scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Solar wind turbulence and production of proton beams
Voitenko Yuriy , Pierrard Viviane
Belgian Institute for Space Aeronomy
Super-Alfvénic proton beams are a common observation in the fast solar wind, but their origin
is still uncertain. We consider the possibility that these beams are generated by the dissipation
range of the solar wind turbulence. In accordance to modern turbulence theories, the spectral
energy transport in the solar wind is dominated by the perpendicular cascade towards small
perpendicular length scales. When the cross-field wavelengths become of the order of ten ion
gyroradii or less, kinetic effects come into play initiating wave-particle interactions and
plasma energization. In this case the dissipation range of the solar wind turbulence is formed
by highly oblique kinetic Alfvén waves (KAWs). We study the field-aligned electric potential
well created by the KAWs in the dissipation range and its effect on the solar wind protons.
The average KAW potential propagates with the super-Alfvén velocity that depends on the
KAW spectral index and spectral breaks in such a way that it is larger in the old (developed)
turbulence than in the young (under-developed) turbulence. We show that the protons trapped
by the potential well closer to the Sun, where the turbulence is younger, can be accelerated to
1.5-2 Alfvén velocities at larger heliocentric distances, where the turbulence is older, building
up the proton beam with the relative number density about 0.1.