ICON is focusing on a region of space between 60 and 300 miles above the Earth’s surface. This region is made up of a mix of atoms and molecules. Some of these are similar to the atoms and molecules we find in air near the surface; we call these “neutral” because they have no electric charge. However, some of these atoms and molecules have their electrons stripped away by ultraviolet radiation from the Sun. Since a is negative charge has been removed from these particles, they have excess positive charge, and therefore are no longer neutral. We call these ions. The region of space where these ions and free electrons coexist with the remaining neutrals is called the ionosphere - literally a sphere of ions.
The ions and electrons produced by solar ultraviolet radiation are not evenly distributed around the globe. In the regions near the equator, they are swept up into regions of enhanced density – where there are more ions per cubic meter than typical. These regions are strongly shaped by the interplay of magnetic fields, electric fields, the winds blowing in the upper atmosphere, and the electrical conductivity of the ionosphere. These regions of enhanced density come and go in very complicated ways, that we are just now able to observe in detail, but cannot yet predict.
A major driver of this variability is thought to be weather patterns in the troposphere and stratosphere, revealing a new set of connections in our extended atmosphere. ICON will probe the variations in the winds, conductivity, and electric field to determine, for the first time, what causes variations in the density of the ionospheric plasma near the equator.
Until recently, scientists thought that the Sun was the only thing influencing the ionosphere. However, recent discoveries suggest that the weather we experience at the surface of the Earth drives changes all the way out to the edge of space. This is a fundamental aspect of our planet, and probably other planets, that ICON will help us understand. In addition to being a mission of discovery, ICON will help us learn to predict what drives “patchiness” in the ionospheric plasma, with impacts on communication and navigation systems such as GPS.