The relationship between the post-sunset equatorial Plasma Bubbles (EPBs) and the Rayleigh-Taylor instability growth rates gamma RT $\left({\gamma }_{RT}\right)$ was studied by means of the occurrence probabilities. EPB observations were obtained through the Rate of Total Electron Content Index (ROTI) measured by ground-based Global Navigation Satellite System (GNSS) receivers in the South American equatorial region. Data from the period 2013 to 2022 were utilized. The gamma RT ${\gamma }_{RT}$ calculations were based on F-layer vertical drift Vp $\left({V}_{p}\right)$ measurements obtained from the S & atilde;o Lu & iacute;s ionosonde (2.33 degrees S, 44.2 degrees W, dip angle: -0.5 degrees), the International Reference Ionosphere model (IRI-2016), Horizontal Wind Model (HWM-14), and Spectrometer Incoherent Scatter Model-2,000 (NRLMSISE-00). The EPB occurrence probability increased from 0% to 100% as gamma RT ${\gamma }_{RT}$ increased from 0 to 2.2x10-3s-1 $2.2\times 1{0}<^>{-3}\hspace*{.5em}{\mathrm{s}}<^>{-1}$. Additionally, the occurrence probability exhibited seasonal variations, with a gradual increase during the equinox months, minimal occurrence during the June solstice, and a sudden increase during the December solstice. We found that the occurrence probability varied with day-to-day, season and solar activity for the same gamma RT ${\gamma }_{RT}$. Equatorial plasma bubble (EPB) in the earth's equatorial and low latitude ionosphere is a large-scale plasma depletion producing a large-scale irregularity, which causes problems in the space based telecommunications and Global Navigation Satellite System (GNSS) positioning systems. Prediction and forecasting of such ionospheric irregularities are an important issue in the space technology applications. Present work tries to visualize probability of EPB occurrence at a certain location and time of the year. For this purpose, we calculated the occurrence probability using past observed data (temporal variabilities of Total Electron content (TEC) and ionospheric layer height) and ionospheric models. Our results show that the occurrence probability increases gradually when the irregularity index of the ionosphere increases. We also found that the gradual increase has a seasonal dependency, very low probability during June-July, and high probability during December-January. The relationship between the Equatorial Plasma Bubbles and the R-T instability growth rate was studied by probability of occurrence Probability gradually rises with growth rate during equinox seasons, but experiences a sudden surge during the December solstice For the same growth rate, the probability varies with the seasons and solar cycle
