The Variation Characteristics of the Spread-F Occurrences at Xi'an in Northwest China

Ionospheric spread-F is a subject widely studied by scholars at home and abroad in recent decades. Its occurrence probability is affected by solar activity, geomagnetic activity, season and other factors. Due to its geographical location, Xi'an has become one of the most representative cities in Northwest China. Therefore, studying the variation characteristics of spread-F occurrence probabilities in Xi'an has important strategic significance for ionospheric research in China. This paper introduces the ionoapheric observation data of Xi”an (34.13°N, 108.83°E) in the mid-latitude of China, and studies the occurrence rate and monthly and seasonal variation characteristics of spread-F during 2011. FSF and RSF frequently occurred during summer at Xi”an. The results show that in the middle latitude, the start time of spread-F is about 21 LT and continues to 05 LT. Both the higher occurrences of FSF and RSF are mainly appeared at 22, Oland 04 local times. The probability of RSF occurring at some time in winter is higher than that in spring and autumn. Although some of the results of this paper are slightly different from the previous research results, most of the results indirectly verify the previous research results. All these results are of great significance for us to understand the variation characteristics of ionospheric irregularities in China and improve the ability of space weather prediction. However, the great difference of occurrences in Xi'an station is striking and worth further studying.