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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Thermodynamic constraints on stochastic acceleration in compressional turbulence
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Thermodynamic constraints on stochastic acceleration in compressional turbulence

机译：压缩湍流中随机加速度的热力学约束

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摘要

Recent observations in the solar wind have revealed an important phenomenon. In circumstances where stochastic acceleration is expected, a suprathermal tail on the distribution function is formed with a common spectral shape: the spectrum is a power law in particle speed with a spectral index of -5. This common spectrum occurs in the quiet solar wind; in disturbed conditions downstream from shocks; and, in particular, throughout the heliosheath downstream from the termination shock of the solar wind currently being explored by Voyager 1. In this article, simple thermodynamic principles are applied to stochastic acceleration in compressional turbulence. The unique spectral index results when the entropy of the suprathermal tail has increased to the maximum allowable value. Relationships for the pressure in the suprathermal tail are also derived and found to be in agreement with observations. The results are shown to be consistent with the suprathermal tail arising from a cascade in energy, analogous to a turbulent cascade. The results may be applied broadly, because stochastic acceleration in compressional turbulence should be common in many astro-physical settings.
机译：最近在太阳风中的观测揭示了一个重要现象。在预期随机加速的情况下，分布函数上的超热尾部会形成具有共同的光谱形状：该光谱是粒子速度的幂律，光谱指数为-5。这种共同的光谱发生在安静的太阳风中。在冲击下游的不安状态下；特别是Voyager 1目前正在探索的太阳风终止冲击下游的整个太阳鞘层。在本文中，将简单的热力学原理应用于压缩湍流中的随机加速。当超热尾部的熵增加到最大允许值时，产生唯一的光谱指数。还推导了超热尾部压力的关系，发现与观测值一致。结果表明，与湍流级联类似，能量级联产生的超热尾部是一致的。该结果可能会得到广泛应用，因为在许多天体物理环境中，压缩湍流中的随机加速度应该很常见。

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