Instrument-Cluster Studies of Equatorial Spread F

Sri International, Menlo Park CA

Investigators

Abstract

The investigators will study the cause of the day-to-day variability in the development of plasma structure in the equatorial layer referred to as equatorial spread (ESF). The study will be based on the hypothesis that ESF originates from large-scale wave structure (LSWS). LSWS is an altitude modulation of isodensity contours in the bottomside layer that grows to large amplitudes. The modulation alters the background conditions that control development of ESF and features such as equatorial plasma bubbles (EPBs), a behavior that is of considerable interest to space weather. LSWS has been ignored almost completely by researchers for good reasons. Experimentalists have been unaware of its existence, and theorists have not considered it because its importance remained questionable. However, recent observations have shown that LSWS is real, occurs frequently in the evening equatorial layer, and appears to play a substantial role in the day-to-day variability of ESF and EPBs. The objectives of the study are twofold: (1) to extract as much information as possible about LSWS from well-designed experiments, data analysis, and theoretical studies, and (2) to investigate the day-to-day variability problem through a series of tasks that can test the working hypotheses. New paradigms will be constructed following those tests, and that cycle will be repeated throughout the course of the project. The studies will revolve around the analyses of unique databases and new experiments that will take advantage of a unique cluster of instruments, which is capable of extracting the properties of LSWS. The cluster is unique because it can distinguish spatial from temporal variations, and LSWS is essentially a stationary spatial structure during its growth phase. The goal of the project is to obtain a comprehensive description of LSWS, and derive considerable insight about seeding, LSWS amplification, and the development of EPBs. The results will also validate the crucial need for instrument clusters in studies of ESF.