Comparing Atomic Oxygen Emission Observed by GOLD with Ionospheric Total Electron Content (TEC)

Related pages

• Related

  • 

    Observing Earth's Ionosphere with GOLD

    July 17th, 2019

    A visualization of GOLD data observing Earth's ionosphere in ultraviolet light around the wavelength of an atomic oxygen emission. A visualization of GOLD data observing Earth's ionosphere in ultraviolet light also indicating the structure of the low-latitude geomagnetic field (gold curves). Color bar for GOLD radiance values near oxygen emission line. This is a visualization of data taken by the GOLD spectrometer aboard the SES-14 satellite. SES 14 is positioned in a geostationary orbit above 47.5 degrees west longitude so it always observes the same hemisphere. This data is of ultraviolet emission from Earth's ionosphere in a band near the wavelength of 135.6 nanometers, an emission line of atomic oxygen.This data is presented with a spectral color table, where red is the bright and violet is dim. We see some this emission in the aurora (visible at the north and south polar regions), energized by electrons and ions streaming in from Earth's magnetic field. More emission is created during the day by sunlight pumping atomic oxygen into an energetic state. As the sun sets, the oxygen decays from the energized state, releasing a photon of ultraviolet light. We see more emission from two bands near the equator after sunset. This double-lobed enhancement straddles the magnetic equator which is offset around the geographic equator, especially over South America. This enhancement corresponds to the Appleton anomaly, originally discovered in 1946. In the version showing the geomagnetic field, it is easy to see how the field channels the excited atoms. See also Interface to Space: The Equatorial Fountain.GOLD is a scanning instrument that alternates between scanning the northern hemisphere, and then the southern hemisphere (other scanning modes are possible, but not included in this visualization). The full-disk images shown here are created by combining these two hemisphere scans. The time difference between the scans creates a discontinuity at the equator which is particularly visible at the day-night terminator when these scans are combined for full-disk imaging. Differences between the north-south scan interval and south-north interval makes changes in this edge.Between about 22:00 UT and 06:00UT the next day, there is a large data gap because the Sun would appear behind the Earth from the position of GOLD and potentially shine directly into the GOLD instrument. For More InformationSee [NASA Mission Page](https://www.nasa.gov/content/goddard/gold) Related pages

    Read more
  • 

    Interface to Space: The Equatorial Fountain

    Jan. 31st, 2018

    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

    Read more
  • 

    Exploring Earth's Ionosphere: Limb view

    Jan. 13th, 2017

    This visualization presents data on the concentration of the singly-ionized oxygen atom (rainbow color table, red is highest concentration), the low-latitude geomagnetic field (gold field lines) and the ionospheric winds at two altitude levels, 100km (white) and 350 km (violet). This visualization presents data on the concentration of the singly-ionized oxygen atom at 350km altitude (rainbow color table, red is highest concentration) and the ionospheric winds at two altitude levels, 100km (white) and 350 km (violet). This visualization presents data on the concentration of the singly-ionized oxygen atom at 350km altitude (rainbow color table, red is highest concentration) and the low-latitude geomagnetic field (gold field lines). This visualization presents data on the concentration of the singly-ionized oxygen atom at 350km altitude (rainbow color table, red is highest concentration). Color bar of singly-ionized atomic oxygen density. Dynamic Planet format (4Kx2K). O+ion density at 350 km altitude. Versions with and without Dayside/Nightside mask. Data covers the time frame from January 19 @ 01 UT to January 25 @ 13 UT. Each frame is a time difference of 200 seconds, or 3 minutes 20 seconds. This visualization presents several 'Reference models' for studying Earth's ionosphere. It presents a close-up view of Earth's limb and ionospheric data-driven models, over a fixed geographic location - off the Atlantic coast of South America.Reference models are used to define well-established knowledge and facilitate mapping out areas for future exploration. The models might be described as semi-empirical, in that they are generated using many measurements at a varietly of locations, and those measurements are used to constrain a theoretical model which is used to estimate measurements at locations where an actual measurement is not available.Three models important in ionospheric physics are presented in this visualization.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

    Read more