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The characteristics of winter nighttime enhancement (WNE) of the midlatitude ionosphere at 300, 550, and 750 km altitude are presented, based on the radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate. WNE at 750 km altitude has earlier start time and larger increasing rate than that at 550 km, possibly due to the downward plasma diffusion from above that dominates the most upper part of the ionosphere. Theoretical calculation of the plasma transport at 300 km altitude reveals the largest effect of downward diffusion at 45° geomagnetic latitude, consistent with the latitudinal distribution of WNE. Meanwhile, the wind‐driven plasma transport also contributes to WNE, at 30°W–180°W geographic longitude in the Southern Hemisphere. The strength and end time of WNE vary with longitude, and are correlated with the longitudinal variations of the enhancement in the conjugate (summer) hemisphere. This may be attributed to the transport processes in the interhemispheric geomagnetic flux tubes, which redistribute and balance the plasma between the conjugate hemispheres at night. The plasma flux from above is hence an important plasma source for further understanding of both the winter and summer nighttime enhancements. Key Points: Stronger winter nighttime enhancement with earlier start time is observed at 750 km than at 550 km altitudeThe downward diffusive flux dominates the formation of the enhancement, while the neutral wind also contributes at certain longitudesThe plasma flux from above could be an important plasma source for both the winter and summer nighttime enhancements [ABSTRACT FROM AUTHOR]

The article used the possibility-satisfaction degree method of system engineering to build a forecasting model of the reasonable population scope in Shanghai city. It incorporates lots of factors in five aspects that are the level of economics, social living, level of resources, environments and strength requirement and finds the reasonable population scope and the conditions that the scope relies on at an objective time. The article made different kinds of acuity degree analysis of key influence factors and got some policy conclusion. It has a certain theoretical value and practical meaning for implementing the object of reasonable population scope. [ABSTRACT FROM AUTHOR]