Rayleigh-Taylor Instability growth rates calculated using the global assimilative ionospheric model (GAIM)

The Ionosphere-Thermosphere (IT) is a driven system largely determined by its primary forcing mechanisms, i.e., magnetosphere-ionosphere-thermosphere (M-I-T) coupling. The growth/suppression of equatorial irregularities is controlled by the Rayleigh-Taylor Instability (RTI) process, which is mostly determined by the IT dynamics and ambient ionospheric state. Data assimilation (DA) allows for the combination of observational data and physics-based models for promising applications in modeling day-to-day variability, near real time forecasting, and specific data event studies [1][2][3]. The IT is different from the classical meteorological DA system in that the forcing terms in the IT system play a more important role to the evolution than the initial condition as in the meteorological system. The focus of this study is to estimate the fluxtube integrated RTI growth rate (RTI-GR) using the global assimilative ionospheric model (GAIM). We compare the estimated RTI-GR between several models. Comparisons are conducted to understand the effects of different empirical model (EM) drivers and DA techniques. We compare EMs, such as those that represent the horizontal wind, and DA approaches. The applicability of GAIM-KF vs. GIAM-4DVAR DA to predict ionospheric irregularities is discussed.