[P-EM12] Study of coupling processes in solar-terrestrial system

[PEM12-06] Ionospheric total electron content (TEC) gradient characterization in Indonesia

*MAHO NAKAMURA¹, Susumu Saito¹, Takayuki Yoshihara¹, Slamet Supriadi², Prayitno Abadi², Dwiko Unngul² (1.Electronic Navigation Research Institute, 2.National Institute of Aeronautics and Space (LAPAN), National Research and Innovation Agency of Indonesia (BRIN))

Keywords:Ionosphere, plasma bubble, ionospheric gradient, ionospheric threat model, GBAS, GNSS

In the magnetic low latitude ionosphere, there is a region with high electron density in the ionosphere called the equatorial anomaly, and a structure called plasma bubble in which the electron density depletion locally develops, causing large temporal and spatial variations in the ionospheric total electron contents (TEC). The ionosphere cause propagation delay of radio signals proportional to the TEC. It is known that the TEC variations make the differential GNSS systems difficult to work properly, because they assume similar error conditions between the user and reference stations. For example, the GNSS ground-based augmentation system (GBAS) that provide approach guidance for aircraft based on correction information created by a ground station at airport. It is important to characterize the ionospheric TEC variations to ensure the safety of aircraft. The range of parameters to characterize the ionospheric TEC variation is called an ionospheric threat model. Since GBAS is supposed to provide service around the airport, spatial variations of TEC with scale sizes of 10 km or so is important. However, it has not been well studied, especially for plasma bubbles.

To study the TEC variation of scale sizes of 10 km or so associated with plasma bubbles, closely distributed GNSS receivers are necessary. Electronic Navigation Research Institute (ENRI) in collaboration with National Institute of Aeronautics and Space (LAPAN), National Research and Innovation Agency of Indonesia (BRIN) is setting up such a network consisting of four GNSS receivers around Bandung, Indonesia. This observation will provide not only the information to characterize ionospheric TEC variation but also to study the fine structures of plasma bubbles and help understanding the mechanisms of plasma bubble generation. This is a good example of space weather projects which have both scientific and engineering/application aspects.