry, Enrique Lopez-Rodriguez, Christopher C. Packham, Stuart Young, Moshe Elitzur, Nancy A. Levenson, Rachel E. Mason, Christina Ramos Almeida, Almudena Alonso-Herrero, Terry J. Jones, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

We present J, H and K., imaging polarimetry of IC5063. N1R polarimetry observations may advance our understanding of the mechanisms of polarisation and hence magnetic field strength in the torus of AGN. In these proceedings we summarize the polarisation results of the central 1.2" aperture (̃263 pc) of IC5063. We present a simple polarising model to account for various mechanisms of polarisation in the central regions of IC5063. The model is consistent with dichroic absorption from diffuse stellar emission through dust in the nuclear bulge and electron scattering as dominant mechanisms of polarisation at J and H. Dichroic absorption from …

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The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul Oct 2013

The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

The focused transport theory is appropriate to describe the injection and acceleration of low-energy particles at shocks as an extension of diffusive shock acceleration (DSA). In this investigation, we aim to characterize the role of cross-shock potential (CSP) originated in the charge separation across the shock ramp on pickup ion (PUI) acceleration at various types of shocks with a focused transport model. The simulation results of energy spectrum and spatial density distribution for the cases with and without CSP added in the model are compared.With sufficient acceleration time, the focused transport acceleration finally falls into the DSA regime with the …

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X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa Oct 2013

X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Qb, taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of LX = 4.3×1038 erg s−1 and Lbol/LEdd = 6.9×10−6, respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.

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Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi Oct 2013

Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi

Aerospace, Physics, and Space Science Faculty Publications

We describe the construction of a highly reliable sample of ∼7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg2 of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is severalmagnitudes fainter than most other wide-angle surveys; the photometric errors range from ∼0.03 mag at r = 15 to ∼0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about …

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A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt Sep 2013

A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt

Aerospace, Physics, and Space Science Faculty Publications

The relations observed between supermassive black holes and their host galaxies suggest a fundamental link in the processes that cause these two objects to evolve. A more comprehensive understanding of these relations could be gained by increasing the number of supermassive black hole mass (M•) measurements. This can be achieved, in part, by continuing to model the stellar dynamics at the centers of galactic bulges using data of the highest possible spatial resolution. Consequently, we present here an atlas of galaxies in the Space Telescope Imaging Spectrograph (STIS) data archive that may have spectra suitable for new M• estimates. Archived …

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Inclusive Search For Supersymmetry Using Razor Variables In Pp Collisions At √S=7 Tev, S. A. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. R. Tumasyan, W. Adam, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, H Kalakhety, Igor Vodopiyanov Aug 2013

Inclusive Search For Supersymmetry Using Razor Variables In Pp Collisions At √S=7 Tev, S. A. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. R. Tumasyan, W. Adam, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, H Kalakhety, Igor Vodopiyanov

Aerospace, Physics, and Space Science Faculty Publications

An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb -1 of integrated luminosity. The selected events are analyzed in the 2D razor space of MR, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number of events beyond that predicted by the standard model. …

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Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman Aug 2013

Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under active debate, including synchrotron radiation, inverse-Comptonized cosmic microwave background (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high-resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136−135 obtained with the Hubble …

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Exploring The Variable Sky With Linear. Ii. Halo Structure And Substructure Traced By Rr Lyrae Stars To 30 Kpc, Branimir Sesar, Hakeem Oluseyi Aug 2013

Exploring The Variable Sky With Linear. Ii. Halo Structure And Substructure Traced By Rr Lyrae Stars To 30 Kpc, Branimir Sesar, Hakeem Oluseyi

Aerospace, Physics, and Space Science Faculty Publications

We present a sample of ∼5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over ∼8000 deg2 of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of ∼4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, …

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The Impact Of Bars On Disk Breaks As Probed By S⁴G Imaging, Juan Carlos Muñoz-Mateos, Trisha Mizusawa Jul 2013

