HR: 1400h
AN: G43B-10    [Abstracts]
TI: GPS Detection and Modeling of Ionospheric Waves following the 2003 Explosion of the Soufriere Hills Volcano, Montserrat
AU: * Dautermann, T
EM: Dautermann@purdue.edu
AF: Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47906, United States
AU: Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47906, United States
AU: Mattioli, G S
EM: mattioli@uark.edu
AF: University of Arkansas, 113 Ozark Hall, Fayetteville, AR 72701, United States
AU: Lognonné, P
EM: lognonne@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris (IPGP), 4 Av. de Neptune, Saint Maur, 94107, France, Metropolitan
AB: Volcanic explosions and shallow earthquakes are known to trigger atmospheric waves that propagate at infrasonic speeds in the atmosphere. Because of the exponential decrease of atmospheric density with altitude, the wave's amplitude increases significantly as it propagates upward. Upon reaching ionospheric altitudes, coupling between neutral particles and electrons induces variations of the ionospheric electron density that are detectable by GPS measurements. We used near- and far-field GPS data from Montserrat and the other nearby islands in the Lesser Antilles to examine ionospheric perturbations following the massive dome collapse and explosion of the Soufriere Hills Volcano on July 13th 2003. The ionospheric wave was detected in the GPS- derived integrated electron content (IEC) north of the island, in an area of maximum alignment between theoretical neutral particle motion (from ray tracing) and the Earth's magnetic field, and travels at an apparent velocity consistent with sound speed. Frequency content of the IEC showed peaks at 1 mHz and 4 mHz indicating both a gravity and an acoustic component. The data are consistent with previous observations of atmospheric perturbations after volcanic explosions. To model the acoustic part of the perturbation, we utilized the raytracing equations to follow the path of the wave through the atmosphere. We then coupled the neutral disturbance to the ionosphere by integrating the continuity equation for the charge density with a Chapman electron density distribution. Summation over all ray paths yields a synthetic IEC comparable to the GPS-derived observations.
DE: 2435 Ionospheric disturbances
DE: 2439 Ionospheric irregularities
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 3367 Theoretical modeling
DE: 8409 Atmospheric effects (0370)
SC: Geodesy [G]
MN: 2007 Joint Assembly