Ionospheric Storm Caused in 2015 by Intense Geomagnetic Storms over Metro Manila, Philippines

The 2015 intense geomagnetic storms were significant event in relatively weaker solar cycle 24. In this paper, we explored the impacts of the 2015 intense geomagnetic storms and the response of the ionosphere over Metro Manila, Philippines. We obtained the data from the World Data System for Geomagnetism, Kyoto for the Kp and Dst indices; Space Radiation Lab at California Institute of Technology (SRL-CalTech) for the solar wind speed (v
sw
) collected by the Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM) and the Advanced Composition Explorer (ACE) magnetometer for the Bz (nT) values. The total electron content was obtained from a GNSS station (PIMO) in Quezon City, Philippines, through the International Centre for Theoretical Physics (ICTP) web service. The quiet days were also acquired from the same site. Our investigation have shown that the ionosphere over the PIMO station depletes its electron density (negative storm) after reaching the minimum (during the recovery phase) and will remain for at least ~20 hours. Contrary to the CME-driven storm, the CIR-induced event in October 2015 produced negative storm (with very few and weak positive). Our results were mostly consistent with the time delay on the occurrence of a negative storm. In addition, a greater Dst minimum does not guarantee the type of storm and further analysis is required.