资源环境科技发展态势分析平台

The Communication/Navigation Outage Forecasting System satellite was operational from 2008, a period of deep solar minimum, to 2015, a period of moderate solar conditions. The behavior of the vertical plasma drift and the distribution of plasma depletions during the deep solar minimum of 2009 deviated substantially from the behavior that was observed during the solar moderate conditions encountered by the Communication/Navigation Outage Forecasting System satellite in 2014, which are typical of previous observations. Presented here are observations of the vertical drift of plasma depletions and the background plasma in which they are embedded. We find that depletions detected at local times after 2100 hr during solar minimum are typically found in background drifts that are weakly downward compared to the strongly downward background drifts observed during moderate solar activity levels. Additionally, at solar minimum, the drift within the depletions is upward with respect to the background as compared with observations at the same local times during solar moderate conditions for which the depleted plasma more nearly drifts with the background. We note that weak background plasma drifts observed throughout the night during solar minimum promote the continued growth of depletions that may evolve more slowly or be continuously generated to appear in the topside in the postmidnight hours.

Plain Language Summary The generation of equatorial ionospheric irregularities represents a fundamental plasma process of interest to a broad spectrum of plasma physicists. Interest in the Earth's ionosphere particularly broad and currently active because the evolution of conditions that give rise to the growth of plasma structures is not well understood. In particular many studies of the ionosphere under the recent solar minimum conditions have shown that equatorial plasma structures do not behave in the same way as those seen at more moderate solar activity levels. Various studies have shown that the large-scale dynamics of the ionosphere has a strong influence on the evolution of plasma structures. This work reports on the average properties of the underlying background dynamics of the equatorial ionosphere that exists in the absence and presence of plasma structure. Such information can be broadly utilized to reevaluate instability growth rates as they apply to a variety of different observational conditions. The behavior of ionosphere under very low solar activity levels has been unique and provides opportunities for new insights into the dynamic ionosphere in which irregularities are formed.