fringe region

The upper portion of the exosphere, where the cone of escape equals or exceeds 180ø; in this region the individual atoms have so little chance of collision that they essentially travel in free orbits, subject to the earth’s gravitation, at speeds imparted by the last collision. Also known as spray region.

Related terms:

• air-mass source region
• source region
• F region
• spray region
• delta region
• D region
• entrance region
• hyetal region
• auroral region
• exit region