Bulletin of the American Physical Society
Fall 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students
Volume 60, Number 15
Thursday–Saturday, October 29–31, 2015; Waco, Texas
Session N3: Astronomy, Astrophysics and Space Science II |
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Chair: William Newton, Texas A&M University Room: C.206 |
Saturday, October 31, 2015 10:30AM - 10:42AM |
N3.00001: Using machine learning to interpret ground-level PM2.5 distribution in east Asia in 2004-2013 Daji Wu Airborne particulate matter has substantial health and climatic impacts. In this study we use machine learning to aid the analysis of a comprehensive global particulate dataset. Our focus is on an average annual cycle at a 10 km spatial resolution and a 10-day temporal resolution covering the period 2004-2013 (i.e. each grid point has an annual cycle described by thirty-six 10 day averages). We then use an unsupervised classification (self-organizing map) to objectively characterize the shape of the annual cycles into 100 classes. Locations in a given class have annual cycles of a very similar shape. The different classes are depicted geographically using different colors on a map. The self-organizing map is able to clearly separate urban and rural areas in Sichuan, China. In order to find the precise relationship between the shapes of these annual cycles with the meteorological context, we use random forests to rank the top 20 most important variables in determining the shape of the PM$_{2.5}$ annual cycle. The machine learning is a useful assistant in giving the data a voice. [Preview Abstract] |
Saturday, October 31, 2015 10:42AM - 10:54AM |
N3.00002: High HOPEs: Modeling Electric Fields in Earth's Plasmasphere to Estimate Its Temperature Grace Corley, Will Farner, Kevin Genestreti, Jerry Goldstein, Brian Larsen, Chae Ramnarace, Geoff Reeves, Ruth Skoug, Harlan Spence, Niescja Turner The plasmasphere is a region of cold, dense plasma in the Earth's inner magnetosphere and outer ionosphere. The plasma is composed of three major ion species (hydrogen, oxygen, helium), and electrons. Onboard each of the two Van Allen probes spacecraft (which pass through the plasmasphere once per orbit), the HOPE (Hydrogen Oxygen Protons Electrons) instruments count the number of particles, per position per velocity, for each ion species. These HOPE data can be fitted to an equilibrium distribution function to describe the particles in the plasmasphere. Because of the electric fields produced by when the Van Allen spacecraft perturb the ambient plasma, HOPE can only measure the high-energy tail of the plasmasphere. In order to fit the distribution function to calculate the temperature from these limited data, we constrain the open parameters, bulk velocity and density. The motion of the plasmasphere is subject to ExB drift from Earth's geomagnetic and electric fields. In this project, we model corotation and convection electric fields using solar wind data to constrain the bulk velocity of the plasmasphere. [Preview Abstract] |
Saturday, October 31, 2015 10:54AM - 11:06AM |
N3.00003: Variable Star Search Using ROTSE-I Data Daniel Gum, Farley Ferrante, Robert Kehoe I present the results of a variable star search using data from the Robotic Optical Transient Search Experiment--I (ROTSE-I) telescope.~Variable stars fluctuate in magnitude as seen from Earth due either to changes in the star's luminosity or to changes in the amount of the star's light that reaches the Earth. My research focused on analysis of the time variation of optical light output as recorded in the ROTSE--I data sets. The data contained output from several types of variable stars, all of which are short period variables such as Delta Scuti stars, eclipsing binaries, and contact binaries. Amplitude variations for these classes of variables are on the order of one magnitude with periods on the order of 2 to 15 hours. These stars are relatively bright, with brightness values ranging between the 11$^{\mathrm{th}}$~and 14$^{\mathrm{th\thinspace }}$magnitudes. As such, they were ideal candidates for observation from the ROTSE-I telescope. The variable star discoveries are now listed in the International Variable Star Index (VSX) maintained by the American Association of Variable Star Observers (AAVSO). [Preview Abstract] |
Saturday, October 31, 2015 11:06AM - 11:18AM |
N3.00004: Modeling the fluid dynamics of a protoplanetary disk in a tabletop experiment Ruy Ibanez, Bruce Rodenborn, Harry Swinney In 2001 Molemaker et al. (\textit{J. Fluid. Mech.} {\bf 448}, 1) predicted a new class of instabilities in a system of concentric rotating cylinders that contains a fluid with a vertically varying density. Dubrulle et al. (\textit{Astron. Astrophys}. {\bf 429}, 1, 2005) then showed that this phenomenon, which they named stratorotational instability (SRI), could be a source of instability and angular momentum transport in astrophysical accretion disks. Such a flow has strong Coriolis forces, velocity shear and a vertical density gradient, which are properties shared by protoplanetary accretion disks. Our understanding of these processes in a laboratory system may lend insights into the means by which angular momentum is transported radially outward in accretion disks. Our observations suggest that current theory breaks down for high rotation rates and strong density gradients. Instead, we observe a new state that may show the onset of turbulence. We also study the temporal and spatial characteristics of the SRI, which generates a spiral pattern. We find that the spatial wavelength depends on the rotation rate and density variation, while the temporal frequencies are approximately multiples of the average rotation frequency of the inner and outer cylinder. [Preview Abstract] |
Saturday, October 31, 2015 11:18AM - 11:30AM |
N3.00005: Investigating cosmological parameters using \texttt{CosmoEJS}, an interactive package of cosmology Java simulations Jacob Moldenhauer, Francis Cavanna, William O'toole, William Zimmerman There is a recent influx of cosmological observations which appear to suggest that the universe's expansion is accelerating. Several theories offer an explanation for this observed phenomenon. It is important to know the impact of changing certain cosmological parameters of a particular model has on matching a particular data set. \texttt{CosmoEJS} is an interactive \texttt{Java} package of simulations that allow the user to explore the ramifications of choosing various values for the cosmological parameters of a particular model. The simulations include different classes of models and observations of both expansion and growth history of the universe. After exploring the fitting of different models, the user can then see these models evolve in time. [Preview Abstract] |
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