Is there any difference in local time variation in ionospheric F2-layer disturbances between earthquake-induced and Q-disturbance events?

• Main Authors: T. Xu, Y. L. Hu, F. F. Wang, Z. Chen, J. Wu
• Format: Article
• Language: English
• Published: Copernicus Publications 2015-06-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/33/687/2015/angeo-33-687-2015.pdf

Ionospheric anomalies before earthquakes have become the subject of one of the most intensive studies in the area of ionospheric variation. The ionosphere has a large class of disturbances under quiet geomagnetic conditions, i.e., quiet time disturbances (Q disturbances). Hence, the characteristics of seismo-ionospheric anomalies obtained by statistical analysis should be compared with those of Q-disturbance events. Using the data of <i>fo</i>F2 (F2-layer critical frequency) during the whole interval of 1978–2008 (~3 solar cycles), the local time (LT) variation in Q disturbances is investigated. The results showed that a well-pronounced nighttime peak took place for positive disturbances induced by Q-disturbance events, while positive disturbances related to earthquakes predominately occurred in the daytime, especially in the afternoon LT sector. This remarkable difference in local time variation in <i>fo</i>F2 between the earthquake-triggered and Q-disturbance events is of great significance for the identification of ionospheric precursors.