Mathematics – Logic
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm13a1118b&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SM13A-1118
Mathematics
Logic
2744 Magnetotail, 2764 Plasma Sheet, 7827 Kinetic And Mhd Theory, 7833 Mathematical And Numerical Techniques (0500, 3200), 7835 Magnetic Reconnection (2723, 7526)
Scientific paper
During slow, quasi-static evolution in the collisionless magnetotail the entropy (S) as a function of magnetic flux (A) is a much better conserved quantity than the plasma pressure function P(A). The entropy profile S(A) has been found to be quasi-conserved even in scenarios involving topology change through magnetic reconnection, as long as the dissipation is very localized. Even though entropy conservation is a better constraint for space plasmas, most available plasma equilibrium solvers take the pressure profile P(A) as an input. This is mostly due to the difficulty of computing equilibria with S(A) input: as opposed to prescribing the current or pressure profiles for plasma equilibrium (which leads to the conventional Grad-Shafranov elliptic partial differential equation), prescribing the entropy results in a nonstandard differential equation whose solution by usual iterative techniques is not guaranteed. To solve this nonstandard equation we have developed a numerical code based on the 'alternating dimensions method' (ADM) suggested by Grad et al., [1975]; the code alternates between solving the 2D Grad-Shafranov equation to obtain the field configuration (flux function A) from the pressure profile P(A) and a 1D ordinary differential equation that uses the entropy profile to derive the pressure function P(A) from a flux surface average. We apply this method to 2 cases relevant to the magnetotail, both involving topological change in the transition from the initial to the final state: first, the code is applied to a forced magnetic reconnection problem (the 'Newton Challenge'), and the resulting equilibria obtained with various boundary deformations are compared with snapshots from dynamic MHD simulations. The second application starts from a more realistic magnetotail geometry that includes magnetic field line flaring. Assuming entropy conservation, we compute possible final equilibria with reconnected topology, and contrast them to equilibria obtained with unchanged P(A) profile. We also discuss how much magnetic energy is converted into thermal energy through topological change in both scenarios.
Birn Joachim
Zaharia Sorin G.
No associations
LandOfFree
Plasma Equilibrium With Entropy Input and Applications 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 Plasma Equilibrium With Entropy Input and Applications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasma Equilibrium With Entropy Input and Applications will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1421035