Ionospheric response to the ultrafast Kelvin wave in the MLT region

The modulation of the ultrafast Kelvin wave (UFKW) on the equatorial ionosphere is investigated, using satellite neutral wind and temperature observations in the mesosphere/lower thermosphere (MLT) and ground-based global maps of total electron content (TEC) observations. The UFKW signatures are identified in the least squares fitting spectra for MLT zonal wind, temperature, TEC, and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) electron density profiles, providing strong evidence for the neutral-ion coupling through the UFKW. The periods of the UFKW are mostly confined within 2-5.5days. The UFKW in zonal wind and temperature maximize in the equatorial regions, whereas the UFKW band-pass perturbations in electron density peak at the equatorial ionization anomaly (EIA) crests with minima at the equator. The UFKW band-pass perturbations in TEC show consistent seasonal variability with the UFKW in the MLT region, including the intraseasonal oscillations with periods of 20-70days. The long-term variability of the absolute UFKW band-pass amplitudes in TEC is in-phase with solar cycle with maximum amplitude of similar to 7-8 (similar to 1-2) total electron content unit (TECU; 1 TECU = 10(16) el m(-2)) during solar maximum (minimum) years, while the relative amplitudes show little solar activity dependence. The COSMIC electron density profiles show that the UFKW band-pass perturbations maximize at similar to 300-400km with fountain-like spatial distributions, indicating the modulation of the UFKW on the EIA through electrodynamics.