By using ionosonde data recorded at Chiang Mai (18.8° N, 98.9° E, magnetic latitude is 9.1° N), Puer (22.7° N, 101.1° E, magnetic latitude is 12.9° N), and Leshan (29.6° N, 103.7° E, magnetic latitude is 19.8° N), the statistical features of different types of spread F (SF) occurrence at low and middle latitudes were analyzed in this study. The results showed that the SF occurrence had obvious local time, latitude, and SF-type variations. The range spread F (RSF) occurrence in equinox months decreased with the increase in latitude, while the frequency spread F’s (FSF) occurrence rate in the summer months increased and the onset time of FSF became earlier when the latitude increased. The generation of SF depends on the SF type. A plasma bubble excited by the generalized Rayleigh–Taylor instability (GRT) at the equator is more likely to produce RSF, while nighttime medium-scale traveling ionospheric disturbances (MSTIDs) induced by Perkins instability at middle latitudes is the main reason for the generation of FSF.

中文翻译：

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第24个太阳周期下降阶段亚洲经度F分布特征的纬度差异

通过使用在清迈（18.8° N，98.9° E，磁纬 9.1° N）、普洱（22.7° N，101.1° E，磁纬 12.9° N）和乐山（29.6° N， 103.7°E，磁纬19.8°N），本研究分析了中低纬度不同类型展布F（SF）发生的统计特征。结果表明，SF发生具有明显的当地时间、纬度和SF类型变化。随着纬度的增加，春分月的范围展F（RSF）发生率降低，而夏季月份的频展F（FSF）发生率增加，随着纬度的增加FSF的发生时间提前。SF 的产生取决于 SF 类型。在赤道由广义瑞利-泰勒不稳定性 (GRT) 激发的等离子体气泡更有可能产生 RSF，