Many existing optical meteor trajectory estimation methods use the approximation that the velocity of the meteor at the beginning of its luminous phase is equivalent to its velocity before atmospheric entry. Meteoroid kinetic energy loss prior to the luminous phase cannot be measured, but for some masses and entry geometries neglecting this loss may lead to non-negligible deceleration prior to thermal ablation. Using a numerical meteoroid ablation model, we simulate the kinematics of meteoroids beginning at 180 km with initial velocities ranging from 11 km/s to 71 km/s, and compare model velocities at the moment of detection to measurements. We validate the simulations by comparing the simulated luminous beginning heights with observed beginning heights of different populations of meteors detected with different optical systems. We find that most low-velocity meteoroids have a significant velocity difference of 100 m/s to 750 m/s (depending on meteoroid type, mass, and observation system). This systematic underestimate of meteoroid speeds also results in systematically lower semi-major axes for meteoroid orbits.
We follow our previous work about the September epsilon Perseid (SPE) meteoroid cluster from 2016. We assumed that the mass-dominated meteoroid is the parent body of the cluster and that the observed positions of meteoroids are controlled by the ejection velocities and the action of solar radiation pressure. A formula for the dependence of meteoroid ejection velocities on the mutual positions, masses, and cluster age was derived. Knowing values and directions of ejection velocities together with meteoroid masses then allowed us to determine the most likely process of cluster formation. The met…
In February 15 2013 a medium-sized meteoroid impacted the atmosphere in the region of Chelyabinsk, Russia. After its entrance to the atmosphere and after travel by several hun- dred of kilometers the body exploded in a powerful event responsible for physical damages and injured people spread over a region enclosing several large cities. We present in this letter the results of a preliminary reconstruction of the orbit of the Chelyabinsk meteoroid. Using evidence gathered by one camera at the Revolution Square in the city of Chelyabinsk and other videos recorded by witnesses in the close city o…
Meteoroids impacting the Earth on a daily basis are fragments of asteroids and comets. By studying fireballs produced during their disintegration in the atmosphere, we can gain information about their source regions and the properties of their parent bodies. In this work, data on 824 fireballs presented in an accompanying paper and catalog are used. We propose a new empirical parameter for the classification of the physical properties of meteoroids, based on the maximum dynamic pressure suffered by the meteoroid in the atmosphere. We then compare the physical and orbital properties of meteoroi…
The physical composition and structure of meteoroids gives us insight into the formation processes of their parent asteroids and comets. The strength of and fundamental grain sizes in meteoroids tell us about the environment in which small solar system bodies formed, and the processes which built up these basic planetary building blocks. The structure of meteorites can be studied directly, but the set of objects which survive entry through the atmosphere is biased toward large, strong objects with slow encounter speeds. Fragile objects, small objects and objects with high relative speeds are v…
Shock waves and the associated phenomena generated by strongly ablating meteoroids with sizes greater than a few millimeters in the lower transitional flow regime of the Earth's atmosphere are the least explored aspect of meteor science. In this paper, we present a comprehensive review of literature covering meteor generated shock wave phenomena, from the aspect of both meteor science and hypersonic gas dynamics. The primary emphasis of this review is placed on the mechanisms and dynamics of the meteor shock waves. We discuss key aspects of both shock generation and propagation, including the …
We analyze the activity of the Northern ω-Scorpiid meteor shower between 2010 and 2012. For this purpose we have employed an array of low-lux CCD video cameras and spectrographs deployed at different astronomical observatories in Spain. As a result of our survey, the atmospheric trajectory and radiant position of 11 of these meteor events were obtained. The tensile strength and orbital parameters of the progenitor meteoroids have been also calculated. The calculated orbital data and the behaviour of these meteoroids in the atmosphere are compatible with an asteroidal origin of this stream. In …
Meteoroids impacting the Earth atmosphere are commonly classified using the PE criterion. This criterion was introduced to support the identification of the fireball type by empirically linking its orbital origin and composition characteristics. Additionally, it is used as an indicator of the meteoroid tensile strength and its ability to penetrate the atmosphere. However, the level of classification accuracy of the PE criterion depends on the ability to constrain the value of the input data, retrieved from the fireball observation, required to derive the PE value. To overcome these uncertainti…
A meteoroid's hypersonic passage through the Earth's atmosphere results in ablational and fragmentational mass loss. Potential shock waves associated with a parent object as well as its fragments can modify the surrounding atmosphere and produce a range of physico-chemical effects. Some of the thermally driven chemical and physical processes induced by meteoroid-fragment generated shock waves, such as nitric oxide (NO) production, are less understood. Any estimates of meteoric NO production depend not only on a quantifiable meteoroid population and a rate of fragmentation, with a size capable …
