An entry model for the Tagish Lake fireball using seismic, satellite and infrasound records
An entry model for the Tagish Lake fireball using seismic, satellite and infrasound records
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使用地震、卫星和次声记录的塔吉什湖火球入口模型
DOI：
10.1111/j.1945-5100.2002.tb00846.x
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发表时间：
2002
影响因子：
2.2
通讯作者：
A. Hildebrand
中科院分区：
文献类型：
--
作者：
P. Brown;D. Revelle;E. Tagliaferri;A. Hildebrand
摘要：我们提出了对塔吉什湖火球的仪器观测，并在两种不同的消融模型的背景下解释了观测到的特征。根据这些模型，我们估计塔吉什湖流星体的大气层前质量约为 56 吨，其孔隙度在 37% 至 58% 之间，最有可能是该范围的最低部分。这些模型进一步表明，约 1300 公斤克级或更大的塔吉什湖物质在烧蚀后幸存下来并到达地球表面，这意味着火球烧蚀损失了 97%。塔吉什湖火球的卫星记录表明，火球在其飞行的最后 4 秒内发射了 1.1 倍 1012 J 的光能。发现卫星通带内转换为光的总动能的比例为 16%。对与火球相关的空气波的次声波观测确定了该事件的总能量为 1.66 ± 0.70 kT TNT 等效能量。发现转换为声信号能量的总能量的比例在 0.10% 到 0.23% 之间。对塔吉什湖电波地震记录的检查表明，子终点附近的声能在地壳最上部转化为地震体波。塔吉什湖火球的声能与地震能量耦合效率接近 10−6。由此产生的能量估计接近 1.7 kT，对应于直径 4 m 的流星体。地震记录表明，在 50 至 32 公里的高度区间内，该物体发生了广泛的、几乎连续的破碎。地震和次声能量估计与根据模型建立的 56 吨大气前质量非常一致。观测到的塔吉什湖火球的飞行特征表明，塔吉什湖流星体大气前的体积抗压强度接近0.25 MPa，而材料抗压强度（最适合回收的陨石）接近0.7 MPa。这些值远低于普通球粒陨石成分的火球的值。塔吉什湖火球的行为表明它代表了碳质球粒陨石强度谱的最低端或彗星流星体的高端。塔吉什湖流星体的体积密度和孔隙度结果表明，太阳系中一些小型原始天体测得的低体积密度可能反映了以微孔隙而不是大孔隙和碎石堆组合为主的物理结构。
Abstract— We present instrumental observations of the Tagish Lake fireball and interpret the observed characteristics in the context of two different models of ablation. From these models we estimate the pre‐atmospheric mass of the Tagish Lake meteoroid to be ˜56 tonnes and its porosity to be between 37 and 58%, with the lowest part of this range most probable. These models further suggest that some 1300 kg of gram‐sized or larger Tagish Lake material survived ablation to reach the Earth's surface, representing an ablation loss of 97% for the fireball. Satellite recordings of the Tagish Lake fireball indicate that 1.1 times 1012 J of optical energy were emitted by the fireball during the last 4 s of its flight. The fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16%. Infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1.66 ± 0.70 kT TNT equivalent energy. The fraction of this total energy converted to acoustic signal energy is found to be between 0.10 and 0.23%. Examination of the seismic recordings of the airwave from Tagish Lake have established that the acoustic energy near the sub‐terminal point is converted to seismic body waves in the upper‐most portion of the Earth's crust. The acoustic energy to seismic energy coupling efficiency is found to be near 10−6 for the Tagish Lake fireball. The resulting energy estimate is near 1.7 kT, corresponding to a meteoroid 4 m in diameter. The seismic record indicates extensive, nearly continuous fragmentation of the body over the height intervals from 50 to 32 km. Seismic and infrasound energy estimates are in close agreement with the pre‐atmospheric mass of 56 tonnes established from the modeling. The observed flight characteristics of the Tagish Lake fireball indicate that the bulk compressive strength of the pre‐atmospheric Tagish Lake meteoroid was near 0.25 MPa, while the material compressive strength (most appropriate to the recovered meteorites) was closer to 0.7 MPa. These are much lower than values found for fireballs of ordinary chondritic composition. The behavior of the Tagish Lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids. The bulk density and porosity results for the Tagish Lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble‐pile assemblages.