Large Meteoroids Research Articles

Geology of the Eastern Barberton Greenstone Belt, South Africa: Early Deformation and the Role of Large Meteor Impacts

The eastern Barberton Greenstone Belt (BGB) includes four stratigraphic and structural divisions: from northwest to southeast, the Mlumati, Manzimnyama, and Paulus Synclines and the Emlembe Belt. All are made up largely of sedimentary rocks of the Fig Tree Group separated by antiformal belts of sheared Onverwacht Group komatiitic rocks. Fig Tree rocks in the Mlumati and Manzimnyama Synclines are mostly chemically precipitated banded iron formation (BIF) and banded ferruginous chert (BFC) with a major siliciclastic unit, the Gelegela Grit, composed of quartz-poor (<5% monocrystalline quartz, Qm) volcaniclastic sandstone showing abundant ~3.445–3.455 Ga detrital zircons. The Paulus Syncline is dominated by shale containing in the upper half chert-clast conglomerate and sparse lithic sandstone (Qm<10%) but includes near the middle lenticular units up to unit 30 m thick of quartz-rich (Qm >50%) sandstone. The Emlembe Belt consists largely of chert-clast conglomerate and quartz-bearing (Qm = 10–50%) sandstone. The Paulus and Emlembe belts show detrital zircon age peaks at ~3.295–3.275 Ga and ~3.445–3.455 Ga. While exhibiting overall similar stratigraphic development and detrital zircon ages, Fig Tree rocks in these belts show contrasting compositions and sediment sources. They do not represent parts a single basin or fairway of sediment transport and deposition. Fig Tree siliciclastic rocks mark the first deformation, uplift, and erosion in the BGB. However, the thinness of Fig Tree strata, mostly less than 1000 m, and rapid facies changes argue that deformation involved local uplifts and small basins that accumulated thin sedimentary sequences. We suggest that early Fig Tree deformation is consistent with crustal disruption triggered by large meteor impacts, starting perhaps as early as ~3.277 Ga but certainly by ~3.260 Ga. The Fig Tree Group may record a cluster of impacts that fragmented and destabilized a long-lived crust followed during later or post-Fig Tree time by tectonic uplift and orogeny.

Feasibility of meteor surveying from a Venus orbiter

Meteor and bolide phenomena caused by the atmospheric ablation of incoming meteoroids are predicted to occur at the planet Venus. Their systematic observation would allow to measure and compare the sub-mm to m meteoroid flux at different locations in the solar system. Using a physical model of atmospheric ablation, we demonstrate that Venus meteors would be brighter, shorter-lived, and appear higher in the atmosphere than Earth meteors. To investigate the feasibility of meteor detection at Venus from an orbiter, we apply the SWARMS survey simulator tool to sets of plausible meteoroid population parameters, atmospheric models and instrument designs suited to the task, such as the Mini-EUSO camera operational on the ISS since 2019. We find that such instrumentation would detect meteors at Venus with a 1.5× to 2.5× higher rate than at Earth. The estimated Venus–Earth detection ratio remains insensitive to variations in the chosen observation orbit and detector characteristics, implying that a meteor survey from Venus orbit is feasible, though contingent on the availability of suitable algorithms and methods for efficient on-board processing and downlinking of the meteor data to Earth. We further show that a hypothetical camera onboard the upcoming EnVision mission to Venus similar to the ISS instrument should detect many times more meteors than needed for an initial characterisation of the large meteoroid population at 0.7 au from the Sun.

