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 H5: Astrophysicists' Perspectives on Current Problems in Plasma Astrophysics II |
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Sponsoring Units: GPAP DAP Chair: Dmitri Uzdensky, Princeton University Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade C |
Sunday, April 13, 2008 8:30AM - 9:06AM |
H5.00001: Pulsars, Magnetars, and Jets-Problems and Lessons for Astrophysical Plasma Physics Invited Speaker: Pulsars, magnetars and relativistic jets motivate investigations of plasma behavior well beyond the realms experimentally accessible in the laboratory or through in situ measurements in the heliosphere. Prominent among the areas of current research (the ``known unknowns'') are the role of relativistic shock waves in converting ultrarelativstic flow energy into nonthermal particle spectra observed. I discuss aspects of what we know about this problem, along with where such acceleration physics is appropriate - essentially, to weakly magnetized flows. I also discuss the still less well understood strongly magnetized regime (magnetic energy density exceeding plasma rest energy density in the flow proper frame), where phenomenological models suggest that some form of magnetic dissipation, quite possibly mediated by current sheet formation, underlies the observed emissions. Such dissipation also appears to play a role to the conversion of strongly magnetized flows into weakly magnetized, shock dominated systems, a special case of the relativistic magnetic dissipation problem which I will also address. [Preview Abstract] |
Sunday, April 13, 2008 9:06AM - 9:42AM |
H5.00002: Accretion Disks and Jets Around Black Holes Invited Speaker: Some of the most luminous objects in the universe involve accretion disks around black holes. In these systems, gas spirals into the black hole and converts a fraction of its gravitational binding energy into thermal energy and radiation. Sometimes, twin relativistic jets are ejected along the angular momentum axis of the disk. Understanding the physics of black hole accretion disks and jets is a major focus of modern astrophysics. Because the object at the center is a black hole, one must work with a relativistic theory. More importantly, one must allow for the effects of magnetic fields. These play an extremely important role, both in the extraction of angular momentum from the accreting gas -- which is what allows the gas to fall into the hole -- and in the launching, acceleration and collimation of the relativistic jets. Thus, at a minimum, one must work with the relativistic single-fluid MHD equations. The talk will briefly summarize our current understanding of black hole accretion, and outline some of the major unsolved problems. [Preview Abstract] |
Sunday, April 13, 2008 9:42AM - 10:18AM |
H5.00003: Some Things I Wished I Understood Better (or at all...) Invited Speaker: Astrophysics has, since its very beginnings, sought to build our understanding of astronomical phenomena on the solid foundation of our understanding of physical phenomena in the terrestrial context. In areas such as spectroscopy, this approach has had outstanding success; but in other areas, making this connection in an intellectually rigorous way has proved to be very challenging. I will discuss some of the most troublesome examples, and offer some guidelines on how the resulting uncertainties in our understanding of the astrophysical phenomena can be circumscribed. [Preview Abstract] |
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