Analysis of Tsunami Traveling Ionospheric Disturbances Due to Tsunami Using The GNSS-TEC Method

The Global Navigation Satellite System (GNSS) is a navigation satellite system that provides information on the position and speed of 3D objects on the earth's surface. GNSS is increasingly being used in the field of survey and mapping work because of its high measurement accuracy, and its use can be done anywhere and anytime. The working principle of GNSS is to transmit digital data from satellites to receivers on the earth's surface. The digital data is carried by a carrier microwave called the L-band. In the propagation path, the carrier microwave will pass through the ionosphere and troposphere. The collection of electrons contained in the ionosphere layer and the wet & dry components in the troposphere can disrupt the wave propagation path to be slower. This slow propagation will cause the accuracy of the results obtained during the measurement to be more inaccurate. The delayed wave data can obtain the Total Electron Content (TEC) value in the ionosphere layer. TEC is a value that represents the electron density in 1m² in the ionosphere. The vertical movement of the land surface and seawater can suddenly cause acoustic waves that propagate towards the ionosphere layer, which causes the electron density to decompose. These disorders are known as Traveling Ionospheric Disturbances (TID). In this study, we studied the characteristics of the change in electron density in the ionosphere caused by the tsunami. The tsunami observed was a tsunami in the territory of Indonesia due to the eruption of Mount Tonga on January 15, 2022. The change in electron density was calculated from the significant difference in the TEC value during the tsunami propagation time. The calculation of the change in the TEC value is called the TEC reduction. TEC reduction is obtained by calculating the TEC value, calculated with the reference value of the polynomial curve. The result of the TEC reduction, which has a change in value at the same time as the tsunami is coming, is most likely the TID of the tsunami.