Determining the population of large meteoroids in major meteor showers

We have estimated the largest meteoroids present in major meteor showers from observations conducted between 2019-2022 by the Geostationary Lightning Mapper (GLM) instrument on the GOES-R satellites. Our integrated time area products for the Leonids, Perseids and eta Aquariids are of order 5 × 1010 km2 hours. We compute photometric masses for shower fireballs using the approach of Vojáček et al. (2022) to correct from narrow-band GLM luminosity to bolometric luminosity and apply the luminous efficiency relation of Ceplecha & McCrosky (1976) at high speeds. Between 2019 and 2022, the showers definitely observed by GLM were the Leonids, Perseids, and eta Aquariids, with probable detections of the Orionids and Taurids. We find the largest meteoroids to be of order 7 kg for the Leonids, 3 kg for the Perseids, and 3 kg for the eta Aquariids, corresponding to meteoroids of ≈0.2 m diameter. The Orionids and Taurids had maximum meteoroid masses of 4 kg and 150 kg respectively. The Leonids and eta Aquariids are well fit by a single power-law with differential mass exponent, s, of 2.08 ± 0.08 and 2.00 ± 0.09 over the mass range 10−7< m < 1 kg. All showers had maximum meteoroid masses compatible with Whipple gas-drag ejection, with the exception of the Perseids which have much larger meteoroids than expected a result also consistent with observations from ground based instruments. This may reflect preferential ejection in narrow jets or possibly some form of mantle erosion/release in the past for the parent comet, 109P/Swift-Tuttle.

Observations of the new meteor shower from comet 46P/Wirtanen

Context. A new meteor shower λ-Sculptorids produced by the comet 46P/Wirtanen was forecast for December 12, 2023. The predicted activity was highly uncertain, but generally considered to be low. Observations in Australia, New Zealand, and Oceania were solicited to help constrain the size distribution of meteoroids in the shower. Aims. This work aims to characterize the new meteor shower, by comparing the observed and predicted radiants and orbits, and to provide a calibration for future predictions. Methods. Global Meteor Network video cameras were used to observe the meteor shower. Multi-station observations were used to compute trajectories and orbits, while single-station observations were used to measure the flux profile. Results. A total of 23 λ-Sculptorid orbits have been measured. The shower peaked at a zenithal hourly rate (ZHR) of 0.65−0.20+0.24 meteors per hour at λ⊙ = 259.988° ±0.042°. Due to the low in-atmosphere speed of 15 km s−1, the mean mass of observed meteoroids was 0.5 g (∼10 mm diameter), an order of magnitude higher than predicted. The dynamical simulations of the meteoroid stream can only produce such large meteoroids arriving at Earth in 2023 with correct radiants when a very low meteoroid density of ∼100 kg m−3 is assumed. However, this assumption cannot reproduce the activity profile. It may be reproduced by considering higher density meteoroids in a larger ecliptic plane-crossing time window (ΔT = 20 days) and trails ejected prior to 1908, but then the observed radiant structure is not reproduced.

The Taurid Resonant Swarm at Mercury

ABSTRACT It has previously been suggested that ejection and vaporization of Hermean surface material by meteoroids from comet 2P/Encke causes a seasonal enhancement in Mercury’s Ca exosphere observed by the NASA MESSENGER spacecraft in 2011-2015. The ESA/JAXA BepiColoen mission, now routeute to Mercury, will likely provide the next set of observational tests of this hypothesis after it enters orbit in late 2025. Here we study the Taurid Swarm Complex (IAU Code: STS), a population of cm-sized or larger meteoroids from Encke’s comet that encounters the Earth every 3–7 yr. Through analysis of previous observations of the STS and many-particle numerical simulations, we study the circumstances of encounters between the STS and Mercury and find that, unlike the Earth where STS encounters is observed in some years but not others, each time the STS is at perihelion it encounters Mercury on three consecutive planetary orbits. We further predict that the STS will encounter this planet during the early stages of BepiColombo’s orbital mission. The temporal flux profile during each encounter will be broad and possibly double-peaked with total number fluence 0.4×–1.7× that of the sporadic fluence for &amp;gt;1 kg meteoroids on the sub-radiant hemisphere of the planet. The meteoroid arrival direction and sub-radiant point strongly depend on True Anomaly Angle, switching from mainly nightside to mainly dayside impacts as Mercury travels from orbital perihelion to aphelion. Our predictions may be used to create detailed models of exosphere generation by Encke stream meteoroids.

