Fig. 7From: Review of the generation mechanisms of post-midnight irregularities in the equatorial and low-latitude ionosphereTemporal variation of the top altitudes of the FAIs observed by the EAR during the growth phase. The left vertical axis shows the altitude of the location where the EAR radar beam is perpendicular to the magnetic field line. The right vertical axis shows the apex altitude of the geomagnetic field line connecting to the point measured with the EAR (after Dao et al. 2016)Back to article page