Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session M15: Space and Astrophysical Plasma |
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Sponsoring Units: DPP Chair: Michael Brown, Swarthmore College Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis H |
Sunday, April 13, 2008 3:30PM - 3:42PM |
M15.00001: Gravity Damping in Neutron Star Magnetospheres Steven Bekhor It was shown previously by Khabibrakhmanov and Mullan that a mechanism whereby Alfv\'{e}n waves dissipate energy in gravitationally structured media via Joule heating may account for solar coronal heating and wind driving. In particular, ``gravity damping'' was shown to preferentially heat heavy ions and produce temperature anisotropies (T$_{\bot } >$ T$_{\vert \vert })$, features that have long been known to exist in the solar wind and low corona. We present the results of preliminary asymptotic and numerical studies that extend this phenomenon to general relativistic regimes. In particular, the dynamics of ubiquitous, virtually undamped gravitational waves that radiate from neutron stars are examined using a multi-fluid description of the outer magnetosphere medium in the Newtonian limit of General Relativity as well as in the 3+1 split formalism. It is thought that gravitational waves are driven by oscillations within the superfluid interior and, therefore, may provide a very important source of energy for magnetospheric acceleration processes. Future results will ultimately be compared to realistic spectra from LIGO and VIRGO. [Preview Abstract] |
Sunday, April 13, 2008 3:42PM - 3:54PM |
M15.00002: The influence of radiation on shocks structure in laboratory astrophysics Matthias Gonzalez, Edouard Audit, Chantal Stehle, Michel Busquet Radiative shocks are found in various astrophysical situations such as stellar accretion. Studying such shocks, their topology and thermodynamical properties is the starting point to understand their physical properties. This study is now possible with the recent development of large laser facilities which has therefore given a strong impulse to laboratory astrophysics. We present the main characteristics of radiative shocks obtained in such installations thanks to results obtained in experiments and with our multi-dimensional radiation-hydrodynamics code HERACLES. We focus our discussion on the importance of multi-dimensional radiative transfer effects on the shock topology and dynamics. In particular, the importance of the ratio between the photon mean free path and the transverse extension of the shock, the possibility to achieve the stationary limit in the laboratory and the angular distribution of the radiative flux which emerge at the walls of the tube are discussed. [Preview Abstract] |
Sunday, April 13, 2008 3:54PM - 4:06PM |
M15.00003: Production of Magnetic Turbulence by Cosmic Rays Drifting Upstream of Supernova Remnant Shocks Martin Pohl, Jacek Niemiec, Tom Stroman We present results of 3-D Particle-In-Cell simulations of magnetic turbulence production by cosmic-rays drifting upstream of supernova remnant shocks. The studies aim at testing the predictions of a strong amplification of short-wavelength nonresonant wave modes and at studying the subsequent evolution of the magnetic turbulence and its backreaction on cosmic ray trajectories. We confirm the generation of the turbulent magnetic field due to the drift of cosmic-ray ions in the upstream plasma, but show that an oblique filamentary mode grows more rapidly than the nonresonant parallel modes found in analytical theory. The growth rate of the field perturbations is slower than estimated for nonresonant modes using the quasilinear approach, and the amplitude of the turbulence saturates at about $\delta B/B\sim 1$. [Preview Abstract] |
Sunday, April 13, 2008 4:06PM - 4:18PM |
M15.00004: ABSTRACT WITHDRAWN |
Sunday, April 13, 2008 4:18PM - 4:30PM |
