Abstract. We present a statistical survey of large amplitude, asymmetric plasma, and magnetic field enhancements at comet 67P/Churyumov-Gerasimenko from December 2014 to June 2016. The aim is to provide a general overview of these structures' properties over the mission duration. At comets, nonlinear wave evolution plays an integral part in the development of turbulence and in particular facilitates the transfer of energy and momentum. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of steepened waves and their characteristics. In total, we identified ~70000 events in the magnetic field data by means of machine learning. We observe that the occurrence of wave events is linked to the activity of the comet, where events are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressive nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual events. With increasing massloading the average amplitude of steepened waves decreases while the skewness increases. Using a modified 1D MHD model it was possible to show that such solitary structures can be described by the combination of nonlinear, dispersive, and dissipative effects. By combining the model with observations of amplitude, width, and skewness we obtain an estimate of the effective plasma viscosity in the comet-solar wind interaction region. At 67P/Churyumov-Gerasimenko steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

中文翻译：

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彗星67P / Churyumov-Gerasimenko彗星内慧中的磁声波变陡

摘要。我们提供了2014年12月至2016年6月在67P / Churyumov-Gerasimenko彗星上出现的大振幅，不对称等离子体和磁场增强的统计调查。目的是在任务期间全面概述这些结构的特性。在彗星上，非线性波的演化在湍流的发展中起着不可或缺的作用，特别是促进了能量和动量的传递。作为此类任务的第一个任务，ESA Rosetta任务能够长时间地以及在活动的不同阶段研究内昏迷的血浆特性。这使我们能够研究陡峭波的时间演化及其特征。总体而言，我们通过机器学习在磁场数据中识别出约700,000个事件。我们观察到波浪事件的发生与彗星的活动有关，而彗星的活动主要是在高除气率下观察到的。没有发现发生率与太阳风状况之间关系的明确迹象。发现这些波主要垂直于背景磁场传播，这表明它们具有压缩性质。通过将偏斜正态分布拟合到单个事件的磁场强度中，可以提取出诸如振幅，偏度和波宽度之类的特征。随着质量载荷的增加，陡峭波的平均振幅减小，而偏斜度增加。使用修改后的一维MHD模型，有可能表明可以通过非线性，色散和耗散效应的组合来描述这种孤立的结构。通过将模型与振幅，宽度和偏度的观测值结合起来，我们获得了彗星-太阳风相互作用区域中有效等离子体粘度的估计值。在67P / Churyumov-Gerasimenko，陡峭的波浪尤为重要，因为它们支配了最中间的相互作用区域，从而实现了中高活动。