We know from earlier flight projects that light atoms [and ions] flow upward into low pressure regions at high altitudes, much as the solar wind flows away from the sun. Also, we know that a planetary-scale fountain of heavy ions exists in the noon sector auroral oval, spewing an average of 50 tons of plasma per day up out of the gravitational pull of Earth. In fact, this is the most prolific "leak" of atmospheric mass from the Earth.

The plasma fountain was discovered using data from the Retarding Ion Mass Spectrometer on the Dynamics Explorer spacecraft, in the 1980's. Recently, the SCIFER sounding rocket was launched into the plasma heating region of the fountain [as illustrated in the figure] to better understand how this fountain is generated. Initial results may be found in Geophysical Research Letters, 1 July 96 issue.