arXiv 1008.28932010-08astro-ph.SR

太阳风等离子体中横离子回旋波与离子的相互作用

On the interactions of transverse ion-cyclotron waves with ions in solar wind plasma

Sofiane Bourouaine, Eckart Marsch, Fritz M. Neubauer

摘要：

我们利用Helios数据证明了太阳风等离子体中存在离子回旋耗散机制。从我们的统计分析中，我们发现，高频横波的波功率（具有在等离子体帧中归一化为质子回旋频率的0.01和1之间的频率）与质子温度各向异性，$T_{\perp}/T_{\parallel}$，和归一化的差分速度，$V_{αp}/V_A$，α粒子和质子之间的相关。此外，当该速度保持低于0.5时，α粒子温度各向异性与横波的相对功率正相关。然而，如果$V_{αp}/V_A$大于0.6，则α粒子温度各向异性倾向于朝向低于1的值减小，尽管存在具有相对大振幅的横波。对于较小的相对波振幅，当α粒子与电子的密度比接近或低于0.01时，α粒子甚至可以比质子更强烈地被加热。我们的研究结果是在很好的协议与动力学理论的预测共振相互作用的离子与阿尔文回旋波和由此产生的波耗散。此外，研究表明，湍流可能导致平行阿尔芬回旋波的产生。

英文摘要：

We show the evidence of ion-cyclotron dissipation mechanism in solar wind plasma using Helios data. From our statistical analysis we found that the wave power of high-frequency transverse waves (having frequencies between 0.01 and 1 normalized to the proton gyrofrequency in the plasma frame) correlates with both, the proton temperature anisotropy, $T_{\perp}/T_{\parallel}$, and the normalized differential speed, $V_{αp}/V_A$, between alpha particles and protons. Furthermore, when this speed stays below 0.5, then the alpha-particle temperature anisotropy correlate positively with the relative power of the transverse waves. However, if $V_{αp}/V_A$ is larger than 0.6, then the alpha-particle temperature anisotropy tends to decrease towards values below unity, despite the presence of transverse waves with relatively large amplitudes. For small relative wave amplitude, it is found that alpha particles can even be heated more strongly than protons when the alpha-to-electron density ratio nearly or below 0.01. Our findings are in good agreement with predictions of kinetic theory for the resonant interaction of ions with Alfvén-cyclotron waves and for the resulting wave dissipation. Also, the study suggests that the turbulence could lead to the generation of parallel Alfven cyclotron waves.

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