Bulletin of the American Physical Society
Joint Fall 2010 Meeting of the Texas Sections of the APS, AAPT, Zone 13 of SPS and the National Society of Hispanic Physicists
Volume 55, Number 11
Thursday–Saturday, October 21–23, 2010; San Antonio, Texas
Session FM2: Astrophysics, Astronomy, Space Science I |
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Chair: Daniel Boice, Southwest Research Institute Room: University Center III Bexar Room, 1st floor |
Friday, October 22, 2010 10:00AM - 10:12AM |
FM2.00001: HEMO -- The Hermean Exosphere Model of Oxygen: A Comprehensive Model for Interpreting Data from the MESSENGER and BepiColombo Missions to Mercury Emmanuel Grotheer A model, entitled Hermean Exosphere Model of Oxygen (HEMO) is presented. The main source processes that replenish the Hermean exosphere are ion sputtering, impact vaporization, photon stimulated desorption, and thermal desorption. Post-release, oxygen is affected by gravity, photoionization, photodissociation, and solar radiation acceleration. In addition, HEMO will incorporate a magnetosphere model to simulate ion trajectories both for sputtering and post-release. The sole in-situ data of oxygen, from Mariner 10, suggests a near-ground density of 4.4 E4 /cm$^3$. In this same paper, the sodium near-ground density is given as 1.7 -- 3.8 E4 /cm$^3$ [Shemansky, 1988]. The HEMO simulations aim to illuminate why oxygen detection is difficult, when it should be more abundant than sodium, since oxygen should account for 60{\%} of the Hermean crust [Killen et al., 2005]. The Hermean regolith is similar to the Lunar one, with some variations in species abundances. HEMO will run multiple times each for several representative sets of regoliths, Hermean orbital locations, and quiet and active Sun values. Results will be averaged to predict oxygen densities in Mercury's exosphere. The HEMO model results can aid in the interpretation of future oxygen data from the MESSENGER and BepiColombo missions to Mercury. [Preview Abstract] |
Friday, October 22, 2010 10:12AM - 10:24AM |
FM2.00002: Lyapunov Exponent Criterion in the CR3BP Billy Quarles, Jason Eberle, Manfred Cuntz, Zdzislaw Musielak Our specific focus is to describe the motion of an extra solar planet in a binary star system. We aim to accomplish this by using the methods of chaos theory as an alternate method to our previously established Hodograph method in the circular restricted 3-body problem (CR3BP). Previously Eberle et al. (2010) has shown that a parameter space exists depending only on the mass ratio $\mu $ and distance ratio $\rho _{o}$ which allowed them to identify regions of stability. Our method will validate the previous results while also providing more information relating to the presence of resonances and their effects on orbital stability. We extend the previous studies by increasing the simulation time, applying the method of Lyapunov exponents, calculating the time series spectrum of the orbit, and determining the Lyapunov dimension. The obtained results demonstrate when a system becomes unstable by orbital energy criterion and the method of Lyapunov exponents provides a quantitative classification scale to characterize the instability. By applying the maximum Lyapunov exponent (MLE) to the parameter space, we determine a region of stability with MLE values larger than the surrounding region. The time series spectra and the Lyapunov Dimension methods are used to illustrate the reasons behind the stability plateau which eludes to the resonance phenomena. [Preview Abstract] |
Friday, October 22, 2010 10:24AM - 10:36AM |
FM2.00003: Location, Structure, and Motion of Jupiter's Dusk Magnetospheric Boundary from $\sim $ 1625 to 2550 R$_{J}$ R.W. Ebert, D.J. McComas, F. Bagenal, H.A. Elliott We examine plasma observations along Jupiter's dusk magnetospheric flank from $\sim $1625 to 2550 R$_{J}$ using measurements from the SWAP instrument on New Horizons (NH). NH made sixteen magnetopause (MP) crossings that were identified by transitions between magnetotail/boundary layer and magnetosheath plasma. These transitions were either sharp, with the MP clearly separating two distinct plasmas, or comparatively gradual, where it was difficult to distinguish between different populations. The sheath distributions had high counts, were relatively wide in