L'Aigle: The Fragment Statistics of the Shower That Settled the Origin of Meteorites

This paper computes a complete entry budget for the L'Aigle shower, working only from published values and stated assumptions. The nominal body has a diameter of 0.35 metres at a bulk density of 3.40e+03 kilograms per cubic metre, giving an incoming mass of 0.0763 tonnes. At the published entry speed of 13 kilometres per second its kinetic energy is 1.54e-03 kilotonnes of TNT equivalent. At the characteristic altitude of 20 kilometres the exponential atmosphere has a density of 0.0762 kilograms per cubic metre, the ram pressure on the body is 12.9 megapascals, the stagnation heating flux is 8.37e+04 megawatts per square metre, and the aerodynamic deceleration is 1.65e+03 times terrestrial gravity. The ram pressure first reaches representative material strengths at computed altitudes of 55, 38.4 and 26.8 kilometres for the weakest, intermediate and strongest cases examined. The recovered material, the stones collected and catalogued after the shower, amounts to 37 kilograms, which is 48.5 percent of the computed incoming mass. The largest recovered piece, at 9 kilograms, has a characteristic diameter of 17.2 centimetres, a terminal velocity of 115 metres per second, a fall time of 86.9 seconds from the end of the luminous path at 10 kilometres, and a wind drift of 869 metres under a representative wind. Over the mapped strewn area of 8 square kilometres, the recovered mass corresponds to 4.62 kilograms per square kilometre. The fragment census gives a mean collected mass of 0.0123 kilograms per fragment. The largest stone, at 9 kilograms, carries 24.3 percent of the recovered total. All values are computed by the deposited program from the stated inputs; scenario calculations accompany every headline figure so that the sensitivity of each conclusion to its inputs is visible in the same record.