Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session Q3: Particle Acceleration |
Hide Abstracts |
Sponsoring Units: DAP DPP Chair: James Drake, University of Maryland Room: Hyatt Regency Dallas Landmark C |
Monday, April 24, 2006 1:30PM - 2:06PM |
Q3.00001: Observing Particle Acceleration with RHESSI Invited Speaker: The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) was designed to study particle acceleration in solar flares by imaging spectroscopy of both bremsstrahlung from electrons and nuclear lines from ion interactions. I will review several of the major results of these studies since the launch of RHESSI in February 2002. RHESSI's x-ray and gamma-ray detectors are also being used to study electrons accelerated to high energies in other sites, such as the Crab nebula and thunderclouds on Earth; I will review the status of these observations as well. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q3.00002: Current Status of Shock Acceleration Theory Invited Speaker: The main features of nonlinear diffusive shock acceleration are now reasonably well understood after several decades of work by many individuals. Several distinct approaches have converged to give a reasonably consistent picture of the process. These will be briefly described. The interesting new development in the last few years is the increasing attention being paid to mesoscopic instabilities and their potential importance for magnetic field amplification, This may well be the last missing piece of the jig-saw, but raises serious technical problems for the theoretical study of the acceleration process as well as some fascinating physics issues. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q3.00003: The Importance of magnetic-field angle in diffusive shock acceleration of cosmic rays Invited Speaker: We discuss the physics of charged-particle acceleration by shock waves, focussing on the importance of the shock-normal angle. This has important applications for our understanding of supernovae shocks, the solar-wind termination shock, and propagating shocks near the Sun. For the case in which the shock normal is parallel to the incident field - a parallel shock - acceleration of particles to very high energies (e.g. the knee in the cosmic-ray spectrum, or $>$GeV energy solar cosmic rays) requires very special conditions to explain the observations. These include a strong increase in the magnetic field, perhaps due to excitation from the streaming cosmic rays. In this talk, we show that no such special circumstances are required when one considers acceleration at nearly perpendicular shocks. We suggest that the observations of high-energy charged particles can be accounted for using reasonable values for the diffusion coefficients and observed shock speeds. A critical issue in the theory of diffusive shock acceleration at nearly perpendicular shocks is the well-known injection problem. We suggest that, in actuality, there is no such injection problem and, in fact, the acceleration efficiency does not depend strongly on the shock-normal angle. This can be understood in terms of the increased cross-field transport arising from so-called field-line random walk due to the large-scale (ccompared to the particle gyroradii) turbulent magnetic field. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700