Hidden morphology of Shackleton Crater, lunar South Pole

The article's goal is the detailed description of geomorphologic structures on the floor and interior walls of Shackleton Crater and a reconstruction of their formation histories.A Digital Elevation Model (DEM) with 20 m grid was constructed for the area around the crater based on Lunar Orbiter Laser Altimeter (LOLA) data. The DEM was analysed for slope steepness, Maximal Catchment Area (MCA) and four curvatures: maximal (kmax), minimal (kmin), horizontal (kh) and vertical (kv). Using this extensive set of Morphometric Variables (MVs) for the first time for a detail lunar DEM revealed unknown structures in permanently shaded areas.The previously identified large elevated structures “A" and “C" are attributed to landslides. “A" is related to a relatively large meteoroid impact that produced a recognisable crater on the exterior slope of Shackleton. “C" is associated with a landslide scar affecting the rim of Shackleton Crater directly above it. Structure “B” is not related to landsliding, but without of additional high-resolution geophysical data, its origin remains unclear.The low number of small impact craters on the steep slopes and sediment fields indicates ongoing surface erosion due to migration of unconsolidated fine grains and their deposition downslope. The foot slope zone is characterised by multiple accumulations of debris flows in the form of thin strips, identified as local landforms with kh > 0. On the surface of elevated structures “A”, “B” and “C” the map of kh reveals tree-like structures – erosion forms previously unknown in lunar geomorphology. These structures are formed by branching spurs characterised by several orders. The spurs are located relatively perpendicularly to the altitude isolines.The thickest (up to 120 m) slope deposits form a relatively flat area between the elevated structure “B" and the crater wall. These deposits should be of the greatest interest for future investigations searching for buried volatiles mixed with slope deposits.

Identifying meteorite droppers among the population of bright ‘sporadic’ bolides imaged by the Spanish Meteor Network during the spring of 2022

ABSTRACTThe extraordinary weather conditions available between February and March 2022 over Spain have allowed us to analyse the brightest fireballs recorded by the monitoring stations of the Spanish Meteor Network (SPMN). We study the atmospheric flight of 15 large meteoroids to determine if they are meteorite dropper events to prepare campaigns to search for freshly fallen extraterrestrial material. We investigate their origins in the Solar system and their dynamic association with parent bodies and meteoroid streams. Employing our python pipeline 3d-firetoc, we reconstruct the atmospheric trajectory utilizing ground-based multistation observations and compute the heliocentric orbit. In addition, we apply an ablation model to estimate the initial and terminal mass of each event. Using a dissimilarity criterion and propagating backward in time, we check the connection of these meteoroids with known complexes and near-Earth objects. We also calculate if the orbits are compatible with recent meteoroid ejections. We find that ∼27 per cent of these fireballs are dynamically associated with minor meteoroid streams and exhibit physical properties of cometary bodies, as well as one associated with a near-Earth asteroid. We identify two meteorite-producing events; however, the on-site search was unsuccessful. By considering that these fireballs are mostly produced by cm-sized rocks that might be the fragmentation product of much larger meteoroids, our findings emphasize the idea that the population of near-Earth objects is a source of near-term impact hazards, existing large Earth-colliding meteoroids in the known complexes.

Multi-instrument observations of the Pajala fireball: Origin, characteristics, and atmospheric implications