Multi-Arrival Infrasound from Meteoroids: Fragmentation Signatures versus Propagation Effects in a Fine-Scale Layered Atmosphere
Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences（俄罗斯科学院奥布霍夫大气物理研究所）；Sandia National Laboratories（桑迪亚国家实验室）；Western University（韦仕敦大学）；Moscow State University（莫斯科国立大学）
Meteoroids are pieces of asteroids and comets. They serve as unique probes to the physical and chemical properties of their parent bodies. We can derive some of these properties when meteoroids collide with the atmosphere of Earth and become a meteor or a bolide. Even more information can be obtained when meteoroids are mechanically strong and slow enough to drop meteorites. Through physical modeling of bright meteors, we describe their fragmentation in the atmosphere. We also derive their mechanical strength and the mass distribution of the fragments, some of which may hit the ground as meteo…
The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth's atmosphere can prospect meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that meteoroid strength is significantly lower than that of the recovered meteorites. We present detailed study of atmospheric fragmentation of seven meteorite falls, all ordinary chondrites, and 14 other fireballs, where meteorite fall was predicted but the meteorites, probably also ordinary chondrites, were not recovered. All obse…
Despite ablation and drag processes associated with atmospheric entry of meteoroids were a subject of intensive study over the last century, little attention was devoted to interpret the observed fireball terminal height. This is a key parameter because it not only depends on the initial mass, but also on the bulk physical properties of the meteoroids and hence of their ability to ablate in the atmosphere. In this work we have developed a new approach that is tested using the fireball terminal heights observed by the Meteorite Observation and Recovery Project operated in Canada between 1970-19…
Fireball networks establish the trajectories of meteoritic material passing through Earth's atmosphere, from which they can derive pre-entry orbits. Triangulated atmospheric trajectory data requires different orbit determination methods to those applied to observational data beyond the Earth's sphere-of-influence, such as telescopic observations of asteroids. Currently, the vast majority of fireball networks determine and publish orbital data using an analytical approach, with little flexibility to include orbital perturbations. Here we present a novel numerical technique for determining meteo…
X-ray microtomography (XMT), X-ray diffraction (XRD) and magnetic hysteresis measurements were used to determine micrometeorite internal structure, mineralogy, crystallography, and physical properties at ~μm resolution. The study samples include unmelted, partially melted (scoriaceous) and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types, but also reveals changes in meteoroid properties during atmospheric entry at various velocities. At low entry velocities, meteoroids do not melt, a…
On 10 June 2012, an Earth-grazer meteor which lasted over 17 s with an absolute magnitude of -4.0 $\pm$ 0.5 was observed over Spain. This work focuses on the analysis of this rare event which is, to our knowledge, the faintest Earth-grazing meteor reported in the scientific literature, but also the first one belonging to a meteor shower. Thus, the orbital parameters show that the parent meteoroid belonged to the Daytime $ζ$-Perseid meteoroid stream. According to our calculations, the meteor was produced by a meteoroid with an initial mass ranging between 115 and 1.5 kg. During its encounter wi…
Infrasound monitoring has proved to be effective in detection of the meteor generated shock waves. When combined with optical observations of meteors, this technique is also reliable for detecting centimeter-sized meteoroids that usually ablate at high altitudes, thus offering relevant clues that open the exploration of the meteoroid flight regimes. Since a shock wave is formed as a result of a passage of the meteoroid through the atmosphere, the knowledge of the physical parameters of the surrounding gas around the meteoroid surface can be used to determine the meteor flow regime. This study …
A Geminid fireball with an absolute magnitude of -13 was observed over the south of Spain on Dec. 15, 2009. This extraordinarily bright event (the brightest Geminid ever recorded by our team) was imaged from two meteor observing stations operated by the SPanish Meteor Network (SPMN). The bolide exhibited fast and quasi-periodic variations in brightness, a behaviour typically associated to the rotation of the parent meteoroid. The inferred tensile strength of this particle was found to be significantly higher that the typical values obtained for Geminid meteoroids. The fireball penetrated in th…
In studies of the oldest solar system bodies - comets and asteroids - it is their fragments - meteoroids - that provide the most accessible planetary material for detailed laboratory analysis in the form of dust particles or meteorites. Some asteroids and comets were visited by spacecrafts and returned interplanetary samples to Earth, while missions Hayabusa 2 and OSIRIX-REx visiting asteroids Ryugu and Bennu are ongoing. However, the lack of representative samples of comets and asteroids opens the space to gain more knowledge from direct observations of meteoroids. At collision with the Earth…
