Other
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmsm33a..01l&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #SM33A-01
Other
2736 Magnetosphere/Ionosphere Interactions (2431), 2753 Numerical Modeling, 7827 Kinetic And Mhd Theory, 7833 Mathematical And Numerical Techniques (0500, 3200)
Scientific paper
We discuss the underpinnings of a multiple fluid approach to MHD simulation. By considering the effects of the inertial and diamagnetic drifts of different species, we can derive the multi-fluid MHD equations. As expected, the magnetic field constrains all of the species to have the same perpendicular velocity, while the parallel velocity of each component can be different. The two directions are not exactly independent; changes in the magnetic field direction affect the distribution of kinetic energy and momentum among the species. The familiar single fluid, ideal MHD equations have a number of robust conserved quantities: mass, momentum, energy, and the solenoidal nature of the magnetic field. These quantities are preserved even in the presence of dissipation, whether numerical or explicit, and allow the crafting of numerical schemes which automatically handle discontinuities such as shocks. There are other quantities, such as specific entropy and magnetic helicity, which are conserved in the absence of dissipation. Building numerical simulations based upon non-conserved variables requires carefully considering how dissipation, both numerical and explicit, enters into the scheme so as to conserve, at least approximately, what needs to be conserved. For a multi-component plasma, only the total (summed) momentum, and energy are conserved. Energy and momentum are transferred among the species by the action of the Lorentz force. The task, then, in developing a multi-fluid MHD code is similar to developing a single-fluid code based on non-conserved variables: dissipation must be carefully considered. For a single fluid code involving shocks, we have relatively more insight into what the solution should be. For example, in a shock in a multi-component plasma, are all the species heated, or can some be accelerated laminarly, giving their kinetic energy to others? Without specific knowledge of the kinetic, sub-grid-scale processes involved, we must make some ad hoc assumptions. We will discuss these assumptions, and the realm of applicability of the resulting equations tied into two specific examples: shocks where the two species have very different sonic Mach numbers and heating of plasma sheet ions in the numerical code.
No associations
LandOfFree
Multi-fluid MHD Simulations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Multi-fluid MHD Simulations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-fluid MHD Simulations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1400903