Physics @ Berkeley
Events in Physics
Title: 290B Space Physics Seminar    (Seminar)
Start Date: 03/21/2006
Time: 1:45 pm
Location: 508-20 Evans
Speaker: Yannis Zouganelis
Affiliation: UCB / Space Sciences Laboratory
Contact Person: Sam Lam   (510) 642-7297

Acceleration of the fast solar wind: a simple kinetic model
Yannis Zouganelis, UC Berkeley / Space Sciences Laboratory

It has been more than four decades since the existence of the solar wind has been confirmed by the measurements of the Mariner 2 spacecraft. However, the solar wind's acceleration at supersonic speeds of about 700-800 km/s still remains unexplained. Parker's theory, based on thermal conduction, results into a very low speed; this led most of the scientists to look for an additional form of energy in order to explain this acceleration.

The theoretical difficulty lies in the fact that the plasma is weakly collisional, a field of plasma physics that is still not well understood. The hydrodynamic models are based on local thermodynamic equilibrium, which is far from being true in the case of solar wind electrons. Indeed, the velocity distribution functions of the electrons measured in situ are not Maxwellian, but present an excess of suprathermal electrons.

In this seminar, we will discuss an alternative theory based on the role of electrons that are far from thermodynamic equilibrium and could be on the origin of the acceleration. This approach could explain the fast solar wind without any additional assumption on the energy.