The plasma fountain (or polar wind) in the Earth's atmosphere. The drawing shows bright yellow (next to the green colored area). That orange area is supposed to show ions (that come from gas in the atmosphere) that are escaping from the atmosphere (into space). The escape of those oxygen ions and hydrogen ions and helium ions, are part of the plasma fountaineffect. The atmosphere (including the ionosphere) near the North pole and South pole, goes higher above the surface of Earth, than in other places. The drawing shows the area near the North pole, and the plasma fountain. The drawing does not show the area near the South pole (and gas escaping from the atmosphere there).
In 2007, a research paper said that Plasma fountain (or Polar wind) is "an ambipolar outflow of thermal plasma from [the ionosphere near the North pole and South pole, or] high-latitude ionosphere"; That plasma moves from the ionosphere to the magnetosphere.
Decades of research have led to a body of scientific work; A thing that it says, is that there is at least one electric field on the outer limits (of the ionosphere).
The electric field gets called different things, such as
polarization field (and polarization electric field)
ambipolar field (and ambipolar electric field)
Causes of the plasma fountain (or polar wind)
About 30 years of research [as of the 2020s], says that the cause of the plasma fountain (or polar wind) is ambipolar outflow of thermal plasma: ion acceleration by a polarization electric field at high altitudes.:451
The polarization electric field or ambipolar electric field was originally proposed in the 1920s for ionized stellar atmospheres.:1927
The field is very small but, unlike other forces, it points away from gravity.:1927 In low-density plasma at high altitude (above Earth), it overwhelms gravity for light ions.
↑Schunk, R. W.; Nagy, Andrew (2000). Ionospheres: physics, plasma physics, and chemistry. Cambridge atmospheric and space science series. New York: Cambridge University Press. ISBN978-0-521-63237-9.