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.