ICON Snaps a Peek at the Ionospheric Dynamo

GIFLaunched in 2019, ICON, short for Ionospheric Connection Explorer, is a mission to untangle how Earth’s weather interacts with the weather in space. Radio and GPS signals zip through the ionosphere, which is home to auroras and the International Space Station. Empty pockets or dense swells of electrically charged particles can disrupt these signals.Credit: NASA GIFIn the ionosphere, high-altitude winds tend to push on chunky, charged particles more than small, negatively charged electrons. This separation between ions and electrons creates an electric field in the dynamo region, near the bottom of the ionosphere.Credit: NASA's Conceptual Animation Lab GIFOne source of atmospheric tides is created above rainforest regions around Earth’s equator such as the Amazon rainforest. In this region, daily cycles of cloud formation put energy into the atmosphere that, in turn, create a daily cycle of heating and cooling. The heating and cooling pushes wind patterns out and towards regions where clouds are forming. These winds eventually form an atmospheric tide that propagates up through the atmosphere.Credit: NASA's Conceptual Animation Lab GIFAtmospheric tides created by rainforests form a tidal pattern with three main peaks that span and move across the globe as Earth rotates.Credit: NASA's Conceptual Animation Lab GIFAt 60-95 miles above the ground, winds associated with atmospheric tides (white arrows) move ions and separate them from electrons, forming an electric field (blue line) in the dynamo region. The electric field permeates through the upper atmosphere and pushes plasma (pink) upwards and downwards like a fountain at 370 miles above Earth’s surface.Credit: NASA's Conceptual Animation Lab ANIMATIONOne source of atmospheric tides is created above rainforest regions around Earth’s equator such as the Amazon rainforest. In this region, daily cycles of cloud formation put energy into the atmosphere that, in turn, create a daily cycle of heating and cooling.The heating and cooling pushes wind patterns out and towards regions where clouds are forming. These winds eventually form an atmospheric tide that propagates up through the atmosphere.At 60-95 miles above the ground, winds associated with atmospheric tides (white arrows) move the chunky, charged ions and separate them from the small, negatively charged electrons, forming an electric field (blue line) in the dynamo region, near the bottom of the ionosphere.The electric field permeates through the upper atmosphere and pushes plasma (pink) upwards and downwards like a fountain at 370 miles above Earth’s surface.Credit: NASA's Conceptual Animation Lab InfographicCredit: NASA/Mary P. Hrybyk-Keith Using observations from NASA’s ICON mission, scientists presented the first direct measurements of Earth’s long-theorized dynamo on the edge of space: a wind-driven electrical generator that spans the globe 60-plus miles above our heads. The dynamo churns in the ionosphere, the electrically charged boundary between Earth and space. It’s powered by tidal winds in the upper atmosphere that are faster than most hurricanes and rise from the lower atmosphere, creating an electrical environment that can affect satellites and technology on Earth. The new work, published today in Nature Geoscience, improves our understanding of the ionosphere, which helps scientists better predict space weather and protect our technology from its effects.More information: https://www.nasa.gov/feature/goddard/2021/strong-winds-power-electric-fields-in-upper-atmosphere-icon/ For More InformationSee [https://www.nasa.gov/feature/goddard/2021/strong-winds-power-electric-fields-in-upper-atmosphere-icon/](https://www.nasa.gov/feature/goddard/2021/strong-winds-power-electric-fields-in-upper-atmosphere-icon/) Related pages

Visualization illustrating the Fountain Effect of ions in the near-Earth electric and magnetic fields. Color bar for oxygen ion density. This is a visualization of the Equatorial Fountain process in the ionosphere, whereby ions are driven away from the equator forming ion density enhancements to the north and south of the equator. This visualization is depicted near 50 degrees west longitude, where the magnetic equator crosses the geographic equator. Magnetic field lines near Earth are represented by the gold lines. Particles appear in a blue-white flash, representing the point where atoms are ionized, becoming positively charged and releasing an electron. Now these charged particles can 'feel' the near-Earth electric and magnetic fields. Their motion becomes a combination of circular gyromotion (see Plasma Zoo: Gyromotion in Three Dimensions) due to the magnetic field and E-cross-B drift (see Plasma Zoo: E-cross-B Drift). At higher altitudes, the electric field is weaker, reducing the vertical motion, and the ion motion becomes dominated by the magnetic field and gravity, allowing the ion to 'slide' down the magnetic field line back to Earth. At lower altitudes, the ions combine with free electrons in a process called recombination, represented by a red flash and fading of the particle trail. A slice of data from the IRI (International Reference Ionosphere) model represents the density of singly-ionized oxygen atoms is faded-in to compare to the particle motion. Red represents high ion density, green represents low ion density. The camera finally pulls out from Earth, providing an overview of the enhanced ion density (red) above and below the magnetic equator on the dayside of Earth. This enhancement was discovered by Edward Appleton in 1946.The Fountain effect is just one of the many of complex processes which occur in the layer of thinning atmosphere that forms Earth's interface to the space environment. A conceptual inventory of some of these processes are presented in the graphic at Terrestrial Atmosphere ITM Processes.What creates the dayside near-Earth electric field? As the sun warms Earth's atmosphere during the day, the temperature and pressure differences create wind flows. In the upper atmosphere, where the solar ultraviolet photons also break atoms into negative-charged electrons and positive-charged ions, these winds carry the charges creating currents and electric fields. The major current from this process is called the equatorial electrojet and travels along the magnetic equator (not quite aligned with the geographic equator). This motion of charges also creates a west-to-east directed electric field.Are the particles in this visualization at a realistic scale? The particles in this visualization are generated to be representative of the motion in the fountain effect to the appropriate altitudes and latitudes, but items such as the size of the gyromotion, and the particle size, are not to be regarded as physically accurate. ReferencesNOAA/National Geophysical Data Center. International Geomagnetic Reference FieldErwan Thebault, Christopher C. Finlay, et al. International Geomagnetic Reference Field: the 12th generation. Earth, Planets and Space 67:79 (2015)Dieter Bilitza. The International Reference Ionosphere - Status 2013. Advances in Space Research, Volume 55, p. 1914-1927 (2015)Douglas P. Drob, John T. Emmert, et al. An update to the Horizontal Wind Model (HWM): The quiet time thermosphere. Earth and Space Science, vol. 2, issue 7, pp. 301-319Edward V. Appleton. Two Anomalies in the Ionosphere. Nature, Volume 157, pp. 691 (1946)E. N. Bramley and M. Peart. Diffusion and electromagnetic drift in the equatorial F2-region. Journal of Atmospheric and Terrestrial Physics, vol. 27, pp. 1201-1211 (1965)R.J. Moffett & W.B. Hanson. Effect of Ionization Transport on the Equatorial F-Region. Nature 206, pp705-706 (1965) Related pages

