Phasespace structures in plasma turbulence
Here is a glimpse of my current research. This is a kinetic simulation of electrostatic waves in a bumpontail plasma, with multiple resonances and some dissipation. Quasilinear theory predicts a flattening of the velocity distribution over the range of resonant velocities of linearly unstable modes. However, selfcoherent phasespaces structures known as holes and clumps change this picture significantly.
This physics is relevant to tokamaks (magnetically confined fusion devices), where the frequencies of several coexisting Alfvén eigenmodes, which are driven by energetic ions, have been observed to sweep in time (chirping). Chirping is a signature of evolving holes and clumps. What I am wondering is whether there are implications in space plasma. Do you know of any experimental observation or theoretical work on the nonlinear effect of phasespace structures on turbulence? More on this simulation: Nonlinear growth, evolution and interaction of selfcoherent phasespace structures in a dissipative bumpontail plasma simulation with multiple resonances, using the kinetic code COBBLES. Up: perturbed distribution function. Down: spatiallyaveraged velocity distribution. Dashed vertical lines at the beginning of the video show the resonances that are linearly unstable. Holes are in blue and clumps are in yellow. Quasilinear theory predicts a flattening of the velocity distribution over the range of resonant velocities of linearly unstable modes. However, selfcoherent phasespaces structures known as holes and clumps change this picture significantly. During this simulation, several hole/clump pairs spontaneously emerge at different resonance velocities and subsequently merge with each others, until there remains mainly one single hole. Note that phasespace structures survive for a collisional diffusion time, which is much longer than the quasilinear diffusion time. Final time in this video, normalized to the plasma frequency: 2400. More on the code: M. Lesur, Y. Idomura, and X. Garbet, Fully nonlinear features of the energy beamdriven instability, Phys. Plasmas 16, 092305 (2009). More on the model: M. Lesur, The BerkBreizman model as a paradigm for energetic particledriven Alfvén eigenmodes, PhD Thesis (2011). Thanks! 
Re: Phasespace structures in plasma turbulence
Interesting thesis.
One might find this book of interest. http://www.physics.ucsd.edu/~tmurphy.../BookFINAL.pdf With respect to: Quote:

Re: Phasespace structures in plasma turbulence
Thank you!
Actually it is this very book that inspired my current work. Very insightful indeed. On the theory side at least. The first author of this book is also a coauthor of a paper I'm writing on a related topic. I'll post the paper here when it's published. However, in this book I didn't find any example of experimental study of the effect of phasespace structures (granulations) on turbulent astrophysical systems. One example, which shows striking similarities with phasespace structures in turbulent plasmas, is zonal flow in quasigeostrophic systems, such as Jupiter. However, the structures live in real space, not in phasespace. The equations of conservation of potential vorticity and phasespace density (the QG equation and the Vlasov equation) are similar, but there's an important qualitative difference in the Hamiltonian, which makes me doubt we can expect similar physics. 
All times are GMT 5. The time now is 12:28 PM. 
Powered by vBulletin Copyright ©2000  2014, Jelsoft Enterprises Ltd.
© 2014 Physics Forums