Phase-space structures in plasma turbulence

In summary, phase-space structures in turbulent astrophysical systems seem to be much more complex and intriguing than what is found in this book.
  • #1
maxime.lesur
11
0
Here is a glimpse of my current research. This is a kinetic simulation of electrostatic waves in a bump-on-tail plasma, with multiple resonances and some dissipation. Quasi-linear theory predicts a flattening of the velocity distribution over the range of resonant velocities of linearly unstable modes. However, self-coherent phase-spaces 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 co-existing 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 phase-space structures on turbulence?

More on this simulation:
Nonlinear growth, evolution and interaction of self-coherent phase-space structures in a dissipative bump-on-tail plasma simulation with multiple resonances, using the kinetic code COBBLES. Up: perturbed distribution function. Down: spatially-averaged 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.
Quasi-linear theory predicts a flattening of the velocity distribution over the range of resonant velocities of linearly unstable modes. However, self-coherent phase-spaces 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 phase-space structures survive for a collisional diffusion time, which is much longer than the quasi-linear 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 beam-driven instability, Phys. Plasmas 16, 092305 (2009).

More on the model: M. Lesur, The Berk-Breizman model as a paradigm for energetic particle-driven Alfvén eigenmodes, PhD Thesis (2011).

Thanks!
 
Astronomy news on Phys.org
  • #2
Interesting thesis.

One might find this book of interest.
http://www.physics.ucsd.edu/~tmurphy/phys239/BookFINAL.pdf [Broken]

With respect to:
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 phase-space structures on turbulence?
I believe that CMEs (and flares and prominences) and solar helioseismology (turbulence) involved investigation of nonlinear effects of phase-space structures.
 
Last edited by a moderator:
  • #3
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 co-author 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 phase-space structures (granulations) on turbulent astrophysical systems.

One example, which shows striking similarities with phase-space structures in turbulent plasmas, is zonal flow in quasi-geostrophic systems, such as Jupiter. However, the structures live in real space, not in phase-space. The equations of conservation of potential vorticity and phase-space 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.
 

1. What are phase-space structures in plasma turbulence?

Phase-space structures in plasma turbulence refer to localized regions of high or low energy density in the plasma. These structures can take various forms, such as vortices, filaments, or solitons, and are characterized by their distinct spatial and temporal scales.

2. How do phase-space structures form in plasma turbulence?

Phase-space structures in plasma turbulence are formed through the nonlinear interactions between different plasma waves. These interactions can lead to the concentration of energy in certain regions, resulting in the formation of localized structures.

3. What role do phase-space structures play in plasma turbulence?

Phase-space structures are important features of plasma turbulence, as they can affect the transport and dissipation of energy in the plasma. They can also impact the dynamics of the plasma, leading to phenomena such as turbulence suppression or enhanced particle acceleration.

4. Can phase-space structures be observed in experiments or simulations?

Yes, phase-space structures have been observed in both laboratory experiments and numerical simulations of plasma turbulence. These observations have provided valuable insights into the properties and behavior of these structures.

5. How do phase-space structures impact plasma confinement and stability?

Phase-space structures can have a significant impact on plasma confinement and stability. They can cause fluctuations and transport of particles and energy, which can affect the overall stability and confinement of the plasma. Understanding and controlling these structures is crucial for achieving optimal plasma performance in fusion devices.

Similar threads

  • High Energy, Nuclear, Particle Physics
Replies
2
Views
1K
  • STEM Academic Advising
Replies
4
Views
2K
  • Astronomy and Astrophysics
Replies
8
Views
4K
  • Cosmology
Replies
2
Views
2K
  • STEM Academic Advising
Replies
6
Views
1K
  • General Discussion
Replies
2
Views
3K
  • Beyond the Standard Models
Replies
2
Views
11K
  • STEM Academic Advising
Replies
6
Views
8K
Back
Top