Meteor observations provide information about Solar System constituents and their influx onto Earth, their interaction processes in the atmosphere, as well as the neutral dynamics of the upper atmosphere. This study presents optical, radar, and infrasound measurements of a daytime fireball that occurred on 4 December 2020 at 13:30 UTC over Northeast Sweden. The fireball was recorded with two video cameras, allowing a trajectory determination to be made. The orbital parameters are compatible with the Northern Taurid meteor shower. The dynamic mass estimate based on the optical trajectory was found to be 0.6–1.7 kg, but this estimate can greatly vary from the true entry mass significantly due to the assumptions made. The meteor trail plasma was observed with an ionosonde as a sporadic E-like ionogram trace that lasted for 30 min. Infrasound emissions were detected at two sites, having propagation times consistent with a source location at an altitude of 80–90 km. Two VHF specular meteor radars observed a 6 minute long non-specular range spread trail echo as well as a faint head echo. Combined interferometric range-Doppler analysis of the meteor trail echoes at the two radars, allowed estimation of the mesospheric horizontal wind altitude profile, as well as tracking of the gradual deformation of the trail over time due to a prevailing neutral wind shear. This combined analysis indicates that the radar measurements of long-lived non-specular range-spread meteor trails produced by larger meteoroids can be used to measure the meteor radiant by observing the line traveled by the meteor. Furthermore, a multistatic meteor radar observation of these types of events can be used to estimate mesospheric neutral wind altitude profiles.

On mean motion resonances in the Geminid meteoroid stream

Analysing numerical models of the Geminid meteoroid stream for particle masses 0.00003–0.3 ​g we found evidence of several mean motion resonances: 1:2, 2:5, 3:7, 3:8 and 4:9 with Venus, 2:3 and 5:7 with the Earth and 7:1 with Jupiter. The resonant particles form dust trails located far from the Earth's orbit. Indeed, there is no observational support for resonant effects in the observed Geminid meteor shower. The trails are stable and compact, and consist of large (0.003–0.3 ​g) meteoroids.

Taurid Stream #628: A Reservoir of Large Cometary Impactors

Abstract The Desert Fireball Network observed a significant outburst of fireballs belonging to the Southern Taurid Complex of meteor showers between 2015 October 27 and November 17. At the same time, the Cameras for Allsky Meteor Surveillance project detected a distinct population of smaller meteors belonging to the irregular IAU shower #628, the s-Taurids. While this returning outburst was predicted and observed in previous work, the reason for this stream is not yet understood. 2015 was the first year that the stream was precisely observed, providing an opportunity to better understand its nature. We analyze the orbital elements of stream members and establish a size–frequency distribution from millimeter to meter size range. The stream is highly stratified with a large change of entry speed along Earth’s orbit. We confirm that the meteoroids have orbital periods near the 7:2 mean motion resonance with Jupiter. The mass distribution of this population is dominated by larger meteoroids, unlike that for the regular Southern Taurid shower. The distribution index is consistent with a gentle collisional fragmentation of weak material. A population of meter-sized objects is identified from satellite observations at a rate consistent with a continuation of the size–frequency distribution established at centimeter size. The observed change of longitude of perihelion among the s-Taurids points to recent (a few centuries ago) activity from fragmentation involving surviving asteroid 2015 TX24. This supports a model for the Taurid Complex showers that involves an ongoing fragmentation cascade of comet 2P/Encke siblings following a breakup some 20,000 yr ago.

Long-Living Meteoroids Formed during Radial Expansion of Large Meteoroids

Long-Living Meteoroids Formed during Radial Expansion of Large Meteoroids

Infrasound signals of fireballs detected by the Geostationary Lightning Mapper

Context. Fireballs are particularly bright meteors produced by large meteoroids or small asteroids that enter the Earth’s atmosphere. These objects, of sizes from some tens of centimetres to a few metres, are difficult to record with typical meteor detection methods. Therefore, their characteristics and fluxes are still not well known. Infrasound signals can travel particularly well through the atmosphere over large distances. Impacting meteoroids and asteroids can produce those signals, as well as space-detectable optical signatures. Aims. This paper aims to study and compare fireball data from the Geostationary Lightning Mappers (GLMs) on board the two Geostationary Observational Environmental Satellites (GOES-16 and GOES-17) and the data from the infrasound stations of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organisation (Vienna, Austria). The overall goal is a more accurate energy estimation of meteoroids and asteroids as well as a better understanding of both methods. Methods. The data consist of the brightest 50 events in the GLM database, as identified by recorded peak energy. For 24 of those fireballs, a significant signature could be identified in infrasound data. The data are supplemented by, if available, optical fireball data based on US government sensors on satellites provided by NASA’s Center for Near-Earth Object Studies (CNEOS). Results. The energies as computed from the GLM data range from 3.17 × 107 J up to 1.32 × 1012 J with a mean of 1.65 × 1011 J. The smallest meteoroid recorded by infrasound had an energy of about 1.8 × 109 J, the largest one of about 9.6 × 1013 J, and the mean energy is 5.2 × 1012 J. For 19 events, data were simultaneously available from all three data sources. A comparison between the energy values for the same event as determined from the different data sources indicates that CNEOS tends to give the lowest energy estimations. Analysis of infrasound data results in the largest derived energies. Conclusions. The energies derived using the three methods often deviate from one another by as much as an order of magnitude. This indicates a potential observational bias and highlights uncertainties in fireball energy estimation. By determining the fireball energy with another independent method, this study can help to better quantify and address this range of uncertainty.

