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In this paper, we consider the fractional boundary value problemwhere D a 0+ is the standard Riemann-Liouville fractional derivative. By means of fixed point theorems, sufficient conditions are obtained that guarantee the existence of solutions to the above boundary value problem. The fractional modeling is a generalization of the classical integer-order differential equations and it is a very important tool for modeling the anomalous dynamics of numerous processes involving complex systems found in many diverse fields of science and engineering.

An Ionospheric Observational Network for Irregularity and Scintillation in East and Southeast Asia (IONISE) is developed to identify and study the short‐term and fine‐scale ionospheric variations over China. The IONISE network mainly includes three crossed chains of Beidou geostationary satellite total electron content (TEC)/scintillation receivers along 110°E, 23°N, and 40°N respectively, multistatic portable digital ionosondes and bistatic very high‐frequency radars. Based on the IONISE observations, we report some preliminary results of ionospheric disturbances and irregularities, including (1) initially generated and zonally drifting equatorial plasma bubbles and related scintillations, (2) traveling ionospheric disturbances from middle to low latitudes, (3) drift of strong sporadic E structures over a wide area of more than 1,000 km, (4) fine‐scale ionospheric perturbation and regional TEC gradient, and (5) general features of ionospheric response to geomagnetic storms. Possible mechanisms responsible for these ionospheric phenomena are discussed. The IONISE provides new data set for investigation on ionospheric disturbances of various scales in a broad region with dense observations along specific latitude/longitude.

Ionospheric F-region irregularity backscatter plumes are commonly regarded as a nighttime phenomenon at equatorial and low latitudes. Using the Sanya (18.4°N, 109.6°E, dip lat. 12.8°N) VHF radar, F-region backscatter echoes were observed at daytime during 0700-1800 LT, with an unexpected high occurrence in June solstice of solar minimum. Radar interferometry and ICON satellite in situ results show that the daytime F-region echoes were from plume structures consisting of field-aligned irregularities. The daytime echoing structures appeared mostly above 350 km altitude, extending up to 650 km or more with apparent westward drifts at times. We surmise that the daytime F-region echoes were due to equatorial plasma bubble irregularities generated on the previous night around 100-125°E, where the irregularities could survive unexpectedly long time, beyond sunrise as vertically elongated fossil plumes. Under the ionospheric background dynamics, the fossil plumes could be elevated to high altitudes and drift zonally over Sanya. Plain Language Summary Equatorial plasma plumes, which are known as vertically elongated irregularity structures over the magnetic equator, have been widely accepted as being generated at nighttime. The plumes usually disappear before sunrise. At daytime, there are very few reported cases of F-region backscatter echoes. It is still not clear what caused the daytime echoes. During November 2016 to August 2020, the Sanya VHF radar was operated for observing F-region echoes at daytime. The observations show that the daytime F-region echoing structures could appear at any time during 0700-1800 LT, with a maximum occurrence around 0900 LT. Radar interferometry and ICON satellite in situ results reveal that these daytime echoes were from field-aligned irregularities, which are shown as plume structures in the topside ionosphere. It is suggested that the plume structures could be remnants of equatorial plasma bubble (EPB) irregularities generated on the previous night around 100-125°E. They rise to high altitudes and drift zonally together with background plasma, causing the daytime F-region backscattering structure over Sanya. Our results indicate that the EPBs could maintain their vertically elongated structures and meter-scale irregularities at F-region topside for much longer time than previously thought and have important implications for understanding their dynamics.

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