Ionospheric Disturbance in Indonesia during Solar Flare using GPS Observations

Electromagnetic waves transmitted by Global Navigation Satellite System (GNSS) are delayed when they travel through ionosphere layer due to free electrons in that layer. This delay could be used to deduce the variation in ionosphere, through the quantity known as Total Electron Content (TEC). The variability of the TEC in the ionosphere is affected by solar activity, such as solar flares. When a solar flare occurs, which is characterized by a strong and sudden increase in X-ray intensity, it will result in an increase in the electron density in the ionosphere, which is known as ionospheric disturbances. The increase of electron in the ionosphere increases the absorption of HF radio wave energy which can also turn off HF radio communications and cause significant errors in GNSS measurements. This study observed the SID above Indonesia which was disrupted by a solar flare that occurred on November 8, 2013, with class X1.1 angstroms. We use the Sumatran GPS Array (SuGAR) station with observation epochs every 30 seconds to estimate the TEC. The results showed that there was a sudden and simultaneous increase of all observed satellites namely GPS PRN 2, 4, 5, 9, 10, 17, 24, 26 and 28. SID occurred at 11:25:30 LT with a TEC amplitude of 1.05 - 3.94 TEC Unit. The detection time of the SID corresponds to the solar flare's time observed from the GOES satellite with a delay of ∼5 minutes.