One important characteristic of longitudinal variability of the ionosphere is the global wavenumber-4 signature. Recent investigations have focused mainly on the climatological pattern during daytime and evening sectors. We investigate the day-to-day variability of the wavenumber-4 structure of the longitudinal ionospheric density distribution using the global total electron content (TEC) measurements from Global Positioning Systems receivers on the ground. The quiet time (Kp ≤ 3) day-to-day occurrence of the wavenumber-4 is obtained during periods of low solar flux conditions for the years 2008 and 2009. We find that the wavenumber-4 structure occurs at all local time sectors; however, the daytime TEC wavenumber-4 structures are clearer and can persist until the midnight hours. The most significant occurrence is observed during the 1000-2400 LT sector while the minimum number of wavenumber-4 structure is observed between the 0400 and 0600 LT sector. Around the nighttime sector, more wavenumber-4 occurrence is observed during the premidnight sector than the postmidnight hours. The seasonal occurrence probability of the wavenumber-4 pattern is at a maximum during the March-April equinox and June-July solstice. December-January is the period when the wavenumber-4 occurrence is less dominant than the rest of the year. Key Points We investigate the day-to-day variability and occurrence of the wavenumber-4The occurrence of the wavenumber-4 pattern is seasonal and local time dependent ©2013. American Geophysical Union. All Rights Reserved.