Global-scale Observations of the Equatorial Ionization Anomaly

Monday, August 5, 2019

The NASA Global-scale Observations of the Limb and Disk (GOLD) ultraviolet spectrograph began imaging the Equatorial Ionization Anomaly (EIA), regions of the ionosphere with enhanced electron density north and south of the magnetic equator, in October 2018. The initial three months of observations were during solar minimum conditions, and they included observations in December solstice of unanticipated variability and depleted regions.

GOLD image of the daytime airglow and the equatorial ionization anomaly
GOLD image of the daytime airglow and the equatorial ionization anomaly (EIA): The image shows the 135.6 nm emission of atomic oxygen on October 15, 2018. The data are from a 24 minute scan began at 22:10 UT (19:00 at the subsatellite location, on the equator at 47.5 deg. West longitude). Continental outlines, a 15° latitude-longitude grid, and the location of the magnetic equator have been added to the image. A logarithmic scale is used in order to identify the faint nighttime and twilight emissions. The left side of the Earth is sunlit, but the Sun has already set over most of South America, and the transition from day to night is near the East coast of North America. The EIA appears as two arcs on either side of the magnetic equator, extending across the nightside. The aurora can be seen on the horizon at the top and bottom of the Earth.

These depleted regions are important because they are associated with the plasma instabilities, ionospheric scintillations, or “spread-F” that can cause disruptions in communications and satellite navigation. Depletions are seen on most nights, in contrast to expectations from previous space-based observations. The variety of scales and morphologies also pose challenges to understanding of the EIA. Abrupt changes in the EIA location, which could be related to in situ measurements of large-scale depletion regions, are observed on some nights. Such synoptic-scale disruptions have not been previously identified.

The observations are described in an paper by GOLD Principal Investigator Richard Eastes, The University of Colorado Laboratory for Atmospheric and Space Physics, which has been accepted for publication in Geophysical Research Letters.

Link to Article

Publication Name: Geophysical Research Letters
First HAO Author's Name: Stanley C. Solomon