атухание низкочастотных электромагнитных волн в нижней ионосфере земли под влиянием сильного локального возмущения в атмосфере.

The value and duration of attenuation of low frequency waves (1...10 kHz) in the presence of a strong local disturbance of the atmosphere have been estimated. Sources of significant local disturbances of the atmosphere are, for example, precipitation of energetic particles of radiation belts; electromagnetic pulses of lightning discharges; radiation of powerful low-frequency ground-based transmitters; invasion of large meteors. Strong local disturbances lead to an increase of ionization (concentration of free electrons) of the environment by several orders of magnitude in the region of space whose characteristic dimensions are comparable to the length of the wave (tens and hundreds of kilometers). As such a disturbance, we use the previously developed macroscopic model of an instantaneous, point release of a relatively large amount of energy in the atmosphere below the ionosphere. This model makes it possible to estimate the features of the propagation of low-frequency waves through the disturbed layer of the lower ionosphere by changing only two initial parameters: the disturbance energy and its initial height. It is shown that the attenuation value is almost independent of frequency and geo- and heliophysical conditions. For initial heights up to 50 km, the fading duration does not exceed ~ 2 min. With an increase of the initial altitude, the attenuation in the lower ionosphere becomes extremely large. However, for heights of 50 ... 70 km (depending on the value of energy), the horizontal size of the disturbance decreases significantly, which leads to a decrease in the fading time to tens of seconds for initial heights of more than 80 km.

A dynamical analysis of the Taurid Complex: evidence for past orbital convergences

ABSTRACT The goal of this work is to determine if the dynamics of individual Taurid Complex (TC) objects are consistent with the formation of the complex via fragmentation of a larger body, or if the current orbital affinities between the TC members result from other dynamical processes. To this end, the orbital similarity through the time of comet 2P/Encke, 51 near-Earth asteroids (NEAs), and 16 Taurid fireballs was explored. Clones of each body were numerically simulated backwards in time, and epochs when significant fractions of the clones of any two bodies approached each other with both a low Minimum Orbit Intersection Distance and small relative velocity were identified. Only 12 pairs of bodies in our sample show such an association in the past 20 000 yr, primarily circa 3200 BCE. These include 2P/Encke and NEAs 2004 TG10, 2005 TF50, 2005 UR, 2015 TX24, and several Southern Taurid fireballs. We find this orbital convergence to be compatible with the fragmentation of a large parent body 5000–6000 yr ago, resulting in the separation of 2P/Encke and several NEAs associated with the TC, as well as some larger meteoroids now recorded in the Taurid stream. However, the influence of purely dynamical processes may offer an alternative explanation for this orbital rapprochement without requiring a common origin between these objects. In order to discriminate between these two hypotheses, future spectral surveys of the TC asteroids are required.

