ICON Science Overview

The Ionospheric Connection Explorer (ICON) will be the newest addition to NASA’s fleet of Heliophysics satellites. Led by UC Berkeley, scientists and engineers around the world are coming together to make ICON a reality. 

The goal of the ICON mission is to understand the tug-of-war between Earth’s atmosphere and the space environment. In the “no man’s land” of the ionosphere, at altitudes above 50 miles, a continuous struggle between forcing by both the Sun and Earth’s weather systems drives extreme and unpredicted variability. ICON will investigate the forces at play in the near-space environment.

We've known for many years that the Sun has a significant effect on this region of the upper atmosphere. As the Earth rotates, a new portion of its atmosphere is exposed to solar ultraviolet radiation, which heats and partially ionizes the neutral atoms and molecules, creating the ionosphere. At night, when that portion of the atmosphere is not exposed to the Sun, this ionized gas, or “plasma” tends to recombine, dramatically reducing its density as it converts back to an electrically neutral state.   In between, near sunset, the low-latitude ionosphere is dominated by a “plasma fountain”, which results in a dramatic upwelling of ionized gas. This results in a sharp increase of the density of ionized gas in narrow bands on either side of the magnetic equator. Basic models of the ionosphere predict that there should be a regular rise and fall of this portion of the atmosphere as the Earth rotates from day to night, independent of longitude.

Left: The predicted distribution of plasma around the magnetic equator after sunset. Right: The observed distribution of plasma around the magnetic equator, made by NASA's TIMED Spacecraft. Notice the large, unexplained enhancements over the continents

However, recent observations call this overly simplistic picture into question. Other missions, such as NASA's TIMED spacecraft [link] have shown ionospheric plasma distributed in unexpected patterns across the globe, with apparent correlations with landmasses. You might expect this to be explained by variations in the Sun’s activity, which give rise to space weather or geomagnetic storms. Surprisingly, these variations are seen even when the Sun is very quiet, meaning that they are driven by other processes, which may include the more familiar weather we experience at ground level. 

Understanding what is causing the variations in the atmosphere is very important in the technological era we live in today. As a society, we are very dependent on communication and navigation networks around the globe – both space based, and ground based. We have also recently developed a strong reliance on broadcast navigation signals such as those provided by GPS satellites. The radio signals used for communication and navigation must propagate through the ionosphere, and non-uniform distributions of plasma in the ionosphere can act like bubbles in a lens or scratches in a mirror, distorting the signal, sometimes to the point of unintelligibility or unusability.

Understanding what drives variations in the ionosphere is important so that we can better predict what types of signal distortions we may expect and where, as well as ways to design systems that are more robust against these effects.

ICON skin is based on Greytness by Adammer
Background image, courtesy of NASA, is a derivitave of photograph taken by D. Pettit from the ISS, used under Creative Commons license