Abstract. It is generally considered that the perturbation electric field generated by the charge accumulation caused by the current divergence is the driving force for Rayleigh–Taylor instability (RTI) in plasma. However, in previous calculation of the linear growth rate of RTI the current continuity equation was applied, which means the contribution of charge accumulation to the growth of RTI was ignored. Applying the perturbation electric field and the current continuity equation simultaneously in calculating the linear growth rate of RTI of the ionospheric F layer will give erroneous results. In this paper, we calculated the linear growth rate of RTI with the standard instability analysis method. The charge conservation equation was used in the calculation instead of the current continuity to study the contribution of charge accumulation to the growth of RTI. The results show that the contribution of charge accumulation to the linear growth rate of RTI is proportional to the ratio of Alfvén speed to the light speed. In ionospheric F layer the ratio is small, the contribution of charge accumulation to the growth of RTI is negligible. This indicates that the previous physical description of the RTI in the ionospheric F layer is wrong and a new physical description of RTI is needed. In the new physical description perturbation electric field and charge accumulation is not the cause, but the result of RTI. In ionospheric layer, background electric field and neutral wind velocity have no effect on the linear growth rate of RTI.