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首页> 外文学位 >Suppression of nonlinear frequency sweeping of resonant interchange modes in a magnetic dipole with applied radio frequency fields.
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Suppression of nonlinear frequency sweeping of resonant interchange modes in a magnetic dipole with applied radio frequency fields.

机译：施加电磁场的电磁偶极子中共振交换模式的非线性扫频的抑制。

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摘要

Interchange instabilities excited by energetic electrons trapped by a magnetic dipole nonlinearly saturate and exhibit complex, coherent spectral characteristics and frequency sweeping. When monochromatic radio frequency (RF) fields are applied in the range of 100–1000 MHz, the saturation behavior of the interchange instability changes dramatically. For applied fields of sufficient intensity and pulse-length, coherent interchange fluctuations are suppressed and frequency-sweeping is eliminated. When RF fields are switched off, coherent frequency-sweeping reappears. Since low-frequency interchange instabilities preserve the electron's first and second adiabatic invariants, these observations can be interpreted as resulting from nonlinear resonant wave-particle interactions described within a particle phase-space, (ψ, ϕ), comprised of the third adiabatic invariant, ψ, and the azimuthal angle, ϕ. The frequency-sweeping suppression is understood to result from electron-cyclotron resonant diffusion of energetic electrons in μ-direction, as reproduced by the numerical simulation. Self-consistent numerical simulation is used to study (1) the nonlinear development of the instability, (2) the radial mode structure of the interchange instability, and (3) the suppression of frequency-sweeping. When the applied RF heating is modeled as an “RF collisionality,” the simulation reproduces frequency-sweeping suppression and suggests an explanation for the observations that is consistent with the nonlinear theory by H. Berk and co-workers.
机译：由磁偶极子捕获的高能电子激发的交换不稳定性会非线性饱和，并表现出复杂的相干光谱特性和扫频特性。当在100-1000 MHz范围内应用单色射频（RF）场时，交换​​不稳定性的饱和行为会发生巨大变化。对于具有足够强度和脉冲长度的应用场，可以抑制相干互换波动并消除扫频。当RF场关闭时，会再次出现相干扫频。由于低频交换不稳定性保留了电子的第一绝热和第二绝热不变量，因此这些观察结果可以解释为由粒子相空间（ψ，＆phiv）中描述的非线性共振波-粒子相互作用引起的，该粒子由第三绝热不变量组成，ψ和方位角＆phiv;。扫频抑制被理解为是由于高能电子在μ方向上的电子回旋共振扩散而产生的，如通过数值模拟再现的。自洽数值模拟用于研究（1）不稳定性的非线性发展，（2）互换不稳定性的径向模式结构，以及（3）扫频的抑制。当将施加的RF加热建模为“ RF碰撞性”时，该模拟会重现扫频抑制作用，并为观察结果提供与H. Berk及其同事的非线性理论一致的解释。

著录项

  • 作者

    Maslovsky, Dmitry Anatolievich.;

  • 作者单位

    Columbia University.;

  • 授予单位 Columbia University.;
  • 学科 Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 p.784
  • 总页数 100
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 等离子体物理学;
  • 关键词

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