In May 2024, during a period of intense solar activity, the Sun hurled seven coronal mass ejections towards Earth, culminating in an extreme geomagnetic storm on May 10-12. The G5-level storm, the most intense in the last two solar cycles, disrupted power grids and navigation systems around the world, but also provided observers with rare low-latitude views of brightly glowing auroras.
Also observing the storm that night, from its perch on a satellite in a geostationary orbit high above South America, was NASA’s Global-scale Observations of the Limb and Disk (GOLD) mission, which captured a never-before-seen phenomenon in the ionosphere—a narrow zone of charged particles in Earth’s atmosphere. During the storm, two parts of the ionosphere that are normally located at the equator and near the poles merged, causing the temporary disappearance of the mid-latitude ionosphere.
The observations were reported by researchers from the Laboratory for Atmospheric and Space Physics (LASP) and colleagues in an article, “GOLD Observations of the Merging of the Southern Crest of the Equatorial Ionization Anomaly and Aurora During the 10 and 11 May 2024 Mother’s Day Super Geomagnetic Storm,” published in the Aug. 9 issue of Geophysical Research Letters (GRL).
Unprecedented observations of the ionosphere
“This unprecedented event highlights the powerful impact that geomagnetic storms can have on Earth’s ionosphere, altering its structure and potentially affecting global communication and navigation systems,” said LASP researcher and lead author Deepak Karan. Other LASP co-authors included Richard Eastes and William McClintock.
The Earth’s ionosphere is typically divided into three regions: equatorial and low-latitude, mid-latitude, and high-latitude. Normally, the equatorial ionization anomaly (EIA) is a prominent feature in the equatorial and low-latitude ionosphere, characterized by two peaks, or areas of dense ionization, on either side of the magnetic equator.
However, during the recent geomagnetic storm, the EIA crests shifted dramatically poleward, moving to higher latitudes than ever previously recorded and at very high speeds. The southern EIA crest was clocked moving poleward at about 450 meters per second.
At the same time, the aurora, which usually hovers around 70 degrees latitude, expanded toward the equator, reaching latitudes as low as 40 to 50 degrees. The extreme nature of this storm caused the EIA crests and the aurora to merge, leading to the disappearance of the mid-latitude ionosphere—which has never been seen before, the authors reported.
“This is much different from anything that has been observed during five years of observations,” said LASP researcher Richard Eastes, principal investigator of the GOLD mission and co-author of the GRL paper.
The images above, from May 10 and 11, show the auroras (in red) and the equatorial crest (in blue green). The red areas are the northern and southern auroras.
“Seeing any aurora in the south, other than at the edge of the Earth, from GOLD’s location is unusual,” Eastes said. “The changes in the EIA are also unlike anything observed previously.”
As seen in the image, the V-shaped region in light blue green, which crosses South America then follows the South American coastline, is the southern crest of the EIA, which can be seen touching the southern aurora. “The 11 May images indicate that Earth’s magnetic high and low latitudes met during this storm,” Eastes said.
“These observations by GOLD provide us with a unique perspective on how the ionosphere reacts to severe geomagnetic disturbances,” said Karan. “They also demonstrate the complex relationship between solar activity and Earth’s upper atmosphere.”
Unprecedented observations of the thermosphere
The GOLD mission also observed extreme global changes—including higher temperatures, decreased ratios of oxygen to nitrogen, and high-altitude winds—in the thermosphere—a layer of the Earth’s atmosphere that extends from100 kilometers to ~1,000 kilometers altitude, exhibits high temperatures, and is influenced by solar ultraviolet radiation and geomagnetic activity.
The observations were reported by a team led by J. Scott Evans of Computational Physics, Inc., in the Aug. 16 issue of GRL. The paper, “GOLD Observations of the Thermospheric Response to the 10–12 May 2024 Gannon Superstorm,” was co-authored by several LASP researchers including Richard Eastes, Quan Gan, Fazlul Laskar, Saurav Aryal, Stéphane Béland, Xuguang Cai, Katelynn Greer, William McClintock, and Timothy Plummer.
Normally, during non-storm times, temperatures in the thermosphere peak at about 1,000 degrees Kelvin. Also, at that time of the year, there is normally a smooth gradient of the ratio of oxygen to nitrogen in the thermosphere—from a low in the northern hemisphere to a high in the southern hemisphere.
During the Gannon storm*, however, temperatures exceeded 1,250 degrees Kelvin at high latitudes where the team also observed a greater than 50 percent depletion in the ratio of oxygen to nitrogen. “When you have this kind of extreme heating, there is an expansion of the thermosphere and alterations of the winds globally,” said LASP researcher and co-author Katelynn Greer. The effects are an indication of the large amount of energy deposited into the thermosphere by the solar storm.
The GOLD observations revealed a never-before-seen structure in the chemical composition of the thermosphere. The image on the right shows the ratio of oxygen to nitrogen in the thermosphere globally during the May solar superstorm. Previously, researchers only had strips of measurements through these kinds of structures.”
“What is so special about this image is that it is a global snapshot of what is happening in the thermosphere,” Greer said. “All of these stunning images from GOLD show us that the thermosphere is a complex system that has entangled processes that change composition, temperature and winds, on a global scale.”
Further observations needed
To better understand this complex system, scientists need more data, including observations of the winds in the thermosphere, which future missions may soon be able to provide, Greer said, so that scientists may one day be able to forecast these effects and, ultimately, mitigate their impacts.
“The thermosphere is a critical component of our atmosphere that redistributes energy from storms in intriguing ways that we must do more to observe and understand—especially since these kinds of storms ultimately impact life, society, and economics on Earth,” Greer said.
The GOLD mission, for which LASP is the lead institution, launched on January 25, 2018, with a prime mission of two years. The spacecraft’s operation has been extended to continue providing data. GOLD fills a critical gap in our knowledge of Sun-Earth connections. It is examining the response of the upper atmosphere to forcing from the Sun, the magnetosphere, and the lower atmosphere. GOLD provides unprecedented imaging of Earth’s upper atmosphere to study the weather of the thermosphere-ionosphere. It has previously made breakthrough measurements of temperature and atmospheric composition that are important for predicting satellite drag as well as ionospheric disruptions of communications and navigation.
GOLD, which flies as a hosted payload on a commercial communications satellite provided by SES Space & Defense, was funded as a NASA Heliophysics Mission of Opportunity. Partner institutions on the mission include the University of Central Florida, National Center for Atmospheric Research, SES Space & Defense, National Oceanic and Atmospheric Administration, NASA’s Goddard Space Flight Center, University of California, Berkeley, Virginia Polytechnic Institute and State University, and Computational Physics, Inc.
*NOTE: Members of the space weather research community have proposed naming the May 10-12 event the Gannon Superstorm in honor of Jennifer Gannon, an early career space weather scientist who passed away suddenly on May 2, to honor her valuable contributions to the field of space weather.
—By Sara Pratt, LASP Sr. Communications Specialist
Founded a decade before NASA, the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder is on a mission to revolutionize human understanding of the cosmos by pioneering new technologies and approaches to space science. The institute is at the forefront of solar, planetary, and space physics research, climate and space-weather monitoring, and the search for evidence of habitable worlds. LASP is also deeply committed to inspiring and educating the next generation of space explorers. From the first exploratory rocket measurements of Earth’s upper atmosphere to trailblazing observations of every planet in the solar system, LASP continues to build on its remarkable history with a nearly $1 billion portfolio of new research and engineering programs, backed by superb data analysis, reliable mission operations, and skilled administrative support.
