In this study, multiple data sets from Beidou geostationary orbit satellites total electron contents (TECs), ionosonde, meteor radar, magnetometer, and model simulations have been used to investigate the ionospheric responses in the Asian‐Australian sector during the September 2017 geomagnetic storm. It was found that long‐duration daytime TEC enhancements that lasted from 7 to 12 September 2017 were observed by the Beidou geostationary orbit satellite constellation. This is a unique event as the prominent TEC enhancements persisted during the storm recovery phase when geomagnetic activity became quiet. The Thermosphere‐Ionosphere Electrodynamics Global Circulation Model predicted that the TEC enhancements on 7–9 September were associated with the geomagnetic activity, but it showed significant electron density depletions on 10 and 11 September in contrast to the observed TEC enhancements. Our results suggested that the observed long‐duration TEC enhancements from 7 to 12 September are mainly associated with the interplay of ionospheric dynamics and electrodynamics. Nevertheless, the root causes for the observed TEC enhancements seen in the storm recovery phase are unknown and require further observations and model studies.

The understanding of the Earth's space environment has grown exponentially over the centuries since the step into space age (Jacchia, 1959). The so-called space weather, which describes the "weather" changes in solar-terrestrial connections, has shown broad influences in civilian life, commerce, and national security, including communication, navigation, electric grids and satellite operations (

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A composite time series of the merged satellite altimeters sea surface height anomaly (SSHA) data and satellite-observed sea surface temperature (SST) data were used to identify eddies in the Western North Pacific Ocean (WNPO), where there were numbers of intense typhoons. This study systematically investigated 15 super typhoons during the period of 2000-2008 in the WNPO to study their impacts on the pre-typhoon ocean features, e.g., the cyclonic ocean eddy (COE) feature (closed contours of SSHA < 26 cm) and neutral condition (SSHA between 26 and 6 cm). Two new COEs are generated by two super typhoons, and 18 pre-existing COEs are intensified by 13 super typhoons. 5 of the 13 super typhoons each influenced two pre-exisiting COEs. Although the typhoon-induced maximum cooling centers had a right bias along the tracks due to wind conditions, pre-existing COEs also play a significant role in determining the strength and location of large SST cooling. Three possible factors (maximum wind speed, typhoon translation speed and the typhoon forcing time, T f ) are employed to explain the interactions. Above all, the changes of the COE geometric and physical parameters (e.g., effective radius, area, SST, SSHA, and eddy kinetic energy) were mostly related to the typhoon forcing time, T f . This is because T f is a parameter that is a combination of the typhoon's translation speed, intensity and size. Although the typhoons may significantly impact COEs, such samples were not commonly observed. Thus, the impact of typhoon on the strength of COEs is generally inefficient.