维持地球和火星上风沙所需的最小风速的分析计算
Analytical calculation of the minimum wind speed required to sustain wind-blown sand on Earth and Mars
摘要：
沙粒在风的驱动下跳跃运动，即所谓的跳跃，形成沙丘和涟漪，并将细小的尘埃颗粒带入地球和火星的大气层。虽然已经对跳跃开始时的风速（流体阈值）进行了广泛的研究，但对火星条件下跳跃停止时的风速（撞击阈值）却没有进行很好的量化。我们提出了一个分析模型的影响阈值，我们表明是在协议的测量和最近的地球条件下的数值模拟。对于火星的条件下，我们发现，影响阈值大约是一个数量级低于流体阈值，与以前的研究一致。因此，火星上的跳跃可以在比启动它所需的风速低一个数量级的情况下维持，从而导致滞后现象的发生。这些结果证实了早期的模拟与详细的数值跃移模型，并有重要意义的沙丘，涟漪和沙尘暴在火星上的形成。
英文摘要：
The wind-driven hopping motion of sand grains, known as saltation, forms dunes and ripples and ejects fine dust particles into the atmosphere on both Earth and Mars. While the wind speed at which saltation is initiated, the fluid threshold, has been studied extensively, the wind speed at which it is halted, the impact threshold, has been poorly quantified for Mars conditions. We present an analytical model of the impact threshold, which we show to be in agreement with measurements and recent numerical simulations for Earth conditions. For Mars conditions, we find that the impact threshold is approximately an order of magnitude below the fluid threshold, in agreement with previous studies. Saltation on Mars can thus be sustained at wind speeds an order of magnitude less than required to initiate it, leading to the occurrence of hysteresis. These results confirm earlier simulations with a detailed numerical saltation model, and have important implications for the formation of sand dunes, ripples, and dust storms on Mars.
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