Study On Ionospheric E-Region Field-Aligned Irregularities In Kunming

The ionospheric E-region field-aligned irregularities(FAI)is an important irregularities,and the deep knowledge of the E-region FAI is an important direction in the mid-low latitude ionosphere research.Kunming is an interesting area in mid-low latitude ionosphere study,because it is active region for the ionospheric Es event and the E-region FAI phenomenon.Based on the data obtained from the VHF coherent radar and ionosonde in Kunming,these features of E-region FAI are investigated including the morphological performances and the excitation mechanism.The main achievements are presented as follows:1.Using the data of the VHF coherent scatter radar in Kunming,the morphological characteristics of the ionospheric E-region Field-Aligned Irregularities echo are statistically analyzed.The characteristics distribution of irregularities occurrence rate,Doppler velocity and width are obtained.Meanwhile,we also analyzed the FAI echo characteristics of the diurnal variation,seasonal variation and the corresponding height variation.In addition,we also discussed the differences between Kunming and the other regions in the middle and low latitudes,and systematically explained the morphological characteristics of the FAI echo in the equatorial anomaly in East Asia.2.The close relationship is discovered between the excitation of E-region FAI and the Sporadic E.The appearance of the E-region FAI always accompany with the Sporadic E(Es)event,and a good consistency is found between the field-aligned FAI and the Es events when the difference is more than 3MHz between foEs and fbEs in post-noon,which revealed that Es is an important excitation source for the E-region FAI in Kunming.Moreover,these phenomena are sought out by the typical cases,which the virtual height of Es is approximate with the bottom of the continuous echoes,while is fluctuant accompanying the quasi-periodic echoes.