Sungrazing comets have always captured a lot of interest and curiosity among the general public as well as scientists since ancient times. The perihelion passage of comet C/2012 S1 (ISON) at the end of this year (on 2013 November 28) is an eagerly awaited event. In this work, we do a mathematical study to check whether meteoroids ejected from this comet during its journey around the sun can produce spectacular meteor phenomena on Earth. Our calculations show that although the orbital elements of this comet are much more favourable than for most sungrazers to have its descending node near the E…
We use the Slovak and Czech video meteor observations, as well as video meteoroid orbits collected in the CAMS, SonotaCo, EDMOND and DMS catalogues, for an analysis of the distribution of meteoroid orbits within the stream of the Geminids and of the dispersion of their radiants. We concentrate on the influence of the measurement errors on the precision of the orbits obtained from the video networks that are based on various meteor-detection software packages and various meteor orbital element softwares. The observed orbital dispersions in the Geminid stream described by the median absolute dev…
We analyze the likely link between the recently discovered Near Earth Object 2012XJ112 and a bright fireball observed over the south of Spain on December 27, 2012. The bolide, with an absolute magnitude of -9 +- 1, was simultaneously imaged during the morning twilight from two meteor stations operated by the SPanish Meteor Network (SPMN). It was also observed by several casual witnesses. The emission spectrum produced during the ablation of the meteoroid in the atmosphere was also recorded. From its analysis the chemical nature of this particle was inferred. Although our orbital association so…
A ballistic reconstruction of a meteoroid orbit can be made if enough information is available about its trajectory inside the atmosphere. A few methods have been devised in the past and used in several cases to trace back the origin of small impactors. On February 15, 2013, a medium-sized meteoroid hit the atmosphere in the Chelyabinsk region of Russia, causing damage in several large cities. The incident, the largest registered since the Tunguska event, was witnessed by many thousands and recorded by hundreds of amateur and public video recording systems. The amount and quality of the inform…
The arrival of solid particles from outside our solar system would present us with an invaluable source of scientific information. Attempts to detect such interstellar particles among the meteors observed in Earth's atmosphere have almost exclusively assumed that those particles moving above the Solar System's escape speed -- particles on orbits hyperbolic with respect to the Sun-- were precisely the extrasolar particles being searched for. Here we show that hyperbolic particles can be generated entirely within the Solar System by gravitational scattering of interplanetary dust and meteoroids …
Meteor physics can provide new clues about the size, structure, and density of cometary disintegration products, establishing a bridge between different research fields. From meteor magnitude data we have estimated the mass distribution of meteoroids from different cometary streams by using the relation between the luminosity and the mass obtained by Verniani (1973). These mass distributions are in the range observed for dust particles released from comets 1P/Halley and 81P/Wild 2 as measured from spacecraft. From the derived mass distributions, we have integrated the incoming mass for the mos…
On October 8, 2011 the Earth crossed dust trails ejected from comet 21P/Giacobini-Zinner in the late 19th and early 20th 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…
We report high resolution multi-station observations of meteors by the Canadian Automated Meteor Observatory (CAMO) recorded from June 2009 to August 2010. Our survey has a limiting detection magnitude of +5 mag in R-band, equivalent to a limiting meteoroid mass of ~2*E-7 kg. The high metric trajectory accuracy (of the order of 30 m perpendicular to the solution and 200 m along-track) allows us to determine velocities with average uncertainty of < 1.5% in speed and ~0.4 degr in radiant direction. A total of 1739 meteors had measured orbits. The data has been searched for meteors in hyperbolic …
On 2008 October 7, small asteroid 2008 TC3 turned itself into the parent body of the first meteor ever to be predicted before entering the Earth's atmosphere. Over five years later, the 2014 AA event became the second instance of such an occurrence. The uncertainties associated with the pre-impact orbit of 2008 TC3 are relatively small because thousands of observations were made during the hours preceding the actual meteor airburst. In sharp contrast, 2014 AA was only observed seven times before impact and consequently its trajectory is somewhat uncertain. Here, we present a recalculation of t…
Context. The mirror tracking system of the Canadian Automated Meteor Observatory (CAMO) can track meteors in real time, providing an effective angular resolution of 1 arc second and a temporal resolution of 100 frames per second. Aims. We describe the upgraded hardware and give details of the data calibration and reduction pipeline. We investigate the influence of meteor morphology on radiant and velocity measurement precision, and use direct observations of meteoroid fragmentation to constrain their compressive strengths. Methods. On July 21, 2017, CAMO observed a ~4 second meteor on a JFC or…
Everyday thousands of meteoroids enter the Earth's atmosphere. The vast majority burn up harmlessly during the descent, but the larger objects survive, occasionally experiencing intense fragmentation events, and reach the ground. These events can pose a threat for a village or a small city; therefore, models of asteroid fragmentation, along with accurate post-breakup trajectory and strewn field estimation, are needed to enable a reliable risk assessment. In this work, a methodology to describe meteoroids entry, fragmentation, descent, and strewn field is presented by means of a continuum appro…
