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Wave and Plasma Simulations: Resonant Effects

Wave and Plasma Simulations: Resonant Effects. By John Lazos. The Sun’s Winds. Hot solar wind blows out. The wind is charged particles. A Plasma with few collisions. MAGNETIZED WIND. Carries Magnetic Field. Magnetized waves travel out. Alfven Waves. MOST IMPORTANT WAVE

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Wave and Plasma Simulations: Resonant Effects

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  1. Wave and Plasma Simulations:Resonant Effects By John Lazos

  2. The Sun’s Winds • Hot solar wind blows out. • The wind is charged particles. • A Plasma with few collisions.

  3. MAGNETIZED WIND • Carries Magnetic Field. • Magnetized waves travel out.

  4. Alfven Waves • MOST IMPORTANT WAVE • Undamped by the plasma • So, travels far.

  5. Resonance • Singer breaking glass • Critical phenomenon in physics and engineering

  6. Space Physics Resonances • Waves moving at same speed • Particles moving with the waves • These are all in resonance

  7. Resonances We Study 1. Alfven Wave Steepening 2. Alfven Wave Decay 3. Ion Beam Slowdown • Solar Wind = Charged Particles • Need Technique for Particles

  8. This is our technique: Hybrid Simulations • Ions = Particles • Electrons = Fluid *Treats a real collisionless solar wind plasma

  9. 1st Simulation Project: Wave Steepening • Alfven wave like string wave • Propagates down string; string = magnetic field

  10. Nonlinear Steepening in Cool Plasma • Magnetic Intensity varies • Resonance of two magnetized waves • Results in steepening

  11. Prediction by Analysis on Paper COOL HOT • ß = ratio of sound speed squared to the Alfven speed squared. (Cool to Hot) VALID HERE ß FAILS: Triple Resonance

  12. Scientific Objective #1 • Measure steepening time near ß = 1 and higher. • This can only be done with a numerical simulation.

  13. Simulation Results ß Sound wave Punches Alfven wave ahead ß = 1 4X faster than in cool plasma

  14. 2nd Simulation Project: Wave Decay • Total Intensity = Constant • NO Steepening • Happens Naturally for wave travel along and across magnetic field • This wave is an Arc-Wave.

  15. Arc-Wave Travels OUT of paper

  16. Arc-Wave could travel without changing form. • But the slightest noise kills it.

  17. Explosion of New Waves New Growing Wave Noise

  18. Arc-Wave Collapses • Energy for the new waves comes from the original Arc-Wave. • These new waves are resonant and take so much from the arc-wave that the arc-wave dies.

  19. Scientific Objective #2 • Quantify rate of fastest growing new wave. • Plot as a function of ß. • ONLY simulations can find these answers.

  20. Fourier Analysis Slope gives rate Finds amplitude for each cycle

  21. Simulation Results ß The colder the plasma, the faster the Arc-Wave dies.

  22. 3rd Simulation Project: Beam Slowdown • In the Solar Wind, Helium streams faster than Protons. • Wave-Particle resonances have consequences here.

  23. What we are doing: • Drive a Helium beam through Protons. • Above a critical speed, waves from noise will resonate with Helium. • Helium slows down as waves steal energy.

  24. Scientific Objective #3 • Find the critical speed where the beam generates new waves.

  25. Simulation Results PLOTS OF STREAMING SPEED vs. TIME • Fast, supercritical beam. (U = 2.3*VA) • Slower, marginally critical beam. (U = 1.8*VA)

  26. Conclusions 1. When ß = 1, wave steepens 4 x faster than in cool plasma. 2. Arc-Wave decays faster in colder plasma. 3. Beam slowdown occurs above U = 1.8*VA (1.8 times the Alfven speed).

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