Electric and magnetic contributions to spatial diffusion in collisionless plasmas
ADS link, DOI
Smets, R., Belmont, G., Aunai, N.
We investigate the role played by the different self-consistent fluctuations for particle diffusion in a magnetized plasma. We focus especially on the contribution of the electric fluctuations and how it combines with the (already investigated) magnetic fluctuations and with the velocity fluctuations. For that issue, we compute with a hybrid code the value of the diffusion coefficient perpendicular to the mean magnetic field and its dependence on the particle velocity. This study is restricted to small to intermediate level of electromagnetic fluctuations and focuses on particle velocities on the order of few times the Alfvén speed. We briefly discuss the consequences for cosmic ray modulation and for the penetration of thermal solar wind particles in the Earth magnetosphere.
Energy budgets in collisionless magnetic reconnection: Ion heating and bulk acceleration (ADS Link, DOI)
Aunai, N.; Belmont, G.; Smets, R.
This paper investigates the energy transfer in the process of collisionless antiparallel magnetic reconnection. Using two-dimensional hybrid simulations, we measure the increase of the bulk and thermal kinetic energies and compare it to the loss of magnetic energy through a contour surrounding the ion decoupling region. It is shown, for both symmetric and asymmetric configurations, that the loss of magnetic energy is not equally partitioned between heating and acceleration. The heating is found to be dominant and the partition ratio depends on the asymptotic parameters, and future investigations will be needed to understand this dependence.
I had my PhD defense on Feb. 11 2011 in Ecole Polytechnique, Palaiseau, France. The topic is “Numerical simulation of magnetic reconnection : kinetic mechanisms behind the fluid description”. (Link)