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 J6: Jets and Gamma Ray Bursts |
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Sponsoring Units: DPP GPAP Chair: Hui Li, Los Alamos National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade D |
Sunday, April 13, 2008 10:45AM - 11:21AM |
J6.00001: Magnetohydrodynamics of Gamma-Ray Burst Jets Invited Speaker: Magnetic fields are believed to play a dominant role in driving and collimating astrophysical jets, including the relativistic outflows that emanate from the vicinity of the supermassive black holes in active galactic nuclei and the ultrarelativistic jets, evidently associated with solar-mass black holes or rapidly rotating neutron stars, that are inferred to give rise to gamma-ray bursts (GRBs). Recent numerical simulations using special-relativistic, axisymmetric, ideal MHD have demonstrated the viability of this mechanism and revealed the detailed structure of relativistic plasma outflows of this type. The main results of these simulations are presented and analyzed, and their qualitative properties are explained with the help of steady-state, radially self-similar, semianalytic solutions and asymptotic analytic scalings. The distinctions between relativistic and nonrelativistic outflows and between MHD and purely hydrodynamic acceleration are highlighted, and the possible effect of initial thermal driving in GRB sources is discussed. Remaining open questions related to the general modeling of such outflows and to the specific application to GRB jets are pointed out. [Preview Abstract] |
Sunday, April 13, 2008 11:21AM - 11:57AM |
J6.00002: Jets in Relativistic Cosmic Explosions Invited Speaker: In this talk the speaker will first review relativistic cosmic explosions: gamma-ray bursts and radio sparks. GRBs are now recognized to be the most relativistic and highly collimated explosions. Radio sparks is an entirely new phenomenon (we have only one example as of November 2007). However, circumstantial evidence shows that this event is at extra-galactic distance. If so, these involve ultrra-strong electromagnetic waves. The plasma physics of GRB jets and radio sparks is a frontier area of astronomy with only questions! [Preview Abstract] |
Sunday, April 13, 2008 11:57AM - 12:33PM |
J6.00003: Prize to a Faculty Member for Research in an Undergraduate Institution Talk: Bidirectional outflow jets in the SSX reconnection experiment Invited Speaker: Several new experimental results are reported from plasma merging studies at the Swarthmore Spheromak Experiment (SSX) with relevance to collisionless three dimensional magnetic reconnection in laboratory and space plasmas. First, recent high-resolution velocity measurements of impurity ions using ion Doppler spectroscopy (IDS) show bi-directional outflow jets at $40~km/s$ (nearly the Alfv\'en speed). Second, ion heating to nearly $10^6~K$ is observed after reconnection events in a low density kinetic regime. 3D particle simulations reveal a population of trapped ions heated by the outflow. Transient electron heating is inferred from bursts on a 4- channel soft x-ray array. Third, the out-of-plane magnetic field in a reconnection volume shows a quadrupolar structure at the ion inertial scale. Time resolved vector magnetic field measurements on a 3D lattice (${\bf B}(r,t)$) enables this measurement. Each of these measurements will be related to and compared with similar observations in a solar or space context. [Preview Abstract] |
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