Abstract Mesoscale ionospheric irregularities are statistically investigated using an unprecedented 19‐year long‐term global GNSS (Global Navigation Satellite System) TEC (total electron content) data set. These irregularities are represented by ionospheric fluctuations within a 5 3.75 (latitude by longitude) region and a timeframe of 15 min. These fluctuations are derived from the GNSS differential TEC data and are primarily caused by medium scale traveling ionospheric disturbances (MSTIDs). This analysis focuses on Eastern American longitude sectors while comparing them to Asian and African sectors. (a) Global mesoscale irregularities at midlatitudes are characterized by the enhanced intensity during solstice seasons. In the winter hemisphere, the intensity peaks by day, and in summer, by night. The enhanced wintertime irregularity is consistent with gravity wave (GW) activities observed in the stratosphere. This study also explores the potential influence of the South American GW hotspot. (b) At equatorial latitudes, the absolute intensity exhibits semiannual variations, maximizing in equinox at Asian and African longitudes; in Eastern American sectors, highly elevated intensities persist throughout the entire September‐March period, peaking in the December solstice. The relative intensity, however, is much enhanced at night during solstices. (c) Hemispheric conjugacy of the enhanced intensity of nighttime irregularities extends from mid‐to equatorial latitudes during solstices, particularly under low solar activity. These enhanced solstitial irregularities constitute a fundamental mode of global ionospheric variability, and the increased relative intensity of equatorial irregularities may therefore reflect modulation of this underlying background state.
Zhang et al. (Sun,) studied this question.