Intensive GNSS radio occultation (RO) observations by side-by-side 6 satellites of FORMOSAT-7/COSMIC-2 (F7/C2) are used to study the high temporal and fine spatial resolution of the three-dimensional structures and dynamics of the electron density in the equatorial and low-latitude ionosphere. Five events are selected to study signatures at dawn, noon, dusk, and midnight sectors using the measurements taken during a one-month period. We also construct a reference of diurnal variations of the F2-peak height (hmF2) and electron density (NmF2) with 47,642 profiles within ±7.5° magnetic latitude in June-August during 2006-2010 observed by FORMOSAT-3/COSMIC (F3/C). Good agreements between F7/C2 and F3/C show that the intensive GNSS RO observation can be used to promptly examine the sunrise effect, quasi-equilibrium distribution, pre-reversal enhancement, and midnight magnetosphere-ionosphere coupling at the dawn, noon, dusk, and midnight period, respectively.