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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >On the cascade processes of Alfven waves in the fast solar wind
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On the cascade processes of Alfven waves in the fast solar wind

机译：关于太阳快速风中阿尔夫文波的级联过程

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We present a numerical study which explores the nonlinear cascade effect associated with Alfven waves in the fast solar wind. The set of one-dimensional, two-fluid equations describing the solar wind and a power spectrum equation for Alfven waves, as first proposed by Tu et al. [1984], are solved simultaneously in a self-consistent manner. Both Kolmogorov and Kraichnan cascade functions, which vary as f~(5/2)P~(3/2) and f~3P~2, respectively, are considered. For an Alfven wave spectrum at the coronal base, which is flat in the low-frequency range and has a slope of -1 in the high-frequency range, the Kolmogorov cascade function reproduces the Alfven wave spectrum observed beyond 0.29 AU very well. The Kraichnan cascade function, on the other hand, yields a spectrum that is within the 90% confidence level of the observed values. Both cascade functions yield a gradually accelerating fast solar wind in the inner corona, typical of wave acceleration models. The results of this first solar wind model which describes, in a self-consistent manner, the evolution of the wave spectrum and cascade in the inner corona confirm conclusions reached by earlier studies, namely, that the Kolmogorov process produces a stronger cascade effect than the Kraichnan process and seems more relevant for Alfven waves in the fast solar wind, at least beyond 0.29 AU. The approach shows that Alfven waves, with periods of hours or shorter, undergo an appreciable evolution from the solar surface to 1 AU, thus implying that their spectrum; hence their total energy flux at the Sun cannot be readily predicted from that observed in interplanetary space.
机译：我们提出了一个数值研究，探讨了在快速太阳风中与阿尔夫文波有关的非线性级联效应。 Tu等人首先提出的描述太阳风的一维，两流体方程组和Alfven波的功率谱方程组。 （1984），以自洽的方式同时解决。考虑了Kolmogorov和Kraichnan级联函数，它们分别随着f〜（5/2）P〜（3/2）和f〜3P〜2而变化。对于在低频范围内平坦且在高频范围内具有-1斜率的日冕基础上的Alfven波谱，Kolmogorov级联函数很好地再现了观察到的0.29 AU以上的Alfven波谱。另一方面，Kraichnan级联函数产生的光谱在观测值的90％置信度内。这两个级联函数都会在内部电晕中产生逐渐加速的快速太阳风，这是波浪加速模型的典型特征。该第一个太阳风模型的结果以自洽的方式描述了内部电晕中的波谱和级联的演化，证实了早期研究得出的结论，即，Kolmogorov过程产生的级联效应要比前者强。 Kraichnan过程似乎与快速太阳风中的Alfven波相关，至少超过0.29 AU。该方法表明，小时数或更短的Alfven波从太阳表面到1 AU发生了明显的演化，从而暗示了它们的光谱。因此，不能轻易地从在行星际空间中观察到的能量来预测它们在太阳处的总能量通量。

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