energy/charge (E/Q) and steadily decreased in speed. Flow speeds in the sheath were always higher (lower) when NH entered (exited) this region. A boundary layer was observed inside of the MP at several crossings. Its plasma was composed of light ions and the counts and mean E/Q were generally lower than sheath values indicating a lower density and speed. Estimates of angular displacement of the tail boundary compared favorably with a study of near Jupiter solar wind flow cone angle distributions. We propose that the outward crossings resulted from dawnward deflection and contraction of the tail from forward shocks/compression regions in the solar wind, the inward crossings from the duskward deflection and expansion of the tail from reverse shocks/rarefaction regions. [Preview Abstract] |
Friday, October 22, 2010 10:36AM - 10:48AM |
FM2.00004: The effect of sunspots cycle on satellite orbit M.A.K. Lodhi A satellite, traveling through the atmosphere, experiences a drag directly dependent on the atmospheric density. The fluctuation in the density thus affects the satellite's orbit. The effect of solar modulation, via Earth's atmospheric density, is experienced the satellite. A test case of a satellite orbit has been worked out to demonstrate this effect. The altitude of the satellite SSN 2909 for a period starting from 1970 to 2007 has gone down from 7290 km to 7170 km with a variation in the fall for certain periodic intervals. The satellite fall is much steeper for certain intervals and very gentle for the other intervals for about the same durations. The variations for those intervals correspond to the rate of change of altitude with respect to time for the same intervals. This shows that the fluctuations in the density do affect the satellite's orbit, which in turn are in exact agreement with fluctuations in the sunspots cycle. It is thus concluded that steep falls in the satellite's altitude occur when the sunspots activity is high and gentle changes occur during the low sunspots activity. [Preview Abstract] |
Friday, October 22, 2010 10:48AM - 11:00AM |
FM2.00005: Time-history of the isotopic ratios in Titan's atmosphere Kathleen Mandt, Hunter Waite, Jared Bell, Brian Magee Saturn's moon Titan is the only moon with a significant atmosphere, with a surface pressure of 1.5 times the surface pressure of Earth's atmosphere. The main constituents of Titan's atmosphere are molecular nitrogen (98{\%}) and methane (1.4{\%}). Diffusion, escape and chemical processes fractionate the isotopic ratios $^{14}$N/$^{15}$N in N$_{2}$, $^{12}$C/$^{13}$C in CH$_{4}$, and D/H in CH$_{4}$. Diffusion and escape result in a preferential loss of the lighter isotopes. Photochemistry may result in loss of the lighter isotopes in CH$_{4}$, but has been shown to have the opposite effect for N$_{2}$. A model constructed (Mandt et al. 2009) to track the isotopic ratios as a function of geologic time found that the $^{14}$N/$^{15}$N in N$_{2}$ could not have evolved from the terrestrial ratio to its current value as a result of atmospheric escape, and that the $^{12}$C/$^{13}$C measured in CH$_{4}$ limited the length of time for methane to have consistently resided in the atmosphere to less than 200 million years. Recent re-analysis of the Huygens GCMS data from Titan's surface (Niemann et al. 2010) has revised the $^{14}$N/$^{15}$N in N$_{2}$ and $^{12}$C/$^{13}$C in CH$_{4}$, resulting in significant changes to model results for the evolution of methane. We will present these updated results on the evolution of Titan's atmosphere and discuss the implications for the history of Titan. Mandt, K. E., et al., 2009, Planetary and Space Science, 57, 1917-1930. H.B.Niemann, et al., 2010. J. Geophys. Res., in press [Preview Abstract] |
Friday, October 22, 2010 11:00AM - 11:12AM |
