V. P. Stulov

Extra-atmospheric masses of the Canadian Network bolides

The extra-atmospheric masses of meteoric bodies have previously been determined using the so-called photometric formula, by integrating the luminosity along the visible portion of the trajectory. On the other hand, the mass of a meteoroid characterizes the braking height and intensity of the meteoroid in the atmosphere. Some studies note a substantial disagreement between the masses obtained in these two ways, using bolides of the European Bolide Network and of the US Prairie Network as examples. In nearly all cases, the photometric mass exceeds the mass determined from the braking intensity by an order of magnitude or more. Two explanations were suggested for this fact. According to one of them, a swarm of fragments, similar in size, rather than a single body is moving. This swarm brakes as an individual fragment, while it glows as a collection of fragments; i.e., it is much brighter than an individual fragment. The extra-atmospheric mass is determined here by properly fitting the parameters describing the braking of the meteor along the entire visible section of the trajectory. The results obtained for the bolides of the Canadian Network confirm again that the photometric approach is not tenable.

Consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface

AbstactPossible consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface are described. The methodological basis of classification of consequences is the solution of meteor physics equations characterizing the trajectory of a body in the atmosphere, namely, the dependence of the body’s velocity and mass on the flight altitude. The solution depends on two dimensionless parameters characterizing the drag altitude and the role of mass loss by a meteoroid during its motion in the atmosphere. Depending on values of these parameters, the degree of effect on the planetary surface considerably changes. In particular, the conditions of cratering and meteorite fall on the planetary surface are obtained. The results are presented in a simple analytical form. They quite match to the real events considered in the paper. Recommendations are given on further investigations into the important problem of interaction of cosmic bodies with planetary atmospheres.

Determining the Parameters of Fragmenting Meteoroids from Their Braking in the Atmosphere

The ballistic coefficients and ablation parameters of Prairie Network (United States) fireballs are determined by the best fitting in “velocity–height” variables. The braking trajectories based on the model of successive destruction with ablation are used as the test functions. The fitting accuracy of the observed trajectory was found to be approximately the same for the model of successive destruction and for the model of motion of a single body. At least, the fitting accuracy allows us neither to confirm nor to reject the fragmentation of meteoroids within the luminous segment of the trajectory. The previously noted excess of the observed luminosity of the fireballs studied here (Popova, 1997) over the value calculated for the dynamical mass, which was estimated from the model of a single body (Kulakov and Stulov, 1992), can be explained by deviations of the meteoroid shapes from a sphere.

Drag coefficients for bodies of meteorite-like shapes

The drag coefficients and the patterns of supersonic flows around rectangular parallelepipeds (bodies with rectangular and square faces-bricks and tiles, respectively) were found from numerical experiments. These drag coefficients cx are considerably different from the values used, in particular, in the meteor-related literature to calculate the motion of brick-shaped meteor bodies. The values of cx and the flow pattern near the face of the body weakly depend on the relative size of the body within the parameter range considered.

Standards for crater formation and meteorite fallout by the light sector of an atmospheric trajectory

New application of the simple solution of meteor physics equations, which depends on two dimension� less parameters, the ballistic coefficient α and the massloss parameter β, is given in the paper. The solu� tion allows easily predicting important consequences of the entry of meteor bodies into the atmosphere and of their interaction with the surface of the planet. The matter concerns the forecast of the crater formation and meteorite fallout on the basis of observable prop� erties of the light sector of the atmospheric trajectory of the bolide. The problem of the approximation of the observed motion of the bolide in the atmosphere is reduced to the search for such values of parameters α and β at which the analytical solution of meteor physics equa� tions

A model of the motion of the nneuschwanstein bolide in the atmosphere

A new model of the atmospheric entry of the Neuschwanstein fireball has been developed. The fireball was photographed in Germany on April 6, 2002, and three fragments of it were found during a subsequent search in the territory predicted according to observations. In this study, the form of the meteoric body is assumed to be a cube with rounded vertices and edges. The estimated mass of the meteoric body at its entry into the atmosphere is close to the literature data obtained using seismic, acoustic, and infrasonic analysis. It is noted that the analysis of this fireball was for the first time made without using the photometric approach.

Entry Mass for Bolides of the Canadian Network

Previously, the mass of meteor bodies was determined according to the so-called photometric formula by integration of the luminosity along the visible segment of the trajectory. On the other hand, the altitude and the meteor aerobraking rate in the atmosphere depend on the mass of the meteor body. In a number of papers, it was noted that the bolide masses estimated by the two indicated methods significantly differ from each other. For example, according to these data related to the bolides of both the European network and the US Prairie network, the photometric mass exceeds by an order of magnitude or more the mass determined by the aerobraking rate. In this study, we estimate the extraatmospheric meteor mass by choosing parameters that characterize the meteor aerobraking along the entire visible segment of the trajectory. The results for bolides of the Canadian network confirm once again the inadequacy of the photometric approach. In processing the observed-data, we widely exploit the conception of the photometric mass of a meteor body

Comparative Analysis of Models for Disintegration of Meteoric Bodies

A model for fast sequential disintegration of meteoroids in the terrestrial atmosphere, which takes a scale factor into account, was published by Ivanov and Ryzhanskii (1997). The trajectory of a nonablating body was determined by stage-by-stage computations; the number of stages could be more than 30. In the present study, this physical model is represented by a set of differential equations, which are solved by the method of separation of variables, in particular, with allowance for ablation. For bounded values of the mass-loss parameter, the solution is expressed in terms of elementary functions. Examples of the calculation of meteoric-body trajectories based on other models and their comparison with the proposed model are presented. Comparison of the results indicate the efficiency of these models in solving the inverse problems of dynamics and disruption of meteoroids in the atmosphere.

The extra-atmospheric mass of small meteoroids of the Prairie and Canada bolide camera networks

The existing methods for determining the extra-atmospheric mass of meteor bodies from observations of their movement in the atmosphere allow a certain arbitrariness. Active attempts to overcome the discrepancy between the results of calculations based on different approaches often lead to physically incorrect conclusions. A way out is to laboriously accumulate the estimates and computation results and to consistently remove ambiguities. To correctly interpret the observed brightness of a meteor, one should use contemporary methods and the results of physical studies of the emitting gas. In the present work, the extra-atmospheric masses of small meteoroids of the Prairie and Canada bolide camera networks were calculated from the observed braking. It turned out that, in many cases, the conditions of movement of meteor bodies in the atmosphere corresponded to a free molecular airflow about a body. The so-called dynamic mass of the bodies was estimated from the real densities of the meteoroid material, which corresponded to monolithic water ice and stone, and for the proper values of the product of the drag coefficient and shape factor. When producing the trial function for the body trajectories in the “velocity-altitude” variables, we did not allow for fragmentation explicitly, since it is less probable for small meteoroids than for large ones. As before, our estimates differ substantially from the photometric masses published in the corresponding tables.

Large fireballs: Evaporation and fragmentation

The main physical processes during the entry of natural 0.01-to 100-m large cosmic bodies into planetary atmospheres are fragmentation and evaporation. The relative role of evaporation can be characterized by the mass-loss parameter, which is proportional to the ratio of the kinetic energy per unit mass of the body to the effective enthalpy of evaporation. Examples of actual large fireballs are given for various values of this parameter. The proposed general approach helps in understanding the extensive observational data of various level of reliability and also makes it possible to preliminarily separate real hypotheses from unrealistic ones.