Climatology of ionospheric Sporadic E Layer : Examination of Wind Shear Theory

• Main Authors: Kuan-Ting Chen, 陳冠廷
• Other Authors: Yen-Hsyang Chu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/10140004731560594998

碩士 === 國立中央大學 === 太空科學研究所 === 101 === On the basis of GPS radio occultation (RO) technique, we develop a method to extract ionospheric sporadic E (Es) layer from COSMIC-measured ionospheric data (e.g., GPS signal signal-to-noise ratio, L1 and L2 excess phases and RO-retrieved electron density) to investigate the climatology of the Sporadic E layer. The results show that there is salient summer-winter asymmetry in the occurrence rate of the Es layer, namely, higher in summer hemisphere and lower in winter hemisphere. In addition, there is a strong tendency for the Es layer to descend with local time that is in harmony with the diurnal or semi-diurnal tidal motion, depending on season and latitude region. In order to realize the physical process responsible for the climatology of the COSMIC-measured Es layer, we simulate the temporal and global distribution of the occurrence of the Es layer in accordance with wind shear Theory. We calculate vertical ion drift velocity based on empirical models of the ionosphere, including HWM07, MSIS00, IGRF. The ferric ion (Fe+) density calculated from Whole Atmosphere Community Climate Model(WACCM) is used to obtain ferric ion vertical flux. The simulation results show that the seasonal asymmetry of the Sporadic E layer occurrence rate between the summer and winter hemispheres is very likely caused by the neutral wind shear in the Es region.