Abstract Equatorial plasma bubbles are ionospheric structures characterized by plasma densities below the background level and are influenced by season, local time, longitude, solar and geomagnetic activity, and the offset between geographic and magnetic poles. Using density measurements from the Ionospheric Connection Explorer (ICON) satellite between 2020 and 2022, together with a rolling‐ball algorithm and irregularity index criteria, we examine the climatology and evolution of bubbles, along with the corresponding vertical drift velocity. Bubble occurrence is generally correlated with upward drift, which lifts the F‐layer and creates favorable conditions for bubble development. An exception is observed in the Asian sector during June, where weakened downward drifts likely promote post‐midnight bubble generation. High pre‐midnight occurrences occur in the American and African sectors during equinoxes under both low and high solar activity, consistent with alignment of the sunset terminator and magnetic meridian. During low solar activity, the presence of post‐midnight bubbles in the Pacific and Asian sectors without pre‐midnight activity suggests possible local generation. A key finding is the local‐time variations in bubble occurrence rates, suggesting different evolution mechanisms between low and high solar activity. During high solar activity, rates exhibit a rise‐and‐decay pattern, peaking in the pre‐midnight sector, consistent with rapid post‐sunset generation. In contrast, during low solar activity, rates gradually increase into the post‐midnight sector, implying a combination of drifting fossil remnants and locally generated bubbles. Overall, while largely consistent with established climatological features, our results provide new insight into the solar activity dependence of bubble evolution in the topside ionosphere.
Chen et al. (Mon,) studied this question.