ICON orbits Earth at 575 kilometers altitude, measuring the composition and motions of the ionosphere. The ICON (Ionospheric Connection Explorer) satellite orbits Earth at an altitude of 575 kilometers. In this visualization, we show the ICON spacecraft with the fields-of-view of four instruments for measuring the properties of the ionosphere. ICON has an EUV (Extreme Ultraviolet) and FUV (Far Ultraviolet) imagers (violet colored frustrums directed from spacecraft) pointing perpendicular to the orbit direction for detecting ionospheric emissions. Two Doppler interferometer imagers, MIGHTI (Michelson Interferometer for Global High-resolution Thermospheric Imaging), represented by the blue frustrums, are directed at 45 degrees from the EUV and FUV imagers to measure ionospheric wind velocities.Three reference models important in ionospheric physics are presented in this visualization. One of the goals of ICON is to improve on these models.International Reference Ionosphere (IRI)This model provides parameters such as electron temperature and density, ion temperature and the densities of various ions (O+, H+, He+, NO+, O2+). In this visualization, we display the atomic oxygen positive ion (a single atom ion) density at an altitude of 350 kilometers. On the limb of Earth, we present a vertical cross-section of the model, illustrating how the density varies with altitude and providing an altitude scale for comparison. This dataset exhibits two notable characteristics.Daily variation: The oxygen ion density increases during the day and then decreases after nightfall. This is due to photoionization by solar ultraviolet light, which increases with sunrise to a maximum at local noon, and then decreases towards evening.Appleton Anomaly: One of the more striking features of the ion density is the daytime enhancement is split into two regions, distributed symmetrically above and below the magnetic equator. This feature was discovered by Edward Appleton in 1946. It is now understood to be an effect of the interaction of Earth's geomagnetic field with upper atmosphere electric fields, and often referred to as the 'fountain effect,' explained in 1965. The electric fields lift ions and electrons upward by E-cross-B drift (Plasma Zoo). At higher altitudes, the upward drift decreases and the geomagnetic field and gravity dominate the motion, guiding the charged particles earthward.Horizontal Wind Model (HWM)This model provides speed and direction of horizontal (parallel to Earth's surface) winds constructed from over 70 million ground-based and satellite measurements. Two altitude levels are displayed in this visualization: 350 kilometers (same altitude as the IRI oxygen ion data) in violet glyphs, and 100 kilometers (white glyphs). This model only extends to 60 degrees latitude, so there are gaps around the poles in this visualization.One of the most notable characteristics in this dataset, particularly the 350 kilometer data, is how the winds are driven by the daily solar heating cycle. As the sun rises, the upper atmosphere is heated by solar ultraviolet light. This creates a high-pressure region which drives the atmosphere away from direct sunlight; westward in the morning and eastward in the afternoon. As the sun sets and the atmosphere cools, we see the wind reverse, filling in the now cooler and lower-pressure region.International Geomagnetic Reference Field-12 (IGRF-12)This model provides the structure of Earth's magnetic field which is a dominant influence on the motion of electrons and ions in the ionosphere. The geomagnetic field changes very slowly over decades. For this visualization, we display only a few field lines (golden wire-like structures) near the geomagnetic equator. As we observe the daily variation of the data, particularly the oxygen ions, we see the Appleton anomaly is hedged in by the low-latitude geomagnetic field.ReferencesNOAA/National Geophysical Data Center. International Geomagnetic Reference FieldErwan Thebault, Christopher C. Finlay, et al. International Geomagnetic Reference Field: the 12th generation. Earth, Planets and Space 67:79 (2015)Dieter Bilitza. The International Reference Ionosphere - Status 2013. Advances in Space Research, Volume 55, p. 1914-1927 (2015)Douglas P. Drob, John T. Emmert, et al. An update to the Horizontal Wind Model (HWM): The quiet time thermosphere. Earth and Space Science, vol. 2, issue 7, pp. 301-319Edward V. Appleton. Two Anomalies in the Ionosphere. Nature, Volume 157, pp. 691 (1946)E. N. Bramley and M. Peart. Diffusion and electromagnetic drift in the equatorial F2-region. Journal of Atmospheric and Terrestrial Physics, vol. 27, pp. 1201-1211 (1965)R.J. Moffett & W.B. Hanson. Effect of Ionization Transport on the Equatorial F-Region. Nature 206, pp705-706 (1965) Related pages