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Nonresonant pitch angle scattering of electrons and breakdown of adiabatic invariance: Modeling

Nonresonant pitch angle scattering of electrons and breakdown of adiabatic invariance: Modeling. Surja Sharma, Alexey Karavaev, Erin Lynch , Nail Gumerov, Xi Shao, Dennis Papadopoulos University of Maryland, College Park. Yuhou Wang , Walter Gekelman, Patrick Pribyl

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Nonresonant pitch angle scattering of electrons and breakdown of adiabatic invariance: Modeling

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  1. Nonresonant pitch angle scattering of electrons and breakdown of adiabatic invariance: Modeling Surja Sharma, Alexey Karavaev, Erin Lynch, Nail Gumerov, Xi Shao, Dennis Papadopoulos University of Maryland, College Park Yuhou Wang, Walter Gekelman, Patrick Pribyl University of California Los Angeles

  2. LAPD Expt: Mirror trapped electrons 3 m mirror (~1.5), high power microwave produces energetic electrons Alfven waves produced by rotating magnetic field antenna scatters energetic electrons

  3. Numerical Simulations

  4. Simulation parameters

  5. Alfven wave generation by RMF Mirror configuration Magnetic field Electric field

  6. Energization of electrons Test particles 22,500 electrons uniformly distributed in the mirror region Initial pitch angles : 80 – 90 deg Initial energies: 1 keV Integrate:

  7. Evolution of Pitch Angles

  8. Electron scattering Resonance condition: For the low freq. and keV energy: Non-resonant scattering

  9. Spatial distribution of electrons At 25 wave periods Single loop antenna RMF - Left hand polarization RMF - Right hand polarization

  10. Evolution of Pitch Angles

  11. Surface of Section Plots A surface of section (SoS) plots Vperp vs. Vpar as an electron crosses the plane x = 0 from right to left. Escaped electron

  12. SoS: Trapped electron • Here is a similar plot for another particle that did not escape.

  13. SoS: Escaping electron • This surface of section depicts a particle that did escape from the simulation.

  14. SoS : 5 wave cycles

  15. SoS: 10 wave cycles

  16. SoS: 25 wave cycles

  17. Surfaces of Section 5 wave cycles 10 wave cycles 25 wave cycles

  18. Pitch angle distribution functions Single loop antenna Rotating Field: Left and Right handed

  19. Summary Interaction of energetic electrons with RMF generated Alfven waves Electron scattering by Alfven waves computed from numerical model Nonresonant scattering leads to pitch angle scattering Surface of section plots to analyze electron velocity evolution Trapped electrons escape at ~ 10 wave periods Combined effects of the pitch angle scattering and breakdown of adiabatic invariance

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