Possible Drivers of Large Scale Traveling Ionospheric Disturbances by Analysis of Aggregated Ham Radio Contacts

Large Scale Traveling Ionospheric Disturbances (LSTIDs) are quasiperiodic electron density perturbations of the F region ionosphere that have periods of 30 min to over 180 min, wavelengths of over 1000 km, and velocities of 150 to 1000 m/s. These are seen as long slow oscillations in the bottom side of the ionosphere in data from ham radio contacts at 20 meters wavelength on roughly a third of the days in a year. They might be triggered by electromagnetic forces from above, and/or by mechanical pressures from below. The explosion of the Tonga volcano on January 15, 2022 revealed that such a LSTID could be triggered by a violent updraft from the Earth’s surface into the stratosphere and then detected in the ionosphere over the United States nine hours later. We consider other possible drivers such as the auroral electrojet, geomagnetic activity, the polar vortex, thunderstorms, zonal wind speeds, gravity wave variances, and their time derivatives in 2017.