Editing Exosphere (section)

===Upper boundary===
[[File:IBEX ENA Feature FInal Fig3.jpg|thumb|Earth's exosphere, [[energetic neutral atoms]] (ENA) and [[magnetosphere]].]]
In principle, the exosphere covers distances where particles are still [[Gravity|gravitationally]] bound to [[Earth]], i.e. particles still have ballistic orbits that will take them back towards Earth. The upper boundary of the exosphere can be defined as the distance at which the influence of solar [[radiation pressure]] on atomic [[hydrogen]] exceeds that of Earth's gravitational pull. This happens at half the distance to the Moon or somewhere in the neighborhood of {{convert|200,000|km}}. The exosphere, observable from space as the [[geocorona]], is seen to extend to at least {{convert|100,000|km}} from Earth's surface.<ref>{{cite web| url=https://scied.ucar.edu/learning-zone/atmosphere/exosphere#:~:text=Since%20the%20exosphere%20gradually%20fades,about%20halfway%20to%20the%20Moon.|title=The Exosphere|website=University Corporation for Atmospheric Research|access-date=October 5, 2022}}</ref>