Determination of E region effective recombination coefficient using impulsive precipitation events

A set of sudden increases followed by slow decay has been observed in E region electron density on December 17, 1990 using the EISCAT UHF‐radar. Simultaneous photometer observations indicate that the density enhancements are caused by impulsive particle precipitation with short duration (4 ± 1 s). Effective recombination coefficient profiles in the E region are calculated from decaying electron densities using the continuity equation, and the results are compared with previous observations. It is pointed out that short‐lived particle precipitation affects the ion composition in the E region and therefore the effective recombination coefficient in this situation is different from the steady‐state value.