Robert F. Pfaff
Goddard Space Flight Center
Electric Field and Plasma Density Measurements of theTurbulent Low and Mid-Latitude Ionosphere
The Earth’s ionosphere at low and mid-latitudes is know to become unstable after sunset, exhibiting depleted, dynamic flux tubes and associated waves and turbulence. Such “convective storms” which are typically called “Spread-F” are inherently non-linear, highly variable, difficult to predict, and among the major causes of radio wave communication and navigation disruptions in the low latitude ionosphere. In situ measurements of DC and AC electric fields, plasma density, and magnetic fields provide direct information concerning both the driving electrodynamics and the resulting irregularities that are inherent to equatorial Spread-F. We provide recent electric field and plasma density observations of mid- and low-latitude ionospheric structures and turbulence associated with geomagnetic storms observed with instruments on the polar-orbiting DEMETER satellite. Future equatorial-orbiting missions, such as the Air Force Communications/Navigation Outage System (C/NOFS) satellite, will provide continuous, multi-instrument measurements of all of the critical parameters believed to drive and sustain such ionospheric turbulence. When coupled with advances in modeling, theory, ground-based measurements, and high level analysis, these new data promise to significantly advance our understanding of this major space weather problem. This presentation reviews the scientific motivation for gathering in situ DC and AC electric field measurements on space flight missions designed to study mid- and low-latitude ionospheric turbulence and convective storms.