产生次声的流星的光学观测- I：声学信号识别和现象学
Optical Observations of Meteors Generating Infrasound - I: Acoustic Signal Identification and Phenomenology
摘要：
我们分析了从71个明亮的流星同时检测到的视频次声信号，研究流星产生的近场次声和冲击生产的现象和特点。利用次声波到达的时间-压力信号，提出了一种流星次声波信号分类方法。根据沿流星轨迹次声信号起源的位置，我们发现大多数信号与圆柱形冲击，约四分之一的事件证明与碎裂事件和光学耀斑有关的球形冲击。视频数据表明，射线发射角>117度的事件最有可能是由球形激波产生的，而射线发射角<117度的流星产生的次声可以归因于圆柱形线源和球形激波。我们发现，流星优先生产次声对他们的踪迹结束与少数显示出偏好中期的踪迹生产。流星产生多个次声波到达显示出强烈的次声源高度偏斜的轨迹结束，更有可能与光学耀斑。虽然我们的流星中有很大一部分产生了次声波（~1/4的单次到达）是由碎裂事件产生的，我们没有发现在我们的流星体大小的弹道制度以外超过约60度可探测到的声辐射的例子（克至数十公斤）强调流星声辐射的强各向异性，其中以圆柱形线源几何形状为主，即使存在碎片。
英文摘要：
We analyze infrasound signals from 71 bright meteors simultaneously detected by video to investigate the phenomenology and characteristics of meteor-generated near-field infrasound and shock production. A taxonomy for meteor generated infrasound signal classification has been developed using the time-pressure signal of the infrasound arrivals. Based on the location along the meteor trail where the infrasound signal originates, we find most signals are associated with cylindrical shocks, with about a quarter of events evidencing spherical shocks associated with fragmentation events and optical flares. The video data indicate that all events with ray launch angles >117 deg from the trajectory heading are most likely generated by a spherical shock, while infrasound produced by the meteors with ray launch angles <117 deg can be attributed to both a cylindrical line source and a spherical shock. We find that meteors preferentially produce infrasound toward the end of their trails with a smaller number showing a preference for mid-trail production. Meteors producing multiple infrasound arrivals show a strong infrasound source height skewness to the end of trails and are much more likely to be associated with optical flares. While a significant fraction of our meteors producing infrasound (~1/4 of single arrivals) are produced by fragmentation events, we find no instances where acoustic radiation is detectable more than about 60 deg beyond the ballistic regime at our meteoroid sizes (grams to tens of kg) emphasizing the strong anisotropy in acoustic radiation for meteors which are dominated by cylindrical line source geometry, even in the presence of fragmentation.
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