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Ann. Geophys., 25, 575-580, 2007
www.ann-geophys.net/25/575/2007/
© European Geosciences Union 2007
Unexpected sites of efficient stochastic acceleration in the inner heliosheath
S. V. Chalov1, H. J. Fahr2, and Y. G. Malama1,3
1Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow, Russia
2Argelander Institut für Astronomie, Abt.: Astrophysik, Universität Bonn, Bonn, Germany
3Space Research Institute (IKI), Russian Academy of Sciences, Moscow, Russia
Abstract. Up until the recent past, it was generally believed that the solar
wind termination shock (TS) is the favourite site to accelerate
ions from the keV- to the MeV- energy levels by means of Fermi-1
processes. When Voyager 1 was crossing the TS at the end of 2004,
the registrations of this spacecraft showed, however, that beyond
the shock passage fluxes of anomalous cosmic rays kept increasing
with time. This obviously called for an acceleration site further
downstream of the shock in the heliosheath which had not been
identified before. In this paper we thus investigate the process
of energy diffusion due to wave-particle interactions (Fermi-2)
operating on pick-up ions which are convected downstream of the TS
with the subsonic solar wind. We investigate the continuous effect
of stochastic acceleration processes suffered by pick-up ions at
their interaction with heliosheath turbulences, while they are
slowly convected with the subsonic solar wind towards the
heliotail. As we can show, the inner heliosheath region, with an
extent of about 100 AU around the solar wind stagnation point, is
specifically favourable for the energy processing of pick-up ions
by Fermi-2 processes up to MeV energies. In addition, we claim that
this region is the origin of multiply-charged anomalous cosmic ray
particles that have been registered in recent times.
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