Tracing the Origin of Daytime Ionospheric Topside Irregularities at Low Latitudes Using Radar and GNSS Receiver Observations

Abstract While most equatorial plasma bubbles (EPBs) dissipate before or around sunrise, some can persist into the daytime in the topside ionosphere. Using measurements from a phased array radar of the Meteor and ionospheric Irregularity Observation System (MIOS) and ground‐based Global Navigation Satellite System (GNSS) receivers, this paper presents cases of daytime ionospheric topside irregularities observed by the MIOS radar at low latitudes in China under both geomagnetic storm and quiet conditions. By using the rate of change of total electron content index from GNSS receivers combined with plasma zonal drifts from a model, the origins of these daytime ionospheric topside irregularities were successfully identified. The results show that the daytime ionospheric topside irregularities observed by the MIOS radar were the remnants of EPBs generated during post‐midnight or post‐sunset hours on the previous night. The daytime ionospheric topside irregularities originated from the nighttime EPBs initially generated at the same, western, or eastern longitudes of the radar site. One interesting finding is that EPBs were first detected by the MIOS radar during nighttime, and their remnants returned to the radar site during the daytime and were detected once again on some occasions.