HR: 15:25h
AN: V23E-08    [Abstracts]
TI: GPS Detection, Modeling and Energy Estimation of the Ionospheric Wave following the 2003 Explosion of the Soufriere Hills Volcano, Montserrat
AU: * Dautermann, T
EM: Dautermann@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr, West Lafayette, IN 47907, United States
AU: Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr, West Lafayette, IN 47907, United States
AU: Mattioli, G S
EM: mattioli@uark.edu
AF: University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701, United States
AB: Volcanic explosions or shallow earthquakes are known to trigger acoustic and gravity waves that propagate at infrasonic speeds in the atmosphere. At ionospheric heights, coupling between neutral particles and free electrons induces variations of the electron density that are detectable using dual-frequency GPS measurements. In this study, we use GPS data collected at continuous stations in the Caribbean to detect and quantify the ionospheric perturbation triggered by the explosion of the Soufriére Hills Volcano on July 13th, 2003 (Montserrat island, Lesser Antilles). We find the disturbance in an area of maximum alignment between the direction of theoretical neutral particle motion (from ray tracing) and the Earth's magnetic field, located northwest of the island, as predicted theoretically. Its frequency content shows peaks at 1 mHz and 4 mHz indicating both a gravity wave and an acoustic component, consistent with previous observations and theoretical considerations. We retrieve a horizontal velocity component of 338 m/s for the acoustic component which, given the sound speed at the maximum electron density height, implies upward propagation at an elevation angle of 63°. We model the acoustic component of the perturbation as resulting from an explosive source at ground level (N-wave pulse). We use a ray tracing technique to propagate the neutral pressure wave in the atmosphere, accounting for the dispersive characteristics of the atmosphere while conserving total acoustic energy. We couple the neutral disturbance to electron flow by integrating the continuity equation for the charge density. We then derive synthetic integrated electron content values comparable to the GPS measurements by integrating over all rays crossing satellite-to-receiver line-of-sights, accounting for the satellite displacements. Synthetic ionospheric waveforms match the observed ones well. We minimize the misfit between observed and model waveforms to estimate the total acoustic energy of the Soufriére Hills explosion.
DE: 2435 Ionospheric disturbances
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 3367 Theoretical modeling
DE: 8409 Atmospheric effects (0370)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting