Part I. Talks

Section D. Particle Acceleration in Astrophysical Plasmas



Title: Particle Acceleration in Solar Flares
Author: J. A. Miller
Affil: Department of Physics, The University of Alabama in Huntsville, Huntsville, AL 35899, U.S.A.
Abstract: We review the basic, observationally driven requirements for a successful model of particle acceleration in impulsive solar flares and then evaluate the viability of three classes of acceleration mechanisms. We argue that stochastic resonant acceleration is by far the most promising of the mechanisms.


Title: Particle Acceleration at Astrophysical Shocks
Author: A. Achterberg
Affil: Sterrenkundig Instituut, Postbus 80000, 3508 TA Utrecht, The Netherlands
Abstract: The acceleration of particles in the vicinity of astrophysical shocks has become the main paradigm in astrophysics for the production of superthermal and relativistic particles. In this review, I consider the basic theory of shock acceleration and the open questions.


Title: Ultrahigh Energy Cosmic-ray Accelerators
Author: A. V. Olinto
Affil: Department of Astronomy & Astrophysics & Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, U.S.A.
Abstract: The surprising lack of a high energy cutoff in the cosmic ray spectrum at the highest energies, together with an apparently isotropic distribution of arrival directions, have strongly challenged most models proposed for the acceleration of ultrahigh energy cosmic rays. Young neutron star winds may be able to explain the mystery. We discuss this recent proposal after summarizing the observational challenge and plausible acceleration sites. Young neutrons star winds differ from alternative models in the predictions for composition, spectrum, and angular distribution, which will be tested in future experiments.


Title: Electron Acceleration by Strong DC Electric Fields in Extragalactic Jets
Author: Y. E. Litvinenko
Affil: Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824-3525, U.S.A.
Abstract: Fast magnetic reconnection in extragalactic jets leads to electron acceleration by the DC electric field in the reconnecting current sheet. The maximum electron energy (gamma > 10^6) and the acceleration time (< 10^6 s) are determined by the magnetic field dynamics in the sheet.


Title: Radio Evidence for Nonthermal Particle Acceleration in Normal Stars
Author: K. R. Lang
Affil: Department of Physics and Astronomy, Tufts University, Medford, MA 02155, U.S.A.
Abstract: The Very Large Array has been used to detect nonthermal radio emission from nearby stars of late spectral type F, G, K, and M, and has provided unique high-resolution investigations of the Sun's radio emission.


Title: Wave-powered Relativistic Electron Generation in Nonuniform Magnetic Fields
Author: M. P. Leubner
Affil: Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
Abstract: The generation of superthermal electron populations due to resonant energy transfer from Alfven wave packets can be studied sufficiently well within the Fokker-Planck diffusive formalism, where the particle energization is induced through Landau interaction. From the calculation of the magnetic-field--dependent diffusion operator of an Alfven wave spectrum, it is demonstrated how resonant energization can be forced in nonuniform magnetic field configurations. On this basis, a mechanism for the acceleration of electrons from thermal to relativistic energies is presented where the specific magnetic field geometry acts as catalyst, providing a highly effective source for synergetic electron energization.