Ionospheric disturbances associated with Tonga Mw7.9 earthquake —Results from Langmuir Probe Instrument onboard DEMETER satellite

摘要

Authors in this paper mainly employ Ne (electron density), and Te (electron temperature) data of Langmuir Probe Instrument (ISL) onboard DEMETER, to study the variations of electron density and electron temperature associated with strong earthquakes. Tonga Mw 7.9 earthquake case study shows that revisited orbits of 09768_1 and 09782_1 (before and after shock, respectively) within 4 months data before earthquake and 2 months data after earthquake changed significantly before earthquake. Te data recorded by 09768_1 and its revisited orbits before earthquake were lower about 1000K to 1500K than recorded after earthquake, whereas Ne data of the same orbits not occurred such distinctive changes. Ne data of 09782_1 and its revisited orbits experienced an increase from 20000cm-3 to 30000cm-3. To further understand the features of the pre-earthquake ionospheric anomalies, we examine the temporal and spatial evolution of electron density within the area of 2000km near epicenter from 1st March to 1st July 2006 and from 1st March to 1st July from 29st April 2005 to 2nd May 2005 respectively. Results show that about the 5 days ago before earthquake the electron density dropped to a relative lower level comparing to the normal days without earthquakes.