标题： 良好视宁度序列的典型持续时间 显示英文标题

标题： Typical duration of good seeing sequences at Concordia

摘要： 上下文：康科迪亚的冬季视宁度基本上是双峰的，要么很好，要么相当差，相对比例取决于离雪面的高度。 本文研究了良好视宁度序列的时间行为。 目标：为了高效利用极好的视宁度，需要使用自适应光学系统进行长时间积分。因此，探索提供良好视宁度的时间比例的时序分布是很重要的。 方法：通过一个简单的二进制过程创建良好视宁度的时间窗口。良好或不好。由于这些数据集并不连续，除了恶劣天气间隙外，还经常受到技术问题的中断，因此对它们的自相关性进行了校正。最后，这些校正后的自相关性提供了良好视宁度序列的典型持续时间。 这项研究必须稍微详细一些，因为其结果取决于季节，夏季或冬季。 结果：使用0.5角秒的阈值来定义“良好视宁度”，发现了三个特征数值来描述良好视宁度窗口的时间演变。 第一个数值是不间断良好视宁度序列的平均持续时间：在离地面8米处为$\tau_0=7.5$小时（在20米处为15小时）。 这些序列在时间上是随机分布的，衰减时间遵循负指数定律$\tau_1=29$小时（在海拔8米和20米处）。 第三个数值是两次29小时事件之间的平均时间。在8米高处为T=10天（在20米高处为5天）。 显示英文摘要

摘要： Context: The winter seeing at Concordia is essentially bimodal, excellent or quite poor, with relative proportions that depend on altitude above the snow surface. This paper studies the temporal behavior of the good seeing sequences. Aims: An efficient exploitation of extremely good seeing with an adaptive optics system needs long integrations. It is then important to explore the temporal distribution of the fraction of time providing excellent seeing. Methods: Temporal windows of good seeing are created by a simple binary process. Good or bad. Their autocorrelations are corrected for those of the existing data sets, since these are not continuous, being often interrupted by technical problems in addition to the adverse weather gaps. At the end these corrected autocorrelations provide the typical duration of good seeing sequences. This study has to be a little detailed as its results depend on the season, summer or winter. Results: Using a threshold of 0.5 arcsec to define the "good seeing", three characteristic numbers are found to describe the temporal evolution of the good seeing windows. The first number is the mean duration of an uninterrupted good seeing sequence: it is $\tau_0=7.5$ hours at 8 m above the ground (15 hours at 20 m). These sequences are randomly distributed in time, with a negative exponential law of damping time $\tau_1=29$ hours (at elevation 8 m and 20 m). The third number is the mean time between two 29 hours episodes. It is T=10 days at 8 m high (5 days at 20 m).