Abstract. As a proxy of the Rayleigh-Taylor instability growth rate for equatorial plasma bubbles, we investigate the flux-tube integrated F-region Pedersen conductivity (Σ_P^F) using the electron density profiles (EDPs) provided by the Global Ultraviolet Imager (GUVI) on board the Thermosphere Ionosphere and Mesosphere Energetics and Dynamics (TIMED) satellite. The investigation is conducted using the EDPs obtained in the Atlantic sector at 19:00-22:00 LT during 4–17 August and 6-16 December 2002. The seasonal difference of the strength and location of the equatorial ionization anomalies (EIAs) induces a significant difference in the deduced Σ_P^F. Much stronger EIAs are created at higher altitudes and latitudes in December rather than in August. At 19:00–20:00 LT, the peak value of the Σ_P^F has 23 mhos at 1100 km apex height during 14–16 December and 18mhos at 600 km during 15–17 August. The Σ_P^F decreases as local time progresses. Therefore, Σ_P^F provides a preferred condition for the growth of bubbles to higher altitudes at 19:00-20:00 LT than at later hours, in December rather than in August in the Atlantic sector.