Influences on the Development of Equatorial Plasma Bubbles: Insights from a Long-Term Optical Dataset
We present an analysis of an eight-year dataset of field-aligned optical images of the low-latitude, nighttime ionosphere. The duration of this dataset allows us to study the climatology of ionospheric structures, such as equatorial plasma bubbles (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs) during both high and low solar activity. In this chapter, we concentrate on the climatology of EPBs during both high and low solar activity and a possible linkage between EPBs and MSTIDs during low solar activity. In contrast to climatologies derived from forward-scattering (scintillation) measurement techniques and satellite-based in-situ measurements, we do not find a reduction in the occurrence of EPBs at low solar activities. However, we do find that EPBs typically occur later in the evening at low solar activity levels. We also present statistics for the occurrence of MSTIDs seen to the south of Hawaii during low solar activity, which indicate that the increase in post-midnight, quiet-time EPB occurrence during low solar activity is accompanied by an increase in MSTID occurrence.
KeywordsOccurrence Rate Ionospheric Disturbance Magnetic Equator Vertical Drift Solar Activity Level
Airglow observations on Mount Haleakala are supported by the Air Force Office of Scientific Research under Contract FA9550-05-0160494 to Cornell University. The continued operation of the instrument would not be possible without the continued on-site support of Jacob Burger. We thank Professor Michael C. Kelley for making the CNFI data available for our use. Work at the University of Illinois is supported by the National Science Foundation through grant ATM-06-044654. Ethan Miller acknowledges further support from a National Science Foundation CEDAR postdoctoral researcher award to JHU/APL.
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