Ionospheric Disturbances after 2010 Merapi Eruption: The Biggest Amplitude of Disturbances by Volcano Eruption
Cahyadi Nur Nur Cahyadi, Geodesy and Surveying Laboratory, Geomatics Engineering Department Institut Teknologi Sepuluh Nopember, Surabaya-Indonesia, Indonesia
Contact First Author: Cahyadi Nur Nur Cahyadi; cahyadi@geodesy.its.ac.id
English Abstract:
Global Positioning System (GPS) satellite orbit was located on the 20,000 km above earth surface. Those satellites transmitted two kind of L band signals which were L1 (1.5 GHz) and L2 (1.2 GHz). The signals were transmitted by satellites trough ionosphere then it was received by receiver in the earth surface. Because of this transmission method, we could observe electron density in ionosphere specially F layer which was called by Total Electron Content (TEC). Variation of ionosphere was caused by seismic wave propagation from earthquake, tsunami or volcano eruption. Seismic propagation was composed from three components with different velocities, Raleigh wave (velocity about 4 km/s), Acoustic wave (1 km/s) and Gravity wave ( velocity about 0.3 km/s). This research focused on the ionospheric disturbances caused by Merapi volcano eruption which seismic wave was took into account in this variation. Ionospheric disturbances research was done in several topics using GPS-TEC,a comprehensive research about near field Coseismic Ionospheric Disturbance (CID) with Indonesian GPS array (INACORS) was done by [Cahyadi and Heki,2014].
Merapi volcano erupted on the 5 November 2010 on the 19:00 UTC, this was biggest eruption during 1872. Ionospheric disturbances was detected first time on the 18:40 UTC. They were several satellites which observed the disturbances e.g satellite number 6,3, and satellite number 21. The amplitude of the disturbances was about 1.7 TECU which was the biggest amplitude of disturbances caused by volcano eruption. Ionospheric disturbances by volcano eruption was also found in Indonesia for example 2013 Kelud volcano eruption , but the disturbances was smaller than disturbances by 2010 Merapi volcano eruption.
The directivity of the disturbances was located around south-west and north-west of the volcano which was different with CID of the 2011 Sumatra earthquake which directivity of the CID followed geomagnetic field direction. The magnitude of ionospheric disturbances by 2010 Merapi volcano was positive then became normal variation, it was like CID of earthquakes. This characteristic was very different with ionospheric disturbances by Kelud volcano, the later has positive peak variation then was followed by longer oscillation.
