1 / 16

Coronal heating by low frequency wave-driven quasi-2D MHD turbulence cascade

Explore the physics of coronal turbulence using various models and examine the mechanisms of low-frequency wave-driven heating. The study investigates different geometric and physical setups to analyze the sustained turbulent dissipation and efficiency of heating rates.

loriroberts
Download Presentation

Coronal heating by low frequency wave-driven quasi-2D MHD turbulence cascade

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Coronal heating by low frequency wave-driven quasi-2D MHD turbulence cascade W. H. Matthaeus SHINE 2007 – Whistler BC 30 July 2007

  2. Will use four types of models of basic physics of coronal turbulence: • “box” models • Phenomenological models • Full RMHD in expanding geometry • Compressible 3D MHD periodic geometry

  3. Parker (1972), Priest et al (1998), Einaudi et al (1996)... Parker (1991), Axford and McKenzie (1995)

  4. [McKenzie et al, 1995; Axford and McKenzie, 1997]

  5. Incoming wave Refracted wave Region of shear B0 K3 u ¢r u K2 Modulated at frequency = (K3-K1)¢ B0 K1 B0 K3 If K2¢B0 = 0 this is  = 0 interaction K2 K1

  6. Model: - Low frequency waves propagate upwards at the coronal base - Inhomogeneity cause REFLECTION - Counterpropagating interact, drive a low frequency “Reduced MHD” cascade - Turbulent dissipation is sustained; Efficiency = Turbulent Dissipation/Flux Supplied Rate of transmission: Alfven Speed / parallel “box” length Rate of Reflection: Rate of turbulent dissipation

  7. Coronal phenomenology • Detail of transverse structure is suppressed -- modeled by turbulence phenomenology • Perpendicular energy containing (correlation) scale controls turbulence • Propagation, reflection and boundary effects are like 1D waves

  8. RMHD (Box): Broadband spectra, random transient reconnection/current sheets T=100 Magnetic field and current density Velocity field and vorticity PDF of Electric current density: Intermittency

  9. Efficiency of 10-50% or moderate to high R, fixed T=1 Dissipation --> 0 if R=0 But Steady dissipation is insensitive to initial seed turbulence level Box model with R and T RMHD simulation Phenomenology

  10. RMHD simulation with coronal profile • Radial expansion • R=Rm=600 • Forcing at bottom • single low frequency 0.1/TA • broadband in Kperp • Waves escape from top and bottom

  11. Comparison of three simulations Comparison of three expansion/RMHD simulations with different density profiles Heating/volume is ~exponentially confined

  12. Conclusions: low frequency wave-driven MHD turbulence as a candidate mechanism for heating the open field line corona • Low frequency waves + reflection = RMHD cascade = sustained turbulent heating • Turbulent heating is insensitive to • initial conditions • many details of the fluctuations • Turbulent heating is sensitive to • reflection • boundary conditions --- “non-propagating “ modes • Heat function • determined by coronal density profiles • approximately exponential with L= Rsun/3 for isothermal gravitationally stratified atmosphere • Efficiencies of 10% - 50 % are easily attainable • Kinetic mechanisms to absorb energy at high kperp are not yet identified

  13. TEST PARTICLE Protons after ~1 nonlinear time Highperpendicular energy B0 B0 TEST PARTICLE Electrons after ~1/10 nonlinear time High parallel energy Out of page B0 B0

  14. Coronal heating by low frequency/quasistatic driven cascade is promising Can we develop a full coronal model that converts low frequency wave energy into a turbulent cascade that produces rapid and sustained heating?Can a model of this type accelerate the wind?Can a model of this type produce the observed kinetic plasma signatures? self consistent models are needed!

More Related