Some features of Geminid meteoroid disintegration in the Earth's atmosphere

Abstract

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.

Fragmentation and densities of meteoroids

“…From photographic observations of meteors in Dushanbe, Tajikistan, on the basis of the light curves of meteors and taking into account the quasicontinuous fragmentation, we present below the results of determination of the bulk densities of meteoroids belonging to different streams. The results of the determination of atmospheric trajectories and orbital elements of meteors, whose light curves were used for the determination of the bulk densities of meteoroids, were published earlier by Babadzhanov (1963), Babadzhanov et al (1966Babadzhanov et al ( , 1969Babadzhanov et al ( , 1982Babadzhanov et al ( , 1998 and now are available at the IAU Meteor Data Center in Lund, Sweden (Lindblad 1994).…”

Orbit, emission spectrum, and photometric analysis of two flickering sporadic fireballs

“…On the other hand, the observed flickering amplitude at times t > 0.7 seconds cannot be explained on the basis of an increase in the rotation rate in the atmosphere, since this mechanism is not effective for large meteoroids. Thus, for instance, Geminid meteoroids gain rotation in the atmosphere when their initial mass is below 6 × 10 −7 g (Babadzhanov & Konovalova 2004). On the other hand, Fig.…”

“…It must also be mentioned that, in the long term, the so-called Yarkovsky-O'Keefe-RadzievskiiPaddack (YORP) effect can also significantly change the rotational state of meteoroids and small asteroids (Čapek & Vokrouhlický 2004). On the other hand, other authors proposed that the flickering phenomenon can occur when the pressure of saturated vapors of meteor material and the outer pressure regulate each other automatically (Babadzhanov & Konovalova 2004). This is, in fact, one of the main possible mechanisms for meteor flickering listed in (Oleak 1964) and presented as responsible for the autofluctuating character of the evaporation process.…”

“…For a density ρ m = 3.7 g cm −3 , the calculated diameter yields 47 ± 2 cm for the "Fuencaliente" meteoroid and 12.8 ± 1.5 cm for "Sevilla". Observational data show that both, sporadic bright fireballs (Getman 1993;Brown et al 1998;Beech 2001) but also bright bolides belonging to annual meteor showers such as the Geminids (Halliday 1963;Babadzhanov & Konovalova 2004) and the Taurids (Konovalova 2003) show quasi-periodic brightness variations during the flight in the Earth's atmosphere. The flickering frequencies reported in the literature vary from a few Hz (low-frequency flickering) to about 500 Hz (high-frequency flickering).…”

Rotation of cometary meteoroids

“…This phenomenon, which is called flickering, is sometimes interpreted as the result of rotation of an asymmetric meteoroid (e.g., Beech & Brown 2000;Beech 2001;Spurný & Borovička 2001;Beech et al 2003). The rotational origin of flickering has, however, been doubted, and other explanations, such as an autofluctuating mechanism or triboelectric effects, have been suggested (e.g., Babadzhanov & Konovalova 2004;Borovička 2006;Spurný & Ceplecha 2008;Spurný et al 2012). (ii) Periodic variations in velocity of the Lost City bolide were also interpreted as the result of a changing cross-section due to rotation (Ceplecha 1996;Ceplecha & Revelle 2005).…”