The ionization efficiency of aluminum and iron at meteoric velocities

DeLuca, Michael; Munsat, T.; Thomas, E.; Sternovsky, Z.

doi:10.1016/j.pss.2017.11.003

Cited by 15 publications

(25 citation statements)

References 23 publications

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“…It is separated from the high‐vacuum beamline of the dust accelerator by a two‐stage differential pumping system. The setup used for this experiment was described in detail by Thomas et al () and has been used to observe and characterize the ionization process that occurs during the ablation of particles at velocities >10 km/s (DeLuca et al, ; Thomas et al, ). For the experiments described here, aluminum particles with radii between 140 nm and 2.1 μm were shot at speeds of 1–10 km/s into air, argon, carbon dioxide, and nitrogen gases held at 0.20 Torr.…”

Section: Experimental Methodsmentioning

confidence: 99%

High‐Speed Drag Measurements of Aluminum Particles in Free Molecular Flow

DeLuca

Sternovsky

2019

JGR Space Physics

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High‐speed drag in a free molecular flow is still poorly understood despite playing an important role in a variety of physical situations, including meteor ablation in the upper atmosphere, the orbits of satellites, and the dynamics of cosmic dust grains. To measure drag at high speeds, small aluminum spheres 0.1–2.1 μm in radius were shot at 1–10 km/s into air, N2, Ar, and CO2 using an electrostatic dust accelerator. The measured drag coefficient in air is Γ = 1.29 ± 0.13, with similar values for the other gases. The measurement constrains the heating coefficient to Λ = 0.58 ± 0.37 in air assuming the gas molecules reflect diffusely from the particles' surfaces. The drag appears to be independent of the molecular structures of the four gases tested but has a slight dependence on molecular mass. The drag is also higher than frequently assumed, which has implications for the modeling of high‐speed objects in free molecular flows.

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Section: Experimental Methodsmentioning

confidence: 99%

High‐Speed Drag Measurements of Aluminum Particles in Free Molecular Flow

DeLuca

Sternovsky

2019

JGR Space Physics

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“…Slattery & Friichtenicht (1967); Friichtenicht et al (1968)) or estimated from meteor measurements. While the range in luminous efficiency estimates is very large (Subasinghe et al, 2017), recent laboratory measurements of the ionization efficiency (DeLuca et al, 2018;Thomas et al, 2016) are in comparatively better agreement with the theoretical estimates from Jones (1997). Moreover, both measurements and theory suggest a rapid drop in ionization efficiency for speeds below 20 km/s.…”

Section: Introductionmentioning

confidence: 78%

Coordinated Optical and Radar Measurements of Low Velocity Meteors

Brown,

Weryk

2020

Preprint

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To better estimate which luminous efficiency (τ) value is compatible with contemporary values of the ionization coefficient (β), we report a series of simultaneous optical and specular echo radar measurements of low speed (v < 20 km/s) meteors. We focus on the low speed population as secondary ionization is not relevant and the initial trail radii are small, minimizing model assumptions required to estimate electron line density.By using the large decrease in expected ionization coefficient at such low speeds, we attempt to better define the likely ratio of photon to electron production. This provides an estimate of the probable luminous efficiency, given that recent lab measurements of ionization efficiency agree with established theory (Jones, 1997;DeLuca et al., 2018) suggesting β is more constrained than τ.Optical measurements were performed with two pairs of autonomously operated electron-multiplied charge coupled device cameras (EMCCDs) co-located with the multi-frequency Canadian Meteor Orbit Radar (CMOR) (Brown et al., 2008). Using the timing and geometry of individual meteors measured by both the radar and multi-station EMCCD systems, the portion of the optical lightcurve corresponding to each specular radar echo is measured and the received echo power used to estimate an electron line density. A total of 1249 simultaneous EMCCD and radar meteors were

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“…The high ejection speeds, together with their low velocities Wiegert relative to Earth (4-12 km/s, peaking at 9), result in a very broad radiant extending for tens of degrees centered roughly at RA=0 • , Dec = -50 • . These meteors will be fainter than usual for their size due to the rapid drop in ionization production (Jones 1997;DeLuca et al 2018) and light production (Subasinghe & Campbell-Brown 2018) by meteors at such low speeds.…”

Section: Impact On 1 Oct 2022 Direct Arrivalmentioning

confidence: 97%

On the Delivery of DART-ejected Material from Asteroid (65803) Didymos to Earth

Wiegert

2020

Planet. Sci. J.

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The DART spacecraft is planned to impact the secondary of the binary asteroid (65803) Didymos in 2022, to assess deflection strategies for planetary defense. The impact will create a crater and release asteroidal material, some of which will escape the Didymos system. Because the closest point of approach of Didymos to Earth's orbit is only 6 million km (about 16 times the Earth-Moon distance), some ejected material will make its way sooner or later to our planet, and the observation of these particles as meteors would increase the scientific payout of the DART mission. The DART project may also represent the first human-generated meteoroids to reach Earth, and a test case for human activity on asteroids and its eventual contribution to the meteoroid environment and spacecraft impact risk. This study examines the amount and timing of the delivery of meteoroids from Didymos to near-Earth space.This study finds that very little DART-ejected material will reach our planet, and most of that only after thousands of years. But some material ejected at the highest velocities could be delivered to Earth-crossing trajectories almost immediately, though at very low fluxes. Timing and radiant directions for material reaching Earth are calculated, though the detection of substantial numbers would indicate more abundant and/or faster ejecta than is expected.The DART impact will create a new meteoroid stream, though probably not a very dense one. However, larger, more capable asteroid impactors could create meteoroid streams in which the particle flux exceeds that naturally occurring in the Solar System, with implications for spacecraft safety.

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The ionization efficiency of aluminum and iron at meteoric velocities

Cited by 15 publications

References 23 publications

High‐Speed Drag Measurements of Aluminum Particles in Free Molecular Flow

High‐Speed Drag Measurements of Aluminum Particles in Free Molecular Flow

Coordinated Optical and Radar Measurements of Low Velocity Meteors

On the Delivery of DART-ejected Material from Asteroid (65803) Didymos to Earth

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