Photochemistry and dynamics in thermospheric intertropical arcs measured by the WIND Imaging Interferometer on board UARS: A comparison with TIE-GCM simulations
✍ Scribed by G. Thuillier; R.H. Wiens; G.G. Shepherd; R.G. Roble
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 622 KB
- Volume
- 64
- Category
- Article
- ISSN
- 1364-6826
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✦ Synopsis
The intertropical arcs are bands of enhanced nightglow O( 1 D) 630 nm emission observed at 15 • north or south of the magnetic dip equator. Ground-based measurements and measurements from early satellites established their main properties, including a seasonal e ect that locates the more prominent of the arc structures on the winter side of the geomagnetic equator. Theoretical considerations show that asymmetry of the arc system is caused by transequatorial neutral winds pushing ionization along the magnetic ÿeld lines upward and downward into the recipient hemisphere, where recombination and therefore nightglow emission is then enhanced. Seasonal variations of arc intensity and location are a direct consequence of the seasonal variation of the projection of the meridional winds along the magnetic ÿeld lines on both large and small scales.
The WIND Imaging Interferometer on UARS o ers the ÿrst opportunity to measure the wind and the nightglow enhancement simultaneously across the magnetic equator, and its measurements conÿrm these earlier understandings, in particular the longitudinal ÿne structures shown by the Orbital Geophysical Observatory 4 and 6. Furthermore, such observations are also consistent with simulation of emission rate and wind generated by the thermosphere-ionosphere electrodynamics general circulation model. This veriÿcation lends support to equatorial spread-F theories that rely upon transequatorial winds for the suppression of the Rayleigh-Taylor instability.