M15.00005: Relativistic MHD Jets and Their Interactions with the Intra-cluster Medium: Plasma Physics at its Extreme Hui Li, Masanori Nakamura, Shengtai Li, Hao Xu We present the formulation of magnetically dominated relativistic MHD flows as a model for extra-galactic jets produced by accretion onto supermassive black holes. Three-dimensional relativistic MHD simulations will be presented on how the energy outflow partitions among different physical components and on how the collimation occurs. We will also examine the stability of such systems. Similar to many of the laboratory plasma systems, current driven instabilities are crucial to jet dynamics, though relativistic velocities and expanding boundaries can significantly change the stability properties. In addition, the interaction between such flows with their environment, e.g., the intra-cluster medium, will be studied. 3-D instabilties that lead to flux conversion seem to be necessary for both the jet stability and the radio lobe formation. Simulations are compared with observations of X-ray cavities in clusters and the possibility of lobes being magnetically dominated on global scales will be discussed. We incorporate such models as AGNs in large scale cosmological cluster formation simulations to study the AGN feedbacks on structure formation. The morphology and properties of jet-lobe systems in realistic cluster simulations will be presented. [Preview Abstract] |
Sunday, April 13, 2008 4:30PM - 4:42PM |
M15.00006: X-ray emission from charge-exchange: An astrophysical plasma diagnostic tool. Thomas Cravens, Ina Robertson, Steven Snowden, Michael Collier, Kip Kuntz, Mikhail Medvedev, Kenneth Hansen Astrophysical x-rays typically come from hot collisional plasmas, such as the solar corona or supernova remnants. However, x-rays can also be produced in cooler gas by charge exchange (CX) collisions between neutrals and highly-charged ions. The CX mechanism applied to the solar wind has been shown to generate x-ray emission at comets, in the terrestrial magnetosheath, and throughout the heliosphere (where the solar wind interacts with incoming interstellar neutral gas). Heliospheric emission is thought to make a significant contribution to the observed soft x-ray background (SXRB). Efforts are underway to distinguish this contribution from emission due to hot interstellar gas and the galactic halo. X-rays from CX could provide diagnostic information (e.g., line ratios) on regions where hot astrophysical plasma comes into contact with neutral gas. [Preview Abstract] |
Sunday, April 13, 2008 4:42PM - 4:54PM |
M15.00007: Effects of Electron Self-Force on Superstrong Laser Pulse Natalia M. Naumova, Igor V. Sokolov, Victor P. Yanovsky, John A. Nees, Gerard A. Mourou We analyze the effect of self-force on a single electron and on plasma electrons giving attention to the electromagnetic energy generated by an accelerated motion in a field of a relativistically strong electromagnetic wave. The effect is essential if the scattered energy is comparable with the rest-mass energy of the electron in the frame of reference where the electron was initially at rest. We develop a method for solving the Lorentz-Abraham-Dirac equation and accounting for radiation in a self-consistent manner. The solution is then applied to the interactions of super-strong laser fields with an electron and a plasma layer including the presence of strong charge separation fields. This scheme allows a simulation of resulting radiation with spatial and spectral distributions. We consider a conversion efficiency of incident radiation to $\gamma $-ray emission at intensities of 10$^{22}$ - 10$^{24}$ W/cm$^{2}$. [Preview Abstract] |
Sunday, April 13, 2008 4:54PM - 5:06PM |
M15.00008: A Self-Consistent Description of Dust Interactions in Space and Nano-structured Plasmas Steven Bekhor The effect of nano/micro-structures and dust voids on the dispersion relations and the overall dynamics of plasma waves has numerous applications in the study of laboratory and space plasmas such as planetary rings and lunar and asteroidal dust. In particular, elastic Coulomb collisions with dust particles and charging interactions affect the overall particle balance of the plasma species and must be investigated self-consistently. Furthermore, in the low-frequency limit, a comprehensive theory must account for the dynamics of both electrons as well as ions, especially in strongly collisional regimes where the use of the full Braginski equations is warranted. In the current treatment, the fluid equations are developed to address a large class of problems involving space plasmas and nanofabrication. It so happens that dust charging results in a new channel of power dissipation that may explain numerous phenomena in such complex self-organized thermodynamically open systems. Numerous examples are presented and the stage is set for future numerical efforts. [Preview Abstract] |
Sunday, April 13, 2008 5:06PM - 5:18PM |
M15.00009: ABSTRACT WITHDRAWN |
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