Ionospheric variation in presunrise and postsunset period

• Main Authors: Ting-Kuo Jung, 鍾鼎國
• Other Authors: Jinng-Yen Liu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/u2p242

博士 === 國立中央大學 === 太空科學研究所 === 94 === Abstract Examining the parameters foF2、 h'F、 foEs and h'Es recorded by ionosonde to study the diurnal、 seasonal、latitudinal and solar activity variations in heights and plasma frequencies. The results show that foF2 yields maximum values at the two equatorial anomaly regions. The minimum values in the northern and southern anomaly regions appear in summer and winter, respectively. In general, the foF2 value is in proportion to the sunspot number. It is found that there are always exist ionospheric height lift in pre-sunrise and post sunset periods at higt attitude and h'F lifts in its attitude during pre-sunrise and post sunset periods. For the latitudinal distribution the pre-sunrise covers a greater range in southern hemisphere than in northern. Moreover, the pre-sunrise lifts in the northern and southern reach their maximum va1ues in winter and spring, respectively. The lifts of the post sunset appear mainly in stations HU、VA and TT of the southern hemisphere. The most clear signatures usually found in summer. The lift in altitude is also in proportion to the sunspot number. The foEs value in northern hemisphere is possibly greater than 5MHz. No obvious relationship can be found between foEs value and sunspot. h'Es lifts its altitude simply during morning period in winter and early spring and during both early morning and afternoon periods during late spring-fall. The lifts increase while the latitude decreases in the northern hemisphere. However, there is no latitudinal and solar activity effect found in the southern hemisphere. Finally, the lifts signatures in h'F and h'Es indicate that the E × B vertical drift and Zonal/meridional wind plays an important role.