Compression and rarefaction of F-region plasma caused by an atmospheric gravity wave

The Advanced Ionospheric Sounder at Halley (75° 31′S, 26° 59′W) in Antarctica has been used to observe the F-region disturbance caused by an atmospheric gravity wave. Observations at 4.5 MHz were used to examine the variations of group range, obtained from time-of-flight measurements, and of Doppler shift, derived from Fourier analysis of the quadrature components of the signal. A comparison of simultaneous values of group-range and phase-path velocities shows clear evidence of compression and rarefaction of ionization and more complicated changes in the height distribution of ionization in the oscillatory changes associated with the wave