A climatology of equatorial plasma bubbles from DMSP 1989–2004

After examining evening sector plasma density measurements from polar‐orbiting Defense Meteorological Satellite Program (DMSP) spacecraft for 1989–2004, we have established a statistical database of more than 14,400 equatorial plasma bubble (EPB) observations. EPBs are irregular plasma density depletions in the postsunset ionosphere that degrade communication and navigation signals. In general, the DMSP observations support Tsunoda's (1985) hypothesis that EPB rates peak when the terminator is aligned with the Earth's magnetic field, but unpredicted offsets are also evident in many longitude sectors. Plots of EPB rates for solar cycle phases: maximum 1989–1992 and 1999–2002, minimum 1994–1997, and transition years 1993, 1998, and 2003 reveal significant differences in the climatologies for solar maximum and minimum, between the two solar maxima, and in the transition years. To assess local time effects on EPB rates, we also compare observations from F12, F14, F15, and F16 at slightly different postsunset local times for 2000–2004. This study was undertaken to facilitate improvements in ionospheric models in preparation for the Communication/Navigation Outage Forecasting System (C/NOFS) mission.