Occurrence and Altitude of the Long‐Lived Nonspecular Meteor Trails During Meteor Showers at High Latitudes

AbstractMeteoroids entering the Earth's atmosphere produce ionized trails, which are detectable by radio sounding. Cylindrical underdense (and partly overdense) trails form a great majority of meteor echoes received by meteor radars (MRs). Additionally, the long‐lived nonspecular (LLNS) meteor echoes are received from irregularities of ionization generated along tracks of relatively large meteoroids. At high latitudes where the magnetic field is nearly perpendicular to the Earth's surface the LLNS echoes are possible only from non‐field‐aligned irregularities. The occurrence and height distributions of LLNS echoes are studied using MR observations at the high‐latitude Sodankylä Geophysical Observatory (SGO, 67°22′N, 26°38′E, Finland) during 2008–2019. Two parameters are analyzed: the percentage and height distribution of LLNS echoes. These LLNS echoes constitute about 3% of all MR detections. However, during certain meteor showers (i.e., the Geminids, Perseids, Quadrantids, Arietids or/and Daytime ζ‐Perseids, and Lyrids) the percentage of LLNS echoes is noticeably higher (about 10%, 8%, 7%, 7%, and 4%, respectively). Typically, the LLNSs occur ∼1–2 km higher than other echoes (in June–July the height difference is reduced to ∼0.5–1 km). Moreover, during the Lyrids, η‐Aquariids, Perseids, Orionids, and Leonids the LLNS echoes occur noticeably, up to 3–5 km, higher than the echoes from other types of trails.

Two Strengths of Ordinary Chondritic Meteoroids as Derived from Their Atmospheric Fragmentation Modeling

Abstract The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth’s atmosphere can explore meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that the meteoroid’s strength is significantly lower than that of the recovered meteorites. We present a 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 observations were made by the autonomous observatories of the European Fireball Network and include detailed radiometric light curves. A model, called the semiempirical fragmentation model, was developed to fit the light curves and decelerations. Videos showing individual fragments were available in some cases. The results demonstrated that meteoroids do not fragment randomly but in two distinct phases. The first phase typically corresponds to low strengths of 0.04–0.12 MPa. In two-thirds of cases, the first phase was catastrophic or nearly catastrophic with at least 40% of mass lost. The second phase corresponds to 0.9–5 MPa for confirmed meteorite falls and somewhat lower strengths, from about 0.5 MPa, for smaller meteoroids. All of these strengths are lower than the tensile strengths of ordinary chondritic meteorites cited in the literature, 20–40 MPa. We interpret the second phase as being due to cracks in meteoroids and the first phase as a separation of weakly cemented fragments, which reaccumulated at the surfaces of asteroids after asteroid collisions.

Formation of Microspherules of Lunar Regolith in Plasma–Dust Processes Initiated by Meteoroid Impacts

The possibility of the formation of microspherules in plasma-dust processes initiated by meteoroids impacting the lunar surface is discussed. It is demonstrated that spherules are formed from the material of the melt zone created by a high-speed meteoroid impacting the lunar surface. Initially, they rise above the surface of the Moon and then fall back. It is these spherules that were found in the course of investigation of the lunar soil. Liquid spherules solidify while floating above the surface of the Moon and acquire electric charges as a result of the interaction with electrons and ions, together with the solar radiation, thereby becoming part of the plasma-dust system above the Moon. The concentration of spherules in dusty plasma above the lunar surface and their size distribution are obtained. The upper bound of the spherule size in the distribution is determined by the existence of the upper bound in the statistical data on the size of relatively small meteoroids and amounts to several micrometers. The size of spherules substantially larger than 1 μm corresponds to meteoroids larger than 1 cm. It is impossible to obtain unique statistics with respect to size for large meteoroids. Therefore, it is possible to obtain the size distribution only of spherules of micron and submicron size. The size of meteoroids impacting the lunar surface and creating relatively large spherules can only be estimated. It is demonstrated that the presence of spherules in dusty plasma above the lunar surface can be discovered by piezoelectric sensors during future Luna-25 and Luna-27 missions.