The Impact Of Bars On Disk Breaks As Probed By S⁴G Imaging, Juan Carlos Muñoz-Mateos, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6μm images from the Spitzer Survey of Stellar Structure in Galaxies. In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single-exponential profile have a scale length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the particular case of barred galaxies, the ratio between the break …

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Searches For Long-Lived Charged Particles In Pp Collisions At S√ =7 And 8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva Jun 2013

Searches For Long-Lived Charged Particles In Pp Collisions At S√ =7 And 8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva

Aerospace, Physics, and Space Science Faculty Publications

Results of searches for heavy stable charged particles produced in pp collisions at s" role="presentation" style="box-sizing: inherit; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">s√� = 7 and 8 TeV are presented corresponding to an integrated luminosity of 5.0 fb−1 and 18.8 fb−1, respectively. Data collected with the CMS detector are used to study the momentum, energy deposition, and time-of-flight of signal candidates. Leptons with an electric charge between e/3 and 8e …

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70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao Jun 2013

70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao

Aerospace, Physics, and Space Science Faculty Publications

We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6 M⊙, which is consistent with prior work in the literature. The distances of these WDs are estimated using the …

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Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel May 2013

Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel

Aerospace, Physics, and Space Science Faculty Publications

We report the discovery and confirmation of a transiting circumbinary planet (PH1b) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ∼137 days, with seven transits identified in Quarters 1–11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities …

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Tracers Of Chromospheric Structure.I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J K. Zhao, Terry D. Oswalt, G Zhao, Q H. Lu, A L. Luo, L Y. Zhang May 2013

Tracers Of Chromospheric Structure.I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J K. Zhao, Terry D. Oswalt, G Zhao, Q H. Lu, A L. Luo, L Y. Zhang

Aerospace, Physics, and Space Science Faculty Publications

We present chromospheric activity index SHK measurements for over 13,000 F, G, and K disk stars with high signal-to-noise ratio (>60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter δS is defined as the difference between SHK and a “zero” emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low-resolution spectra. Cooler stars are generally more active and display a larger scatter than hotter stars. Stars …

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Observation Of A New Boson With Mass Near 125 Gev In Pp Collisions At S√=7 And 8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva May 2013

Observation Of A New Boson With Mass Near 125 Gev In Pp Collisions At S√=7 And 8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Francisco Yumiceva

Aerospace, Physics, and Space Science Faculty Publications

A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb−1 at s=7" role="presentation" style="box-sizing: inherit; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">s√=7�=7 TeV, and up to 5.3 fb−1 at s=8" role="presentation" style="box-sizing: inherit; display: inline; line-height: …

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Acceleration Of Low-Energy Ions At Parallel Shocks With A Focused Transport Model, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul Apr 2013

Acceleration Of Low-Energy Ions At Parallel Shocks With A Focused Transport Model, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

We present a test particle simulation on the injection and acceleration of low-energy suprathermal particles by parallel shocks with a focused transport model. The focused transport equation contains all necessary physics of shock acceleration, but avoids the limitation of diffusive shock acceleration (DSA) that requires a small pitch angle anisotropy. This simulation verifies that the particles with speeds of a fraction of to a few times the shock speed can indeed be directly injected and accelerated into the DSA regime by parallel shocks. At higher energies starting from a few times the shock speed, the energy spectrum of accelerated particles …

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Transport Of Solar Energetic Particles Accelerated By Icme Shocks: Reproducing The Reservoir Phenomenon, Gang Qin, Y Wang, Ming Zhang, Silvia Dalla Apr 2013

Transport Of Solar Energetic Particles Accelerated By Icme Shocks: Reproducing The Reservoir Phenomenon, Gang Qin, Y Wang, Ming Zhang, Silvia Dalla

