Broad Plasma Decreases in the Equatorial Ionosphere
Journal article postprint
AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
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During June 2008 broad plasma density decreases BPDs were detected repeatedly by the Planar Langmuir Probe PLP on board the CommunicationsNavigation Outage Forecasting System CNOFS satellite. These density minima, not to be confused with Equatorial Plasma Bubbles EPBs, occurred within 15 degrees of the equator, consisted of reductions in plasma density up to an order of magnitude and extended across several degrees in azimuth along the orbit. Analysis revealed that the BPDs occurred nearly daily from May through July 2008 on CNOFS, and that the widest BPDs were observed in the vicinity of the South Atlantic Anomaly SAA. Similar BPDs simultaneous with the CNOFS measurements were observed by instruments on the CHAllenging Minisatellite Payload CHAMP and Defense Meteorological Program DMSP satellites. An examination of plasma densities revealed that these phenomena were a frequent occurrence during 1 the period around June solstices during 2 solar minimum years 3 in the vicinity of the SAA. Neutral densities were examined during periods when BPDs were detected, and at times there are simultaneous neutral depletions. One possible explanation is a decrease in temperature of both ions and neutrals in the equatorial region at these times, consistent with downwelling in the ionosphere and thermosphere. Measurements of plasma temperatures on DMSP support this hypothesis.
- Atmospheric Physics