Bulletin of the American Physical Society
Joint Fall 2011 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 56, Number 7
Thursday–Saturday, October 6–8, 2011; Commerce, Texas
Session L8: Astronomy, Astrophysics and Space Station III |
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Chair: Mustapha Ishak-Boushaki, University of Texas at Dallas Room: Sam Rayburn Center Second Floor, Pride Room |
Saturday, October 8, 2011 9:25AM - 9:37AM |
L8.00001: Modeling of Optical Resonators Using Gaussian Beams and Ray Tracing Techniques Liliana Ruiz, Sergio Cantu, Volker Quetschke, Malik Rakhmanov One of the main components in the laser stabilization subsystem in the Laser Interferometer Gravitational-Wave Observatory (LIGO) is a triangular ring resonator, which filters out high order Hermite-Gaussian modes in the laser beam. We developed a model to study the optical properties of such resonators and investigate their performance. The propagation of the laser beam is modeled by combining ray tracing techniques with wave optics. The model can be used to analyze various effects due to mirror misalignments and fluctuations of the laser beam pointing. [Preview Abstract] |
Saturday, October 8, 2011 9:37AM - 9:49AM |
L8.00002: Solar EUV irradiance and geomagnetic energy variation during last solar cycle Yanshi Huang, Yue Deng The record-low thermospheric density during last solar minimum has been reported and it has been mainly explained as the consequence of the anomalously low solar extreme ultraviolet (EUV) irradiance. However, relative little attention has been paid to the variation of geomagnetic energy. The geomagnetic energy is dissipated into upper atmosphere by Joule heating and particle precipitation. In this study, to understand and explain the anomalously low density during the solar minimum 23/24, we examine the energy budget to the Earth's upper atmosphere from solar EUV irradiance, Joule heating and particle precipitation heating from 1995 to 2010. The solar EUV power is derived using the latest version of SOLAR2000 solar irradiance specification model and also from the measurement of SOHO/SEM. The empirical model Weimer05 is used to derive the globally integrated joule heating power. The global hemispheric power data is collected from NOAA to show the variation of particle precipitation heating. The variation of different energy inputs and their significance to the neutral density will be discussed. [Preview Abstract] |
Saturday, October 8, 2011 9:49AM - 10:01AM |
L8.00003: Birkeland currents during the Whole Heliosphere Interval for the Carrington Rotation 2068 Kevin Pham, Ramon Lopez, Robert Bruntz, Yue Deng, Yanshi Huang The Whole Heliosphere Interval (WHI), encompassing Carrington Rotation 2068 (March 20 -- April 16, 2008), has been extensively studied through both observations and simulations. The Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic simulation was run for the duration of the WHI with a variety of inputs and then the Birkeland currents for each run were analyzed. The Birkeland currents are currents that flow along the Earth's magnetic field, connecting the magnetosphere to the high latitude ionosphere. A comparison of the Birkeland currents from the LFM runs will be discussed in detail. [Preview Abstract] |
Saturday, October 8, 2011 10:01AM - 10:13AM |
L8.00004: Computation of Collision-Induced Absorption by dense Hydrogen-Helium gas mixtures up to Thousands of Kelvin, for Astrophysical Applications Martin Abel, Lothar Frommhold, Xiaoping Li, Katharine L. C. Hunt The interaction-induced absorption by collisional pairs of H$_{2}$ molecules is an important opacity source in the atmospheres of the outer planets and cool stars. The emission spectra of cool white dwarf stars differ significantly in the infrared from the expected blackbody spectra of their cores, which is largely due to absorption by collisional H$_{2}$- -H$_{2}$, H$_{2}$--He, and H$_{2}$--H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin, as required, for example, in astrophysical analyses of objects, including cool white dwarf stars, brown dwarf stars, M dwarfs, cool main sequence stars, solar and extra-solar planets, and the formation of so-called first stars [1]. Comparisons of our calculations with laboratory measurements, which exist only at room temperature and below, show close agreement. \\[4pt] [1] Martin Abel, Lothar Frommhold, Xiaoping Li, and Katharine L. C. Hunt, ``Collision-Induced Absorption by H$_{2}$ pairs: From Hundreds to Thousands of Kelvin'', J. Phys. A, 2011, 115 (25), pp 6805-6812 [Preview Abstract] |
Saturday, October 8, 2011 10:13AM - 10:25AM |
L8.00005: Kiloparsec-scale Jets in Lobe-dominated Quasars David Hough, Gareth Jones We are investigating the physics of kiloparsec-scale jets in a complete sample of lobe-dominated quasars (LDQs). Previously, Bridle et al. (1994, AJ, 108,766) reported results for 13 of the 25 LDQs in a well-defined 3CR complete sample. Here, we add results for 8 more LDQs, and present new analyses for all 21 sources (84\% completeness). Two key, but tentative, results in Bridle et al. are confirmed here: (1) the prominences (normalized brightnesses) of the parsec-scale and kiloparsec-scale jets are strongly correlated (99.9\% confidence), and (2) the prominence of the kpc jet terminal hot spots is anti-correlated with jet bending angle (99\% confidence, but this result is highly dependent on just 3 sources). Because relativistic motion has been directly observed in Doppler-boosted pc jets, the first result strongly suggests relativistic motion on kpc scales. The second result suggests that highly-bent kpc jets are less able to form powerful hot spots. Future work will explore longitudinal and transverse velocity fields in the kpc jets, as well as inverse Compton models for their X-ray emission. [Preview Abstract] |
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