Atomic-Scale Simulations of Meteor Ablation

Guttormsen, G.; Fletcher, Alex; Oppenheim, M. M.

doi:10.1002/essoar.10503451.1

Cited by 2 publications

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“…Kokonaisvaltainen asenne kumpuaa näkemyksestä, että arkeologia ei ole vain kenttätöitä eli kaivauksia ja inventointia, vaan ratkaisevan tärkeää on myös tieteenalan kyky yleisö-ja yhteistyöhön sekä toimintaan kaupunkisuunnittelun kanssa (esim. Lamb, 2008;Guttormsen, 2020).…”

Section: Johdantounclassified

Urbaani kulttuuriperintö ja fragmentaatioteoria: Esimerkkinä Turun kaupunkiarkeologia

Immonen

2023

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Despite the shift from a monument- or object-centred to a landscape-centred approach in the protection and management of urban cultural heritage, the analysis of cultural heritage as individual objects is still relevant. Theories on material culture do not see objects in the way they were conceived in monument-centred conservation. A case in point is fragmentation theory. The article uses this theory to analyse the relationship between archaeology and the urban landscape in Turku. Although fragmentation theory has its roots in prehistoric archaeology, the article adapts it to the modern, urban setting. Archaeological fragments have a physical connection with the past, but they can also act as agents independent of their original objects. This creative potential of fragments should be further explored in urban heritage management.

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Section: Johdantounclassified

Urbaani kulttuuriperintö ja fragmentaatioteoria: Esimerkkinä Turun kaupunkiarkeologia

Immonen

2023

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“…As a meteoroid ablates in Earth's atmosphere, a plasma forms at altitudes from 80 to 130 km due to sputtering and thermal ablation upon high‐velocity collisions between the meteoroid and atmospheric molecules (Guttormsen et al., 2020; Popova et al., 2001). The high‐density plasma cap that surrounds the meteoroid reflects radio waves, producing the head echo radar signature.…”

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confidence: 99%

Meteor Head Echo Analyses From Concurrent Radar Observations at AMISR Resolute Bay, Jicamarca, and Millstone Hill

2022

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Researchers frequently use high-power large aperture (HPLA) incoherent scatter radar (ISR) instruments around the world to gather data about meteoroids entering Earth's atmosphere. HPLA radar instruments measure between hundreds and thousands of head echoes per hour, depending on factors including frequency, power, geographic location and beam direction, in addition to the observed meteor population, that influence head echo detectability. High detection rates enable the use of statistical methods for head echo populations. The observed head echoes often originate from particles that are tens of microns in diameter; larger than the particles that can be observed in situ via impact detectors (Baggaley et al., 2007), but smaller than those observed via optical methods (Brown et al., 2017;Campbell-Brown & Close, 2007). Furthermore, signal processing techniques can be leveraged to obtain extremely accurate measurements of meteor motion during atmospheric entry from radar data.As a meteoroid ablates in Earth's atmosphere, a plasma forms at altitudes from 80 to 130 km due to sputtering and thermal ablation upon high-velocity collisions between the meteoroid and atmospheric molecules (Guttormsen et al., 2020;Popova et al., 2001). The high-density plasma cap that surrounds the meteoroid reflects radio waves, producing the head echo radar signature. Head echoes are observable at any HPLA radar. As the plasma expands and undergoes collisions with the surrounding atmosphere, a Farley-Buneman gradient-drift instability may develop in the meteor trail and create a non-specular radar return (Oppenheim & Dimant, 2015;Oppenheim et al., 2000). Most trails occur at equatorial radars due to field-aligned-irregularity (FAI) scattering when the incident wave is perpendicular to the background magnetic field (L. P. Dyrud et al., 2005), although non-FAI scattering has also been observed at higher latitudes (Chau et al., 2014;Kozlovsky et al., 2020).As the meteoroid heats and ablates, differential ablation may occur where certain constituents thermalize before others. This can create variation in radar cross-section during head echo detection, and such variation at the Arecibo radar facility was demonstrated to match the results of an ablation model (L. Dyrud & Janches, 2008;Janches et al., 2009). The effect has been observed in the laboratory for submicron-scale particles (DeLuca et al., 2022). The process of differential ablation may cause the meteoroid to fragment during atmospheric entry. Fragmentation has been observed optically (Vida et al., 2021), and on radar instruments via polarization of the

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Atomic-Scale Simulations of Meteor Ablation

Cited by 2 publications

References 0 publications

Urbaani kulttuuriperintö ja fragmentaatioteoria: Esimerkkinä Turun kaupunkiarkeologia

Urbaani kulttuuriperintö ja fragmentaatioteoria: Esimerkkinä Turun kaupunkiarkeologia

Meteor Head Echo Analyses From Concurrent Radar Observations at AMISR Resolute Bay, Jicamarca, and Millstone Hill

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