A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases. Issue 5 (3rd May 2017)

• Record Type: Journal Article
• Authors: Holmes, Jeffrey M.; Dressler, Rainer A.; Pedersen, Todd R.; Caton, Ronald G.; Miller, Daniel
• Is Part Of: Radio science. Volume 52:Issue 5(2017:May)
• Page Start: 521
• Page End: 538
• Publication Date: 2017-05-03
• Subjects: ionosphere -- active experiments -- sounding rockets -- chemical release -- ionospheric modification; Radio meteorology -- Periodicals; Radio wave propagation -- Periodicals; 621.38405
• DOI: 10.1002/2016RS006084
• Languages: English
• ISSNs: 0048-6604

Abstract

Abstract: 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 N SmO / N Sm ( 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. Key Points: Spectral observations from 400 to 800 nm of ionospheric Sm vapor releases Temporal evolution of broad molecular feature suggests SmO origin, not SmO + Sm I emissions persist, indicating efficient dissociative recombination of SmO +