Aerospace, Physics, and Space Science Faculty Publications

In this work, gradual solar energetic particle (SEP) events observed by multiple spacecraft are investigated with model simulations. Based on a numerical solution of the Fokker-Planck focused transport equation including perpendicular diffusion of particles, we obtained the fluxes of SEPs accelerated by an interplanetary coronal mass ejection driven shock as it propagates outward through the three-dimensional Parker interplanetary magnetic field. The shock is treated as a moving source of energetic particles with an assumed particle distribution function. We look at the time profiles of particle flux as they are observed simultaneously by multiple spacecraft located at different locations. The dependence …

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Search For New Physics In Events With Same-Sign Dileptons And B Jets In Pp Collisions At S√=8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Igor Vodopiyanov, Francisco Yumiceva Mar 2013

Search For New Physics In Events With Same-Sign Dileptons And B Jets In Pp Collisions At S√=8 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Igor Vodopiyanov, Francisco Yumiceva

Aerospace, Physics, and Space Science Faculty Publications

A search for new physics is performed using events with isolated same-sign leptons and at least two bottom-quark jets in the final state. Results are based on a sample of proton-proton collisions collected at a center-of-mass energy of 8 TeV with the CMS detector and corresponding to an integrated luminosity of 10.5 fb−1. No excess above the standard model background is observed. Upper limits are set on the number of events from non-standard-model sources and are used to constrain a number of new physics models. Information on acceptance and efficiencies is also provided so that the results can …

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Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen Feb 2013

Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen

Aerospace, Physics, and Space Science Faculty Publications

To understand the behavior of cosmic-ray modulation seen by the two Voyager spacecraft in the region near the termination shock (TS) and in the heliosheath at a distance of >100 AU, a realistic magnetohydrodynamic global heliosphere model is incorporated into our cosmic-ray transport code, so that the detailed effects of the heliospheric boundaries and their plasma/magnetic geometry can be revealed. A number of simulations of cosmic-ray modulation performed with this code result in the following conclusions. (1) Diffusive shock acceleration by the TS can significantly affect the level of cosmic-ray flux and, in particular, its radial gradient profile in the …

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Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang Feb 2013

Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f ∝ p −5,which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V0 and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the …

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Search For Exotic Resonances Decaying Into Wz/Zz In Pp Collisions At S√=7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Igor Vodopiyanov Feb 2013

Search For Exotic Resonances Decaying Into Wz/Zz In Pp Collisions At S√=7 Tev, The Cms Collaboration, S. Chatrchyan, V. Khachatryan, Marc M. Baarmand, B. Dorney, Marcus Hohlmann, Himali Kalakhety, Igor Vodopiyanov

Aerospace, Physics, and Space Science Faculty Publications

A search for new exotic particles decaying to the VZ final state is performed, where V is either a W or a Z boson decaying into two overlapping jets and the Z decays into a pair of electrons, muons or neutrinos. The analysis uses a data sample of pp collisions corresponding to an integrated luminosity of 5 fb−1 collected by the CMS experiment at the LHC at s=7" role="presentation" style="box-sizing: inherit; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; …

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2006 May–July Major Radio Flare Episodes In Cygnus X-3: Spectrotiming Analysis Of The X-Ray Data, K. I. I. Koljonen, M. L. Mccollough, D. C. Hannikainen, R. Droulans Feb 2013

2006 May–July Major Radio Flare Episodes In Cygnus X-3: Spectrotiming Analysis Of The X-Ray Data, K. I. I. Koljonen, M. L. Mccollough, D. C. Hannikainen, R. Droulans

Aerospace, Physics, and Space Science Faculty Publications

We analyse in detail the X-ray data of the microquasar Cygnus X-3 obtained during major radio flaring episodes in 2006 with multiple observatories. The analysis consists of two parts: probing the fast (∼1min) X-ray spectral evolution with principal component analysis followed by subsequent spectral fits to the time-averaged spectra (∼3 ks). Based on the analysis we find that the overall X-ray variability during major flaring episodes can be attributed to two principal components whose evolution based on spectral fits is best reproduced by a hybrid Comptonization component and a bremsstrahlung or saturated thermal Comptonization component. The variability of the thermal …

