Hybrid Expanding Box Description of the Accelerating Solar Wind: Mirror Force Effects
Abstract
The expanding box model (Grappin et. al., PRL 1993) describes the effects of the spherical expansion of the solar wind on the thermodynamics, turbulence and kinetic properties of a plasma parcel moving outwards from the sun. It has been used to study, e.g., the evolution of Alfvén waves in MHD and the preferential heating of ions kinetically. If the average solar wind speed is constant, the expanding box equations can safely ignore higher order effects due to the mirror force which particles feel in the inhomogeneous large scale heliospheric magnetic field. However, in the acceleration region of the solar wind, such effects can be important. We include this higher order effect in the expanding box equations and study the evolution of particle distribution functions with expansion. The mirror force accelerates (along the mean field) particles with higher perpendicular thermal velocities and decelerates the ones with lower perpendicular thermal velocities, distorting the distribution function as the plasma accelerates outwards. Here we discuss the effects of this competition between the mirror force effects and expansion effects in the presence of multiple ion species.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSH53A2259P
- Keywords:
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- 7509 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Corona;
- 7863 SPACE PLASMA PHYSICS / Turbulence;
- 7899 SPACE PLASMA PHYSICS / General or miscellaneous