An observing system simulation experiment for FORMOSAT-5/AIP detecting seismo-ionospheric precursors

AIP (advanced ionospheric probe) on board FORMOSAT-5 is a next version and advanced generation science payload of IPEI (ionospheric Plasma and Electrodynamics Instrument) on board ROCSAT-1 (i.e., FORMOSAT-1). We examine the ion density, ion temperature, and ion velocity probed by ROCSAT-1/IPEI, as well as the global ionospheric map (GIM) of the total electron content (TEC) derived by ground-based GPS receivers during the 31 March 2002 M6.8 Earthquake in Taiwan to determine whether FORMOSAT-5/AIP can be used to detect seismo-ionospheric precursors (SIPs). It is found that in the epicenter area, the GIM TEC significantly decreases 1 - 5 days before the earthquake, while the ROCSAT-1/IPEI ion density significantly decreases and ion velocity in the downward direction anomalously increases. The anomalous decreases in the ROCSAT/IEPI ion density and the GIM TEC concurrently appear around the epicenter area 1 - 5 days before the earthquake, which suggests that FORMOSAT-5/AIP can be employed to detect SIPs. Moreover, the increase in the downward velocity implies that a westward electric field generated during the preparation earthquake period is essential.