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Modeling Terrestrial Gamma Ray Flashes Produced By Relativistic Feedback Discharges, Ningyu Liu, Joseph R. Dwyer Jan 2013

Modeling Terrestrial Gamma Ray Flashes Produced By Relativistic Feedback Discharges, Ningyu Liu, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

This paper reports a modeling study of terrestrial gamma ray flashes (TGFs) produced by relativistic feedback discharges. Terrestrial gamma ray flashes are intense energetic radiation originating from the Earth’s atmosphere that has been observed by spacecraft. They are produced by bremsstrahlung interactions of energetic electrons, known as runaway electrons, with air atoms. An efficient physical mechanism for producing large fluxes of the runaway electrons to make the TGFs is the relativistic feedback discharge, where seed runaway electrons are generated by positrons and X-rays, products of the discharge itself. Once the relativistic feedback discharge becomes self-sustaining, an exponentially increasing number of …

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Effects Of Different Geomagnetic Storm Drivers On The Ring Current: Crcm Results, W. Douglas Cramer, Niescja E. Turner, M. C. Fok, N. Yu Buzulukova Jan 2013

Effects Of Different Geomagnetic Storm Drivers On The Ring Current: Crcm Results, W. Douglas Cramer, Niescja E. Turner, M. C. Fok, N. Yu Buzulukova

Aerospace, Physics, and Space Science Faculty Publications

The storm-time magnetic disturbance at the Earth’s equator, as commonly measured by the Dst index, is induced by currents in the near-Earth magnetosphere. The ring current is generally considered the most important contributor, but other magnetospheric currents have also been found to have significant effects. Of the two main types of solar geomagnetic storm drivers, Coronal Mass Ejections (CMEs) tend to have a much greater impact on Dst than Corotating Interaction Regions (CIRs). Ring current models have been found to underestimate Dst, particularly during storms driven by CIRs. One possible explanation is that the models neglect to handle some aspect …

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Formation Of Sprite Streamers At Subbreakdown Conditions From Ionospheric Inhomogeneities Resembling Observed Sprite Halo Structures, Burcu C. Kosar, Ningyu Liu, Hamid K. Rassoul Jan 2013

Formation Of Sprite Streamers At Subbreakdown Conditions From Ionospheric Inhomogeneities Resembling Observed Sprite Halo Structures, Burcu C. Kosar, Ningyu Liu, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Modeling results of sprite streamer formation from large ionospheric inhomogeneities or patches (several tens to hundreds of meter wide) indicate that positive streamers can be initiated at subbreakdown conditions from the inhomogeneities with a density comparable to sprite halo densities. For spherical patches with a given radius, the minimum density required for streamer initiation decreases with increasing ambient field. For a given density, the minimum size of the inhomogeneity decreases with increasing ambient field. The modeling results on the associated optical emissions show that a luminous spherical-like cap appears around the lower tip of the ionization patch before streamer initiation, …

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The Angular Distribution Of Energetic Electron And X-Ray Emissions From Triggered Lightning Leaders, M. M. Schaal, Joseph R. Dwyer, Hamid K. Rassoul, Jonathan David Hill, Douglas M. Jordan, Martin A. Uman Jan 2013

The Angular Distribution Of Energetic Electron And X-Ray Emissions From Triggered Lightning Leaders, M. M. Schaal, Joseph R. Dwyer, Hamid K. Rassoul, Jonathan David Hill, Douglas M. Jordan, Martin A. Uman

Aerospace, Physics, and Space Science Faculty Publications

We investigate individual X-ray bursts from lightning leaders to determine if energetic electrons at the source (and hence X-rays) are emitted isotropically or with some degree of anisotropy. This study was motivated by the work of Saleh et al. (2009), which found the falloff of X-rays in concentric radial annuli, covering all azimuthal directions in each annulus, from the lightning channel to be most consistent with an isotropic electron source. Here we perform a statistical analysis of angular and spatial distributions of X-rays measured by up to 21 NaI/PMT detectors at the International Center for Lightning Research and Testing site …

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