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Constraining Balmer Alpha Fine Structure Excitation Measured in Geocoronal Hydrogen Observations
- Source :
- Journal of Geophysical Research: Space Physics. 122:10-10,747
- Publication Year :
- 2017
- Publisher :
- American Geophysical Union (AGU), 2017.
-
Abstract
- 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 Hα Mapper (WHAM) 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). Index Terms: Hydrogen Geocorona, Balmer-alpha Line Profile, Fabry–Perot Interferometry
- Subjects :
- Physics
010504 meteorology & atmospheric sciences
Scattering
Airglow
Balmer series
01 natural sciences
Solar cycle
symbols.namesake
Geophysics
Space and Planetary Science
Cascade
0103 physical sciences
symbols
Atomic physics
010303 astronomy & astrophysics
Excitation
0105 earth and related environmental sciences
Line (formation)
Geocorona
Subjects
Details
- ISSN :
- 21699402 and 21699380
- Volume :
- 122
- Database :
- OpenAIRE
- Journal :
- Journal of Geophysical Research: Space Physics
- Accession number :
- edsair.doi...........b2cee972ae0e3f343b3cf0983e7e47b6