Visualizations by
Tom Bridgman
Released on November 29, 2021
As one rises through the turbulent atmosphere of Earth, the density of the air decreases and winds become faster. From above, solar radiation as visible and ultraviolet light, along with energetic particles, rain down on the atmospheric gases splitting electrically neutral atoms and molecules into ions and free electrons. This process forms the high-altitude atmospheric region we call the ionosphere. The charged particles formed here interact with Earth's magnetic field to form more complex structures, such as equatorial ionization anomaly (EIA) also known as the Appleton anomaly formed by a process called the equatorial fountain. These interactions drive a process called the ionospheric dynamo.
But these high-altitude winds are not uniform. They are often altered by weather changes in the lower-altitude atmosphere, and this can drive changes in the particle motion high in the ionosphere.
The ICON satellite has instruments that measure charged particle motion though the region it travels (Ion Velocity Meter or IVM), and also winds on the limb of Earth (measured by MIGHTI). Sometimes these two regions are connected by a magnetic field line and we can actually 'see' how a change in lower altitude winds can drive a change in the high altitude charged particle motions. In the visualizations above, this process takes place between the 01:52 and 01:56 timestamp, highlighted with yellow magnetic field lines. We see the wind speed (green arrows on the left) change direction and switch the charged particle flow measured at the spacecraft (red arrows) from upward to downward.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0