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

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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
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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
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Numerical Simulations
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Simulation parameters
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Alfven wave generation by RMF
Mirror configuration
Magnetic field
Electric field
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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

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Evolution of Pitch Angles
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Electron scattering

• Resonance condition

For the low freq. and keV energy
Non-resonant scattering
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Spatial distribution of electrons
At 25 wave periods
Single loop antenna
RMF - Left hand polarization
RMF - Right hand polarization
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Evolution of Pitch Angles
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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

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SoS Trapped electron

• Here is a similar plot for another particle that
  did not escape.

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SoS Escaping electron

• This surface of section depicts a particle that
  did escape from the simulation.

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SoS 5 wave cycles
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SoS 10 wave cycles
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SoS 25 wave cycles
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Surfaces of Section
5 wave cycles
10 wave cycles
25 wave cycles
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Pitch angle distribution functions
Single loop antenna
Rotating Field Left and Right handed
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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