Using PBMOD to Model the Climatology of Equatorial Plasma Bubbles Observed by 
DMSP 
 
John Retterer (1) and L. C. Gentile (2) 
 
1. Air Force Research Laboratory Space Vehicles Directorate 
2. Boston College Institute for Scientific Research 
 
Space environmental sensors on polar-orbiting Defense Meteorological Satellite 
Program (DMSP) spacecraft occasionally encounter plasma density depletions when 
they cross the geomagnetic equator in the evening sector.  These equatorial 
plasma bubbles (EPBs) are observed at the times and locations when we expect 
equatorial spread F and radio-scintillation phenomena to occur.  The 
solar-cycle, seasonal, and longitudinal variations in the observation frequency 
of these depletions (determined over the past nineteen years) are similar to 
those of the scintillations.  To test our understanding of EPB formation, we 
simulated the observations using PBMOD, a suite of first-principle models of the 
ambient ionosphere and EPB formation, driven by climatological models for input 
parameters such as the plasma drift velocity.  PBMOD was developed for AFRL’s 
Communication/Navigation Outage Forecasting System (C/NOFS) mission.  Maps of 
the model calculations of EPB frequencies at 840 km as fun ctions of season and 
longitude exhibit features similar to the DMSP observations, including the expected 
peaks in EPB frequency near the equinoxes, an additional winter peak in the American 
sector, a summer peak in the Pacific sector, and the proper trends with solar-cycle 
phase.  Adjusting the model to reproduce the DMSP EPB occurrence frequencies in 
detail will allow us to fine-tune both the PBMOD model and the empirical driver 
models for the C/NOFS mission.