Observations of traveling ionospheric disturbances driven by gravity waves from sources in the upper and lower atmosphere

Abstract

The observed traveling ionospheric disturbances (TIDs) are attributed to atmospheric gravity waves generated by auroral sources in the lower thermosphere or gravity waves generated in the troposphere by midlatitude weather systems. TIDs are observed by the Poker Flat Incoherent Scatter Radar (PFISR), the Super Dual Auroral Radar Network (SuperDARN), multipoint and multifrequency continuous Doppler sounders, and Global Navigation Satellite System (GNSS) receivers using the total electron content (TEC) mapping technique. At high latitudes, the solar wind-magnetosphere-ionosphere-thermosphere coupling modulates the dayside ionospheric convection and currents, the source of the equatorward-propagating TIDs. The horizontal equivalent ionospheric currents are estimated from the ground-based magnetometer data using an inversion technique. At midlatitudes, the eastward- to southeastward-propagating medium-scale TIDs that were observed by the high-frequency (HF) Doppler sounding system, as well as in the detrended TEC, are attributed to gravity waves that are generated by geostrophic adjustment processes and shear instability in the intensifying low-pressure systems and are identified in the stratosphere using the ERA5 meteorological reanalysis.