Browsing by Subject "01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous"

There are many reports on the occurrence of anomalous changes in the ionosphere prior to large earthquakes. However, whether or not these changes are reliable precursors that could be useful for earthquake prediction is controversial within the scientific community. To test a possible statistical relationship between ionospheric disturbances and earthquakes, we compare changes in the total electron content (TEC) of the ionosphere with occurrences of 1279 M≥ 6.0 earthquakes globally for 2000–2014. We use TEC data from the global ionosphere map (GIM) and an earthquake list declustered for aftershocks. For each earthquake, we look for anomalous changes in GIM-TEC within 2.5° latitude and 5.0° longitude of the earthquake location (the spatial resolution of GIM-TEC). Although case studies of individual earthquakes that used short periods of data sometimes yield GIM-TEC changes that were considered possible earthquakerelated phenomena, our analysis has not found any statistically significant changes prior to earthquakes when considering all 1279 earthquakes together. Thus, we have found no evidence that would suggest that monitoring changes in GIM-TEC might be useful for predicting earthquakes.

For the phase refraction index of high frequency (HF) waves in the ionospheric medium exists a well-established theory. However, under the Quasi-Longitudinal (QL) conditions, scientific literature presents various formulas that are not equivalent and that, in some cases, give rise to wrong results. In the present study, further consequences of Booker's rule are discussed, illustrating the validity ranges of the above-mentioned approximate formulas; and the different regimes for applying such QL formulas are described, along with the consequences in simulating the ionospheric HF ray-tracing, oblique and vertical sounding, and absorption.