Characteristics of ionospheric anomalies before the earthquake in Indonesia on August 5，2018

Based on the observations of the ionosondes at the Darwin station in Australia near the epicenter （116.45°E, 8.33°S） of the earthquake in Indonesia on August 5, 2018 and at the Wuhan station in the magnetically conjugated area of the epicenter, and the observations of the GNSS receiver in the corresponding regions, this paper analyzed the characteristics and the mechanism of the ionospheric anomaly disturbance. The results show that both the critical frequency （ f_oF2） and time series of the ionospheric total electron content （TEC） were observed to be abnormal before the earthquake. Based on the lithosphere-atmosphere-ionosphere DC electric field coupling model and thermosphere-ionosphere-electrodynamics general circulation model （TIEGCM） from the National Center for Atmospheric Research （NCAR/HAO）, the electron density anomalies of the seismic area and the magnetically conjugated area before the earthquake are simulated. The simulation results show that TEC and maximum electron density N_mF2 of the seismic area and the magnetically conjugated area are significantly disturbed by the abnormal electric field before the earthquake.