Yanli Hu

Physical mechanism of the electric field amplification in the mid-latitude ionosphere over active tectonic faults

The issue of seismo-ionospheric anomaly is noticeable increasingly. In this paper we use a model for the generation of the electric field in the ionosphere by an external current on the Earths surface to calculate the electric field in the ionosphere over the forthcoming earthquake preparation area. At the selected parameters the horizontal electric field in the ionosphere reaches ∼10mV/m, while the magnitude of the vertical electric field disturbance on the Earths surface is limited by 100V/m. Then we discuss the influence of the anomalous electric field on the ionosphere characteristics. It leads to a perturbation in the critical frequency of F2 layer (foF2). We find the result is consistent with the observations.

Gradual reduction in ionospheric F2 region before 2013 Lushan earthquake: contributed to the forthcoming earthquake or solar activity?

Ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction. However, because of the high variability of ionosphere, a real caution should be adopted before attributing the observations to seismo-ionospheric precursors (SIPs). In an investigation of contradictory results in ionospheric variation before 2013 Lushan earthquake, we examine the ionospheric variation versus solar activity. In order to assess the influence of solar activity of 27-day periodicity on ionospheric variation, a quadratic regression model is developed by using the data of F2-layer critical frequency (foF2) in April of 2008-2014. Using the model, ionospheric variation before the 2013 Lushan earthquake is analyzed. The results show that foF2 was strongly correlated with solar activity index, F10.7, and had a low correlation with the remaining by eliminating the contribution of solar radiation, which indicates that the gradual reduction in foF2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake.

Anomalous enhancement of the ionospheric TEC before Haiti earthquake on 12 January 2010

A major earthquake (M=7.3) occurred in Haiti (18.5°N, 72.5°W) at 21:53 UT on 12 January 2010. On the basis of regular GPS observations from the International GNSS service (IGS) network, Global Ionospheric Maps (GIMs) of total electron content (TEC) from 27 December 2009 to16 January 2010 were analysed. It was shown that there was a significant enhancement of TEC around the epicentre on 11 January 2010, with a maximum of ∼10TECu during 20:00–22:00UT. Taking into account of very quiet solar and geomagnetic activities during this period, we can conclude that the observed anomalous enhancement of the ionospheric TEC was likely associated with the imminent earthquake.