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| Obscure Properties of Ionospheric Sporadic-E over Chongqing |
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| DOI：10.7643/issn.1672-9242.2023.02.017 |
| KeyWord:ionosphere sporadic-E (Es) ionogram obscure short-wave link maximum usable frequency |
| Author | Institution |
| LI Xiao |
China Research Institute of Radiowave Propagation, Shandong Qingdao , China |
| MA Li |
China Research Institute of Radiowave Propagation, Shandong Qingdao , China |
| YUE Fu-lu |
Unit 63770, PLA, Xi'an , China |
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| Abstract: |
| The work aims to obtain the obscure properties of ionospheric sporadic-E over Chongqing, and its effects on the usable frequency of high frequency links, and provide a basis for related design and operation process of radio systems. After a statistical study on ionosonding data of Chongqing station from 2008-2018, the variabilities of the critical and obscure frequencies of sporadic-E were obtained. The obscure factor was adopted to analyze the change of sporadic-E obscure factor with local time and season. Experimental data from a short-wave radio propagation link, Xinxiang-Kunming, were used to validate the change of usable frequency of the link during strong sporadic-E. The result showed that the sporadic-E over Chongqing mainly occured in daytime of summer. The peak strength of foes appeared in the morning of June, with an average critical frequency of about 8 MHz. The obscure factor reached its peak value in July with a magnitude of about 0.8, which was more significant before sunrise. The entire obscurity could happen at any local time, but occured more often before noon. The average occurrence rate of entire obscurity is about 10%, with a peak value of 21%. When strong sporadic-E occured, the lowest usable frequency of the short-wave link that propagated into the ionospheric F region and was reflected to the ground was raised especially in the daytime. On the other hand, the maximum usable frequency refracted by Es also increased, with the maximum magnitude of about 10 MHz. It is concluded that the obscure property of sporadic-E over Chongqing changes much with local time and season, but little with solar activity. The obscure magnitude reaches its peak value in the morning in summer, but it is much weak in equinoxes. When strong sporadic-E occurs, the lowest usable frequency of short-wave links relying on the ionospheric F region is raised, which leads to a reduction of usable band. Meanwhile, the highest usable frequency of links transmitted by virtue of the sporadic-E scattering in ionosphere also increases to a certain extent. |
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