Satellite and Ground Based Measured Ionospheric Variations Over Seismic Active Areas
Résumé
In this study we investigate ionospheric disturbances over earthquake prone areas with two methods.The satellite based approach - in our case magnetic field measurements from CSES-01 and Swarm mission - shed light on ionospheric F-region plasma variations at low-earth orbit (LEO) altitudes around 500 km. The complemen-tary second technique is based on variations of the so-called Earth-ionosphere waveguide, the cavity between Earth’s surface and the lower ionospheric D/E (day/night) upper boundary at approx. 70-90 km altitude. Electric field ampli-tude and phase perturbations of paths between several narrowband VLF/LF transmitter and a receiver network are continuously recorded.In both cases the lithosphere-atmosphere-ionosphere coupling (LAIC) is a key area and of vital importance in order to establish the propagation char-acteristics from the seismic zone up to high altitudes. Possible mechanisms are discussed in the literature, e.g. [1], [2]. In this presentation we focus on acous-tic waves and atmospheric gravity waves (AGW) as energy-momentum trans-port channel (and filter) to connect the different regions from bottom to top.We examine events form the United States Geological Survey (USGS) earthquake catalog, assign a spatial box of a few degrees in latitude and lon-gitude around the epicenter, investigate measurements from satellite- and/or VLF/LF paths which crosses the box, and report on differences in variations prior and after the events.These findings could point to regular automated procedures in order to disentangle seismic from nonseismic ionospheric pattern and are equally important for upcoming satellite missions and extended ground based networks.