Extremely Long-Range Observations of Ionospheric Irregularities in a Large Longitude Zone From Pacific to Africa Using a Low Latitude Over-The-Horizon Radar in China

Monitoring the generation and movement of equatorial plasma bubbles (EPBs) in a large longitude region is crucial important for better understanding their day-to-day variability. Using the newly developed Low lAtitude long Range Ionospheric raDar (LARID) at Dongfang (19.2 degrees N, 108.8 degrees E, dip lat. 13.8 degrees N), China, an extremely long-range experiment for observing EPB irregularities in a range of +/- 9,600 km to the radar site was first carried out. The results show that EPB irregularities with ranges up to 7,000 and 9,500 km were observed by the east and west beams of LARID, respectively. By incorporating simultaneous observations from GNSS receiver and ionosonde networks, it is demonstrated that the EPBs generated from post-sunset to sunrise over a very wide longitude of similar to 140 degrees, from Pacific to Africa could be observed by LARID. The results, for the first time, demonstrate the possibility for tracing global EPBs in real time using a few low latitude over-the-horizon radars. Equatorial plasma bubble (EPB), which can cause severe ionospheric scintillation, is an important space weather phenomenon. The occurrence of EPBs exhibits complex longitude variation characteristics. Due to the fact that most of the equatorial and low latitude region is covered by ocean, it is challenging to monitor the generation and movement of global EPBs. Recently, an over-the-horizon (OTH) radar at low latitude, that is, the LARID, has been built for observing EPB irregularities. However, it is not clear that how far an OTH radar at low latitude can observe irregularities. This would be very important in the design of a low latitude OTH radar network for tracing global EPB irregularities. To address this issue, an extremely long-range experiment covering a wide longitude of about 180 degrees was performed for the first time with LARID. The successful observation of EPB irregularities from Pacific to Africa sectors demonstrates the possibility of monitoring the complex longitudinal variations of EPBs by an OTH radar, even during geomagnetic storms. The results provide meaningful insight for building a low latitude OTH radar network in future, that consists of three to four OTH radars could have the capability to obtain global EPBs in real time. First extremely long-range experiment for observing equatorial plasma bubbles over a large longitude was conducted Equatorial plasma bubbles with ranges as far as 9,500 km were successfully observed by an over-the-horizon radar The results demonstrate the capability for tracing global equatorial plasma bubbles using a few low latitude over-the-horizon radars