Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 55, Number 9
Friday–Saturday, October 15–16, 2010; Ogden, Utah
Session K1: Astrophysics, Stars and Planets |
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Chair: Stacy Palen, Weber State University Room: Ballroom C |
Saturday, October 16, 2010 11:30AM - 11:42AM |
K1.00001: Obliquity variations in stable, high-inclination planetary systems and the impact on the habitable zone John Armstrong, Rory Barnes, Shawn Domagal-Goldman We explore the impact of obliquity variations on planetary habitability in realistic systems with high mutual inclination. We first numerically integrate the orbital evolution with N-body simulations and verify stability on $10^8$ year timescales. We then calculate the obliquity variations induced by the orbital architecture on 1 Earth mass (terrestrial) planets at 1 AU around a solar-mass star. Finally, we run energy balance models (EBM) on the terrestrial planets to assess surface temperature, which we assume is a proxy for habitability. We present general trends in obliquity changes and evaluate those changes in terms of habitability. Finally, we explore the limits of the habitable zone for planets with dramatic obliquity variations by changing the terrestrial planet's semi-major axis via EBM calculations for $10^6$ years. [Preview Abstract] |
Saturday, October 16, 2010 11:42AM - 11:54AM |
K1.00002: The Rise of Active Region Flux Tubes in the Turbulent Solar Convective Envelope Maria Weber, Yuhong Fan, Mark Miesch We use a thin flux tube model in a rotating spherical shell of turbulent convective flows computed separately from an existing 3D global simulation to study how active region scale flux tubes rise buoyantly from the bottom of the convection zone to near the solar surface. We investigate initial toroidal flux tubes at the base of the convection zone with field strengths ranging from 15 kG to 100 kG at initial latitudes ranging from 2 to 40 degrees. We find that the dynamic evolution of the flux tube changes from magnetic buoyancy dominated to convection dominated as we decrease the initial field strength from 100 kG to 15 kG. The mean properties of the final emerging loops with an initial field strength of 100 kG are in agreement with previous thin flux tube models in the absence of convection, whereas at low field strengths of 15 kG, the properties of the emerging loops are significantly changed. With convection, the rise times are drastically reduced, the loops are able to emerge at low latitudes, the majority of the emerging loops show tilt angles of the proper sign, and also show a field strength asymmetry consistent with the observed morphological asymmetry of active regions. We discuss the implications of these results with regard to the field strength of the dynamo generated large-scale toroidal magnetic field at the base of the solar convection zone. [Preview Abstract] |
Saturday, October 16, 2010 11:54AM - 12:06PM |
K1.00003: Photoevaporation of Cosmological Minihalos by the First Stars Thomas McConkie, Daniel Whalen, Robert Hueckstaedt Whalen et al. [1] conducted a survey which analyzed the effect of radiative feedback by one primordial star on subsequent star formation. Their study found results deviating from previous one-dimensional modeling. We extended the survey by performing two-dimensional simulations of cosmological minihalo evaporation using the astrophysical fluid hydrodynamic code ZEUS-MP. This code was run varying primordial star size (25 - 80 M$_{\odot})$, halo to star distance (150 - 1000 pc), and halo central density(1.43 - 1569 cm$^{-3})$. We find that the ionization front of the star penetrates nearby halos to varying degrees according to their central density and proximity to the star. The degree of penetration may prevent, postpone, delay or have no effect on star formation. \\[4pt] [1] D. Whalen, B. W. O'Shea, J. Smidt, and M. L. Norman, ``How the First Stars Regulated Local Star Formation. I. Radiative Feedback,'' The Astrophysical Journal 679, 925--941 (2008). [Preview Abstract] |
Saturday, October 16, 2010 12:06PM - 12:18PM |
K1.00004: Stellar Interferometry data analysis: a brute force approach to an inversion problem Ryan Price, Stephan LeBohec, Paul Nunez Stellar Interferometers provides measurements of the Fourier transform of the observed star image. With some techniques the phase information is lost and a direct inverse Fourier transform can not be used. However, it may be possible to evaluate the inverse Fourier transform of the data by using a more brute force method. The Fourier transform of an initial guess of the image is compared with the actual data by means of a chi2. The image is then optimized using a gradient method to minimize the chi2. Clearly this approach has severe limitations but seems to be usable as a post-processing technique for images obtained from more sophisticated phase recovery analyses. Advantages and disadvantages of this method are discussed and example applications are presented. [Preview Abstract] |
Saturday, October 16, 2010 12:18PM - 12:30PM |
K1.00005: Numerical Simulations of Planet Formation Benjamin Bromley, Scott Kenyon Planets in the Universe abound. In addition to the planets of the Solar System, we now know of hundreds of exosolar planets. In this talk we discuss our current understanding of how these planets form. Our focus will be on a hybrid code to simulate the process of planet formation from young protostellar disks of gas and dust to evolved systems with relatively few, fully-formed planets. We present results and predictions from this code and describe insights it provides into the nature of observed planetary systems. One important motivation for this research is that it may help determine if planets elsewhere in the Universe harbor life. [Preview Abstract] |
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