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Ann. Geophys., 23, 643-650, 2005
www.ann-geophys.net/23/643/2005/
© European Geosciences Union 2005
Reforming perpendicular shocks in the presence of pickup protons: initial ion acceleration
R. E. Lee1, S. C. Chapman1,2, and R. O. Dendy1,3
1Space and Astrophysics Group, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
2Radcliffe Institute for Advanced Study, Harvard University, USA
3UKAEA Culham Division, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK
Abstract. Acceleration processes associated with the heliospheric termination
shock may provide a source of anomalous cosmic rays (ACRs). Recent
kinetic simulations of supercritical, quasi-perpendicular shocks have
yielded time varying shock solutions that cyclically reform on the
spatio-temporal scales of the incoming protons. Whether a shock solution
is stationary or reforming depends upon the plasma parameters which, for
the termination shock, are ill defined but believed to be within the
time-dependent regime. Here we present results from high phase space
resolution
particle-in-cell simulations for a three-component plasma (solar
wind protons,
electrons and pickup protons) appropriate for the termination
shock.
We find reforming shock solutions which generate suprathermal
populations for both proton components, with the pickup ions reaching
energies of order twenty times the solar wind inflow energy. This suprathermal
"injection" population is required as a seed population for subsequent
acceleration at the shock which can in turn generate ACRs.
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