While steady empirical progress has been made in understanding the structure and composition of hot planet atmospheres, direct measurements of velocity signatures, including winds, rotation, and jets, have lagged behind. Quantifying atmospheric dynamics of hot planets is critical to a complete understanding of their atmospheres and such measurements may even illuminate other planetary properties, such as magnetic field strengths. In this manuscript we present the first detection of the Balmer lines H$α$ and H$β$ in the atmosphere of the ultra-hot Jupiter WASP-33 b. Using atmospheric models whi…
It has recently been shown by Egal et al. (2017) that some types of existing meteor in-atmosphere trajectory estimation methods may be less accurate than others, particularly when applied to high precision optical measurements. The comparative performance of trajectory solution methods has previously only been examined for a small number of cases. Besides the radiant, orbital accuracy depends on the estimation of pre-atmosphere velocities, which have both random and systematic biases. Thus it is critical to understand the uncertainty in velocity measurement inherent to each trajectory estimati…
The PANSY Meteor Head-echo Orbit Catalogue: Continuous Antarctic Radar Observations of Southern Meteoroid Streams
UiT The Arctic University of Norway（挪威北极大学）；Leibniz Institute of Atmospheric Physics at the University of Rostock（罗斯托克大学莱布尼茨大气物理研究所）；Research Institute for Sustainable Humanosphere, Kyoto University（京都大学可持续人类圈研究所）；National Institute of Polar Research（国立极地研究所）；Polar Science, Graduate Institute for Advanced Studies, SOKENDAI（日本综合研究大学院大学极地科学研究生院）；Swedish Institute of Space Physics（瑞典空间物理研究所）
Decameter-sized Earth Impactors -- II: A Bayesian Inference Approach to Meteoroid Ablation Modeling
Department of Physics and Astronomy, University of Western Ontario（韦仕敦大学物理与天文学系）；Western Institute for Earth and Space Exploration, University of Western Ontario（韦仕敦大学西部地球与空间探索研究所）
The initial results of a two year simultaneous optical-radar meteor campaign are described. Analysis of 105 double-station optical meteors having plane of sky intersection angles greater than 5 degrees and trail lengths in excess of 2 km also detected by the Middle Atmosphere Alomar Radar System (MAARSY) as head echoes was performed. These events show a median deviation in radiants between radar and optical determinations of 1.5 degrees, with 1/3 of events having radiant agreement to less than one degree. MAARSY tends to record average speeds roughly 0.5 km/s and 1.3 km higher than optical rec…
On October 8th, 2011 the Earth crossed the dust trails left by comet 21P/Giacobini-Zinner during its XIX and XX century perihelion approaches with the comet being close to perihelion. The geometric circumstances of that encounter were thus favorable to produce a meteor storm, but the trails were much older than in the 1933 and 1946 historical encounters. As a consequence the 2011 October Draconid display exhibited several activity peaks with Zenithal Hourly Rates of about 400 meteors per hour. In fact, if the display had been not forecasted, it could have passed almost unnoticed as was strongl…
In this paper we present three-dimensional atmospheric simulations of the hot Jupiter HD~189733b under two different scenarios: local chemical equilibrium and including advection of the chemistry by the resolved wind. Our model consistently couples the treatment of dynamics, radiative transfer and chemistry, completing the feedback cycle between these three important processes. The effect of wind--driven advection on the chemical composition is qualitatively similar to our previous results for the warmer atmosphere of HD~209458b, found using the same model. However, we find more significant al…
Cosmic collisions on planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On June 3, 2010 a bolide in Jupiter's atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths. The bolide appeared as a flash of 2 s duration in video recording data of the planet. The analysis of the light curve of the observations results in an estimated energy of the impact of 0.9-4.0x10^{15} J which corresponds to a colliding body of 8-13 m diameter assuming a mean density of 2 g cm^{-3}. Images …
On 5th December 2020 at 17:28 UTC, the Japan Aerospace Exploration Agency's Hayabusa-2 sample return capsule came back to the Earth. It re-entered the atmosphere over South Australia, visible for 53 seconds as a fireball from near the Northern Territory border toward Woomera where it landed in the the Woomera military test range. A scientific observation campaign was planned to observe the optical, seismo-acoustic, radio and high energy particle phenomena associated with the entry of an interplanetary object. A multi-institutional collaboration between Australian and Japanese universities resu…
Accurately measuring and modeling the Lyman-$α$ (Ly$α$; $λ$1215.67 Å) emission line from low mass stars is vital for our ability to build predictive high energy stellar spectra, yet interstellar medium (ISM) absorption of this line typically prevents model-measurement comparisons. Ly$α$ also controls the photodissociation of important molecules, like water and methane, in exoplanet atmospheres such that any photochemical models assessing potential biosignatures or atmospheric abundances require accurate Ly$α$ host star flux estimates. Recent observations of three early M and K stars (K3, M0, M…
