What controls Rayleigh-Taylor instability growth rate and the formation of bubbles?
Monday, 15 December 2014
According to the Rayleigh-Taylor instability (RTI) growth rate mathematical expression, the vertical drift is supposed to be the primary component that controls the RTI growth rate. However, in the African sector that does not seem to be the case. In this paper we present independent ground- and space-based observations that consistently show weaker vertical drift (both dayside and evening sector) in the African sector compared with the American sector. On the other hand, observations from both satellite and recently deployed ground-based instruments have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities and scintillations compared to the American and Asian sectors. The question is if the drift is weaker in the African sector, what causes these strong bubbles that have been observed in the African sector almost throughout the night and during all seasons? Are there other mechanisms that initiate RTI growth other than vertical drift? Would it be the neutral winds that cause the long lasting bubbles in Africa? If it is the neutral wind, why are the winds unique in terms of orientation and magnitude in the African sector compared to other longitudinal sectors?