On October 8, 2011 the Earth crossed dust trails ejected from comet 21P/Giacobini-Zinner in the late 19th and early 20 th Century. This gave rise to an outburst in the activity of the October Draconid meteor shower, and an international team was organized to analyze this event. The SPanish Meteor Network (SPMN) joined this initiative and recorded the October Draconids by means of low light level CCD cameras. In addition, spectroscopic observations were carried out. Tens of multi-station meteor trails were recorded, including an extraordinarily bright October Draconid fireball (absolute mag. -10.5) that was simultaneously imaged from three SPMN meteor observing stations located in Andalusia. Its spectrum was obtained, showing a clear evolution in the relative intensity of emission lines as the fireball penetrated deeper into the atmosphere. Here we focus on the analysis of this remarkable spectrum, but also discuss the atmospheric trajectory, atmospheric penetration, and orbital data computed for this bolide which was probably released during 21P/Giacobini-Zinner return to perihelion in 1907. The spectrum is discussed together with the tensile strength for the October Draconid meteoroids. The chemical profile evolution of the main rocky elements for this extremely bright bolide is compared with the elemental abundances obtained for 5 October Draconid fireballs also recorded during our spectroscopic campaign but observed only at a single station. Significant chemical heterogeneity between the small meteoroids is found as we should expect for cometary aggregates being formed by diverse dust components.
Abstract.Results of the detailed analysis of the luminosity and ablation of bright Taurid, that break up into individual pieces in the Earth's atmosphere due to the aerodynamic pressure are presented. The aim of this analysis is to determine the composition and strength of Taurids on the basis of both photographic observations with small-meteor cameras and cameras with long focal length using the method of instantaneous exposure (τ exp = 5.6 × 10 −4 s). The study was carried out by constructing the theoretical meteor light curve while taking into account its fragmentation into two or more pieces and analyzing the aerodynamic pressure on the meteoroid at the point of splitting. The bulk densities of Taurids were obtained from an analysis of the observed light curves and compared with the strength categories obtained on the basis the data of the aerodynamic pressure at the point of meteoroid splitting. Comparing the resulting values with the known strength properties of various materials lets us conclude that Taurids could be considered structurally fragile bodies that fall into the a-strength category, have a density of 2.3 to 2.8 g/cm 3 , and can be characterized as carbonaceous chondrites. We discovered a connection between observed low-frequency pulsations of brightness of the splitting Taurids and the flares of individual pieces. We suggested that the observed lateral displacement velocity of the pieces could be caused by the explosive nature of the process of Taurid meteoroid fragmentation.
Abstract. Among 11 bright Geminid meteors photographed at the Institute of Astrophysics, Tajik Academy of Sciences (Dushanbe, Tajikistan), 3 displayed distinct high-frequency (more than 100 Hz) pulsations of brightness, or flickering. As a rule, for these Geminids, pulsations of brightness begin at the middle of their photographed path, at the height of about 75 km, and last until the end of the visible trajectory. Different possible meteoroid ablation mechanisms causing the flickering of the bright Geminids are discussed. The obtained results allow us to conclude that the observed high-frequency flickering of Geminid fireballs may be explained by an autofluctuating mechanism of the meteoroid ablation, i.e. by melting and cyclic ablation of the surface-layer of meteoric matter with the period corresponding to the observed period of the flickering.
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