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Constraining Balmer Alpha Fine Structure Excitation Measured in Geocoronal Hydrogen Observations
Journal of Geophysical Research: Space Physics
  • D. D. Gardner, University of Wisconsin-Madison
  • E. J. Mierkiewicz, Embry-Riddle Aeronautical University
  • F. L. Roesler, University of Wisconsin-Madison
  • S. M. Nossal, University of Wisconsin-Madison
  • L. M. Haffner, University of Wisconsin-Madison
Submitting Campus
Daytona Beach
Physical Sciences
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Publication/Presentation Date

Cascade contributions to geocoronal Balmer α airglow line profiles are directly proportional to the Balmer β ∕α line ratio and can therefore be determined with near simultaneous Balmer β observations. Due to scattering differences for solar Lyman β and Lyman γ (responsible for the terrestrial Balmer α and Balmer β fluorescence, respectively), there is an expected trend for the cascade emission to become a smaller fraction of the Balmer α intensity at larger shadow altitudes. Near-coincident Balmer α and Balmer β data sets, obtained from the Wisconsin H alpha Mapper Fabry-Perot, are used to determine the cascade contribution to the Balmer α line profile and to show, for the first time, the Balmer β∕α line ratio, as a function of shadow altitude. We show that this result is in agreement with direct cascade determinations from Balmer α line profile fits obtained independently by high-resolution Fabry-Perot at Pine Bluff, WI. We also demonstrate with radiative transport forward modeling that a solar cycle influence on cascade is expected, and that the Balmer β ∕α line ratio poses a tight constraint on retrieved aeronomical parameters (such as hydrogen’s evaporative escape rate and exobase density).

American Geophysical Union
Additional Information

Dr. Haffner was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published.

Citation Information
D. D. Gardner, E. J. Mierkiewicz, F. L. Roesler, S. M. Nossal, et al.. "Constraining Balmer Alpha Fine Structure Excitation Measured in Geocoronal Hydrogen Observations" Journal of Geophysical Research: Space Physics Vol. 122 Iss. 10 (2017) p. 727 - 747
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