HR: 0800h
AN: SH31A-1152    [Abstracts]
TI: Acceleration of the Weakly Collisional Solar Wind
AU: * Zouganelis, I
EM: ioannis.zouganelis@obspm.fr
AF: LESIA-Observatoire de Paris, 5, Place Jules Janssen, Meudon, 92195 France
AU: Meyer-Vernet, N
EM: nicole.meyer@obspm.fr
AF: LESIA-Observatoire de Paris, 5, Place Jules Janssen, Meudon, 92195 France
AU: Landi, S
EM: slandi@arcetri.astro.it
AF: Dipartimento di Astronomia e Scienza dello Spazio, Largo Enrico Fermi 2, Florence, 50125 Italy
AU: Maksimovic, M
EM: milan.maksimovic@obspm.fr
AF: LESIA-Observatoire de Paris, 5, Place Jules Janssen, Meudon, 92195 France
AU: Pantellini, F
EM: filippo.pantellini@obspm.fr
AF: LESIA-Observatoire de Paris, 5, Place Jules Janssen, Meudon, 92195 France
AB: A major assumption inherent to the usual fluid solar wind models is that the plasma is dominated by collisions. Therefore the fluid approach implies that the particle velocity distribution functions are close to Maxwellians. However the observed solar wind electron distributions depart significantly from Maxwellians, indicating the limited validity of this hypothesis. Collisionless models are not fully justified either, but should bring some insights into the physics since heat transport is mainly driven by suprathermal particles which are virtually collisionless because of the rapid increase with energy of the Coulomb free path. A proper theory should take into account the transition from a fully collisional regime to a weakly collisional one. If we neglect interactions with waves, the existence of a transonic plasma wind depends mainly on the electrostatic field and the heat flux which are determined by the velocity distributions of particles. In this work we present recent developments of a kinetic collisionless model of the solar wind and compare them with results obtained by numerical simulations that include collisions. Two important results emerge: a suprathermal tail in the electron velocity ditribution function enables to explain the fast wind and both models give the same speeds over a large range of parameters.
DE: 7509 Corona
DE: 7800 SPACE PLASMA PHYSICS
DE: 7827 Kinetic and MHD theory
DE: 7843 Numerical simulation studies
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting