Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8140517 | Journal of Atmospheric and Solar-Terrestrial Physics | 2013 | 7 Pages |
Abstract
We report on the first observation of a descending layer of atomic potassium (K) in the thermosphere. This observation was made with the K Doppler lidar at the Arecibo Observatory in Puerto Rico (18.35°N; 66.75°W) on 12 March 2005. The layer was first observed before 08:00 UT (04:00 AST) centered near 145 km with the vertical extent up to â¼155 km, and then it descended to near 126 km just over 2 h later at dawn. The descent rate of 2.56±0.38 m/s matches the vertical phase speed of the GSWM09-computed semidiurnal tide between 120 and 150 km. This also matches the descent rates of the thermospheric semidiurnal tides measured at Arecibo. Although the K density above 120 km remains less than 1 cmâ3, its presence is unequivocal and has strong similarities to the neutral iron (Fe) layers in the thermosphere over 155 km recently discovered by lidar observations at McMurdo, Antarctica. The thermospheric K layer is plausibly explained by radiative electron recombination with K+ within a tidal ion layer, which descends with the downward phase progression of the semidiurnal tide. Based on the production rate of K atoms and using current knowledge of tidal ion layer composition, we calculate an electron density of near 5Ã104 cmâ3 and K+ concentration of 650 cmâ3 at 135 km immediately prior to the layer formation. This discovery of a thermospheric K layer, coupled with the McMurdo discovery of similar Fe layers, may lead to a new approach to studying the thermosphere in the altitude range of â¼100-150 km with resonance fluorescence lidars.
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Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Jonathan S. Friedman, Xinzhao Chu, Christiano Garnett Marques Brum, Xian Lu,