FM2.00006: Further Measurements of the New Dwarf Nova J2138+26 Jared Rovny, Kyle Mezier, Irina Voloshina, Richard Olenick, Vladimir Metlov J2138+26 is a new WZ Sge-type dwarf nova, discovered by Dae-Am Yi et al. on May 7, 2010 (CBET 2273). The object is suggested to be similar to GW Lib, another WZ Sge star outbursting in 2007, in terms of a low inclination angle and apparent brightness. J2138+26 is a binary star system with a variable light output caused by precession of the accretion disk around the white dwarf in the cataclysmic variable system. J2138 enters certain periods of outburst when it is significantly brighter, and its regular light variations (from precession), called superhumps, have a changing period. Additional photometric observation of this system provides information about the changing amplitude and period of its superhumps and outbursts, which in turn helps to determine the system's history and physical activity, as well as providing insight into cataclysmic variable systems and their behavior in general. The research in July 2010, done by the named authors and using a 0.6-m telescope from the Sternberg Astronomical Institute's branch of the Crimean Observatory in Crimea, was focused on such photometric observation. Data and analysis of the superhump periods will be presented. The analysis of data taken by Dr. Voloshina and ourselves will be presented with a focus on the changing amplitude and period of J2138, and the physical significance of these results discussed. [Preview Abstract] |
Friday, October 22, 2010 11:12AM - 11:24AM |
FM2.00007: Density correlations between solar wind and pick-up ions with New Horizons/SWAP near 11 AU Brent Randol, David McComas The Solar Wind Around Pluto (SWAP) instrument aboard the New Horizons spacecraft measured ion energy spectra of the solar wind and pick-up ions between 11 and 12 AU in late 2008. We report on detailed fitting of these spectra using an empirical model that includes major solar wind ions (H+, He2+, and O6+) as well as pick-up ions (from the interstellar and inner sources). We find a correlation between the densities of the solar wind H+ ions and all other populations. The two strongest correlations are with the interstellar pick-up ions and the inner source pick-up ions. These results could have implications for transport of pick-up ions through the heliosphere. [Preview Abstract] |
Friday, October 22, 2010 11:24AM - 11:36AM |
FM2.00008: Observation and Analysis of J1625 +1203 Kyle Meziere, Richard Olenick, Irina Voloshina, Vladmir Metlov, Jared Rovny We observed and classified the object, J1625 +1203, in July 2010, which was discovered by the Catalina Real Time Sky Survey. Observations of this cataclysmic variable star were made over a two week period using the 60 cm telescope at the Sternberg Institute Crimean Observatory in Nauchny, Ukraine. A total of eight nights of professional grade data was collected, which was then processed and analyzed. The light curves obtained are characteristic of a Su UMa type dwarf novae undergoing a super hump outbursts. The super hump and orbital periods were calculated from the data and they further support the classification of J1625 as an SU UMa type dwarf nova. Data and characteristics of this object will be presented. [Preview Abstract] |
Friday, October 22, 2010 11:36AM - 11:48AM |
FM2.00009: Interstellar Boundary Explorer (IBEX) Observations of the Outer Heliosphere David McComas Global images of the heliosphere's interaction with the local interstellar medium have recently been published using observations from the Interstellar Boundary Explorer (IBEX) mission [McComas et al., \textit{Science}, 326, 5955, 2009 and related articles in the same issue]. IBEX observes energetic neutral atoms (ENAs) over the energy range from $\sim $100 eV -- 6 keV, emanating in from the interaction region at the edge of the heliosphere. In IBEX's first sky maps, we discovered a narrow, bright ribbon of ENA emissions unpredicted by any prior models or theories that appears to be ordered by the interaction of the heliosphere with the local interstellar magnetic field. This ribbon is superposed on more slowly spatially varying globally distributed ENA flux, which is ordered by both the solar wind structure and the direction of motion through the interstellar medium. IBEX observations indicate that the external galactic environment strongly imprints the heliosphere. This talk summarizes the published IBEX observations, examines the possibility that the ribbon structure may be evolving over the six months between IBEX's first and second sky maps, and discusses some of the possible ideas for what may be missing in our current understanding of the heliosphere's global interaction and creating this remarkable ribbon structure. [Preview Abstract] |
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