This project will design, fabricate, and deploy a longitudinal network of instruments along the magnetic equator in the Indo-Pacific region in order to facilitate investigations of day-to-day low-latitude ionospheric variability, particularly with regard to migrating and non-migrating tidal structures. Such measurements will be able to resolve space-time ambiguities in satellite observations of wave structures, and the project will determine whether such structures are produced as a standing wave pattern or by zonally propagating, non-migrating waves. Specifically, the instrumentation will include magnetometer pairs and radars capable of obtaining both 150 km and equatorial electroject echos. This project will build upon previously established international collaboration and foster new partnerships with international investigators.
Normal 0 false false false EN-US X-NONE X-NONE The charged-particle distribution in the low-latitude ionosphere is usually smooth and laminar during the day, but can become irregular and structured at night. When, where, and how irregularities develop are of considerable interest from a basic-physics point of view. Moreover, this knowledge has important practical applications in space weather as a means for forecasting the deleterious effects of irregularities on communications and navigation. Climatologically, irregularity-generation appears to be controlled largely by solar-driven tidal effects produced by the motion of the Earth’s atmosphere. Because of their synchronized movement with the Sun, the source is referred to as a migrating tide. Recent research has shown, however, that there are other sources of neutral gas motion that are associated with land-sea and orographic effects; these are referred to as non-migrating tides. Irregularity generation on shorter time scales, in particular, its day-to-day variability, is further complicated by the presence of other wavelike behavior in the Earth’s atmosphere, including the so-called planetary waves on larger spatial scales and atmospheric gravity waves (AGWs) on smaller scales. The objective of this project was to gain further insight into the space-time effects of neutral dynamics on irregularity generation, from climatological behavior to their day-to-day variability. The basic approach was to collect information about the ionospheric irregularities as a function of time, from several observing stations that are distributed in longitude, in the vicinity of the magnetic equator. Most useful were the measurements of total electron content and radio scintillations, where were obtained using dual-frequency radio transmissions from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Because C/NOFS is in an equatorial orbit, high-resolution measurements could be made as a function of longitude in the vicinity of each observing station, and globally through the use of widely spaced stations. The focus of this three-year study was to assess the development of regions of locally-depleted plasma, called equatorial plasma bubbles (EPBs), shortly after sunset, on a day-to-day basis. The development of EPBs was shown to be closely associated, climatologically, with the rise of the ionosphere, produced by both migrating and non-migrating tides. On shorter time scales, the development of EPBs was shown to be influenced by smaller perturbations associated with AGWs. Three papers, reporting these results, have been published in peer-reviewed journals. A fourth paper, reporting the most recent results, has been submitted for publication in a peer-reviewed journal. The data collected will be made available to interested researchers, upon request. The project has provided opportunities to researchers and students.
