Helium ion acceleration and heating by Alfvén/cyclotron fluctuations in the solar wind
Helium ion acceleration and heating by Alfvén/cyclotron fluctuations in the solar wind
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DOI：
10.1029/2001ja000059
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发表时间：
2001-11
期刊：
影响因子：
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通讯作者：
S. Gary;B. Goldstein;J. Steinberg
中科院分区：
文献类型：
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作者：
S. Gary;B. Goldstein;J. Steinberg
在均匀、无碰撞、磁化的等离子体模型中，研究了在平行于背景磁场Bo传播时，α粒子与给定的Alfvén/回旋涨落的磁功率谱之间的相互作用。利用线性Vlasov色散方程的精确解和二阶理论，计算了α/质子动量交换、质子和α加热以及各向异性变化的波粒散射率。众所周知，当平行于Bo的α/质子相对速度与长波Alfvén波的相速度，即“冲浪”速度相匹配时，不会观察到α速度的振荡。二阶理论预言，波粒散射主要由相对较短波长、相对较低相速度的Alfvén/回旋涨落主导，这些涨落与Alpha有很强的回旋共振。因此，该理论预测，在足够高的质子β下，观测到的平均α/质子速度应该比与长波长波动相关的冲浪速度小得多。
The interaction between alpha particles and a given magnetic power spectrum of Alfvén/cyclotron fluctuations at propagation parallel to the background magnetic field Bo is examined in a model of a homogeneous, collisionless, magnetized plasma. Exact solutions of the linear Vlasov dispersion equation and second‐order theory are used to calculate the wave‐particle scattering rates for alpha/proton momentum exchange as well as for proton and alpha heating and anisotropy change. It is well established that alpha velocities are not observed to oscillate when the alpha/proton relative flow speed parallel to Bo matches the phase speed of long‐wavelength Alfvén waves, the “surfing” speed. Second‐order theory predicts that wave‐particle scattering is dominated by the relatively short wavelength, relatively low phase speed Alfvén/cyclotron fluctuations which have a strong cyclotron resonance with the alphas. Thus the theory predicts that at sufficiently high proton β the average alpha/proton speed should be observed to be substantially smaller than the surfing speed associated with long‐wavelength fluctuations.