Gravity waves and irregularities in Es observed during the solar eclipse of 22 July

The ionospheric disturbances during the total solar eclipse of 22 July 2009 were observed by two ground-based high-frequency radio systems in Wuhan, China. An ionosonde recorded the ionogram every 5 min; the Wuhan Ionospheric Oblique Backscattering Sounding System detected the echo range and Doppler variations with 1-min period. We found that the periodic fluctuation in the top penetration frequency of Es (fEs) and the irregularities in the spread Es appeared and disappeared simultaneously after the eclipse maximum. Moreover, the wavelet analysis results show that the same ~35 min period are contained in the fluctuation on the fEs curve and the variation of the irregularity Doppler velocity. Atmospheric gravity waves are considered to be generated in the ozone layer during the solar eclipse and propagate upward and passed through the Es layer. The gravity waves modulated the plasma in the Es and may produce the field-aligned irregularities we have been observed.