Geomagnetic Variations Caused by the Lipetsk Meteoroid’s Passage and Explosion: Measurement Results

The magnetic effect of meteors was first observed and theoretically explained back in the middle of the 20th century. The mechanisms for the magnetic effect of large celestial bodies (1–10 m and more) fundamentally differ from the mechanisms of geomagnetic field disturbances caused by meteors at ionospheric heights. The passage of a large meteoroid through the atmosphere and its explosion are accompanied by the generation of a powerful shock wave and the formation of a plume, which result in a geomagnetic effect. To the present day, researchers are divided on the main mechanism for the geomagnetic effect of large meteoroids. The Tunguska and Chelyabinsk meteoroid measurements are available for studies. In the case of the Chelyabinsk meteoroid, the variations in the geomagnetic field are detected and explained both prior to and after the explosion of this celestial body. Analyzing observations of the passage of any large enough celestial body is of considerable theoretical and practical interest. The purposes of this study are to present the analysis of magnetic field variations that arose as a result of the Lipetsk meteoroid passage through the Earth’s magnetosphere and atmosphere and to estimate and discuss the magnetic effect and its mechanisms. The fall rate of such meteoroids is 0.68 yr–1. Using the data provided by the Magnetic Observatory of Karazin Kharkiv National University (Kharkiv, Ukraine), the temporal variations in the horizontal components of the geomagnetic field on June 21, 2018, (the day of the Lipetsk meteoroid passage) and on June 20 and 22, 2018, (the reference days) have been analyzed. The meteoroid’s initial speed was 14.4 km/s, the initial mass was 113 t, and the initial size equaled approximately 4 m. The distance from the observatories to the site where the meteoroid explosion-like release of energy occurred was 360 km. The passage of the Lipetsk meteoroid in the magnetosphere and atmosphere has been shown to be accompanied by alternating variations in the geomagnetic field components. The magnetic effect of the magnetosphere was observed 54–56 min before the meteoroid explosion; the amplitude of the disturbance in the geomagnetic field did not exceed 0.5–1 nT, and the duration was 15–20 min. Alternating spikes (first positive, then negative) in the H and D component level were observed after the meteoroid explosion with a ∼6-min delay. The spike amplitude was ∼1.2–1.5 nT, while the duration of the magnetic effect from the ionosphere reached tens of minutes. The models for the magnetic effects observed are suggested and theoretical estimates are performed. The observations and the estimates are in good agreement.

Global Monitoring and Characterization of Infrasound Signatures by Large Fireballs

Large meteoroids can be registered in infrasound recordings during their entry into the Earth’s atmosphere. A comprehensive study of 10 large fireball events of the years 2018 and 2019 highlights their detection and characterization using global infrasound arrays of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The study focuses on the observation and event analysis of the fireballs to estimate their respective location, yield, trajectory, and entry behavior. Signal characteristics are derived by applying the Progressive Multi-Channel Correlation method as an array technique. The comparison of the events with a NASA reference database as well as the application of atmospheric propagation modeling allows to draw conclusions about infrasound-based detection capability, localization accuracy, yield estimation, and source characterization. The infrasound technique provides a time- and location-independent remote monitoring opportunity of impacting near-Earth objects (NEOs), either independent or complementary to other fireball observation methods. Additionally, insights about the detection and localization capability of IMS infrasound stations can be gained from using large fireballs as reference events, being of importance for the continuous monitoring and verification of atmospheric explosions in a CTBT context.

Radiation phenomenon for large meteoroids

Aims. The relationship between the intrinsic properties of a large meteoroid, that is, mass, density, chemical composition, and flight velocity, and its spectrum are identified. Methods. Assuming thermochemical equilibrium and inviscid flow and using a quasi-one-dimensional approach, the flow-field and radiative transfer problems are solved from the ablating wall of a meteoroid to the observer on the ground. Results. The study discovers that the precursor region immediately ahead of the shock layer absorbs nitrogen and oxygen lines, and thereby modifies the spectrum received by the ground observer. The study leads to a computer code with which the observed spectra and light-curves for Benesov and Sumava meteoroids are numerically and approximately reproduced with the help of a meteoroid fragmentation theory. Luminous efficiency value is obtained as a byproduct.