A physics‐based model for the ionization of samarium by the MOSC chemical releases in the upper atmosphere

Bernhardt, P. A.; Siefring, C. L.; Briczinski, S. J.; Viggiano, Albert A.; Caton, R. G.; Pedersen, T. R.; Holmes, J. M.; Ard, Shaun G.; Shuman, Nicholas S.; Groves, K. M.

doi:10.1002/2016rs006078

Cited by 32 publications

(46 citation statements)

References 24 publications

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“…This is further corroborated by the solar‐pumped resonance fluorescence samarium simulations by Bernhardt et al . [] and is consistent with the results from the plasma kinetic model outlined below.…”

Section: Observations and Modelingsupporting

confidence: 88%

“…This is in direct contrast to the work by Bernhardt et al . [], who postulate that the chemi‐ionization rate is substantially higher due to nonequilibrium population fractions of metastable states of Sm that have significantly higher rate coefficients than Sm in equilibrium thermal populations at thermospheric temperatures. The present spectroscopic analysis of the experimental data found that a simulated Sm plasma radiance spectrum at 2000 K produced a reasonable resemblance to the spectral observations between 400 and 600 nm.…”

Section: Discussionmentioning

confidence: 99%

“…This may indicate that the steady state excited state population distribution of solar‐pumped Sm resembles that of equilibrium atoms at 2000 K. At this temperature, the average excitation energy of Sm is only 0.15 eV, with an insignificant population (~0.01%) of the metastable states identified by Bernhardt et al . [].…”

Section: Discussionmentioning

confidence: 99%

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A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

et al. 2017

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Two rocket‐borne releases of samarium vapor in the upper atmosphere occurred in May 2013, as part of the Metal Oxide Space Clouds experiment. The releases were characterized by a combination of optical and RF diagnostic instruments located at the Roi‐Namur launch site and surrounding islands and atolls. The evolution of the optical spectrum of the solar‐illuminated cloud was recorded with a spectrograph covering a 400–800 nm spectral range. The spectra exhibit two distinct spectral regions centered at 496 and 636 nm within which the relative intensities change insignificantly. The ratio between the integrated intensities within these regions, however, changes with time, suggesting that they are associated with different species. With the help of an equilibrium plasma spectral model we attribute the region centered at 496 nm to neutral samarium atoms (Sm I radiance) and features peaking at 649 nm to a molecular species. No evidence for structure due to Sm+ (Sm II) is identified. The persistence of the Sm I radiance suggests a high dissociative recombination rate for the chemi‐ionization product, SmO+. A one‐dimensional plasma chemical kinetic model of the evolution of the density ratio NSmO/NSm(t) demonstrates that the molecular feature peaking at 649 nm can be attributed to SmO radiance. SmO+ radiance is not identified. By adjusting the Sm vapor mass of the chemical kinetic model input to match the evolution of the total electron density determined by ionosonde data, we conclude that less than 5% of the payload samarium was vaporized.

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Section: Observations and Modelingsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

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A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

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“…The robust description of the plasma density distribution provided by the present paper also serves as ground truth for comparison with first‐principles modeling efforts including a study of reactions of excited states by Bernhardt et al . [] and a chemical dynamic model by Holmes et al . [].…”

Section: Introductionsupporting

confidence: 81%

Empirical modeling of plasma clouds produced by the Metal Oxide Space Clouds experiment

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The Advanced Research Project Agency (ARPA) Long‐Range Tracking And Instrumentation Radar (ALTAIR) radar at Kwajalein Atoll was used in incoherent scatter mode to measure plasma densities within two artificial clouds created by the Air Force Research Laboratory (AFRL) Metal Oxide Space Clouds (MOSC) experiment in May 2013. Optical imager, ionosonde, and ALTAIR measurements were combined to create 3‐D empirical descriptions of the plasma clouds as a function of time, which match the radar measurements to within 15%. The plasma clouds closely track the location of the optical clouds, and the best fit plasma cloud widths are generally consistent with isotropic neutral diffusion. Cloud plasma densities decreased as a power of time, with exponents between −0.5 and −1.0, or much more slowly than the −1.5 predicted by diffusion. These exponents and estimates of total ion number from integration through the model volume are consistent with a scenario of slow ionization and a gradually increasing total number of ions with time, reaching a net ionization fraction of 20% after approximately half an hour. These robust representations of the plasma density are being used to study impacts of the artificial clouds on the dynamics of the background ionosphere and on RF propagation.

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“…10.1002/2016RS005988 the effects of neutral cloud reaction with atomic oxygen, photo-ionization by sunlight, dissociative recombination of molecular ions, diffusive expansion, and optical emissions by solar pumped excited states. The outputs from SaReC are compared to radar, ionosonde, radio beacon, and optical spectra measured during the MOSC releases by Bernhardt et al [2017]. The main conclusion of this theoretical study is that dissociative recombination of the SmO + ion with electrons is the primary process that limits the cloud lifetime.…”

Section: Radio Sciencementioning

confidence: 99%

Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

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Clouds of vaporized samarium (Sm) were released during sounding rocket flights from the Reagan Test Site, Kwajalein Atoll in May 2013 as part of the Metal Oxide Space Cloud (MOSC) experiment. A network of ground‐based sensors observed the resulting clouds from five locations in the Republic of the Marshall Islands. Of primary interest was an examination of the extent to which a tailored radio frequency (RF) propagation environment could be generated through artificial ionospheric modification. The MOSC experiment consisted of launches near dusk on two separate evenings each releasing ~6 kg of Sm vapor at altitudes near 170 km and 180 km. Localized plasma clouds were generated through a combination of photoionization and chemi‐ionization (Sm + O → SmO+ + e–) processes producing signatures visible in optical sensors, incoherent scatter radar, and in high‐frequency (HF) diagnostics. Here we present an overview of the experiment payloads, document the flight characteristics, and describe the experimental measurements conducted throughout the 2 week launch window. Multi‐instrument analysis including incoherent scatter observations, HF soundings, RF beacon measurements, and optical data provided the opportunity for a comprehensive characterization of the physical, spectral, and plasma density composition of the artificial plasma clouds as a function of space and time. A series of companion papers submitted along with this experimental overview provide more detail on the individual elements for interested readers.

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A physics‐based model for the ionization of samarium by the MOSC chemical releases in the upper atmosphere

Cited by 32 publications

References 24 publications

A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

Empirical modeling of plasma clouds produced by the Metal Oxide Space Clouds experiment

Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

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