Earth’s thermosphere recently hit a near 20-year temperature peak after absorbing energy from geomagnetic storms that bashed Earth this yr. The temperature within the second-highest layer of the atmosphere will likely proceed to climb over the following few years because the sun’s activity ramps up, which could impact Earth-orbiting satellites, experts warn.
The thermosphere extends from the highest of the mesosphere, at around 53 miles (85 kilometers) above ground, to the underside of the exosphere, which begins at around 372 miles (600 km) above the bottom, in accordance with NASA. Beyond the exosphere is outer space.
For greater than 21 years, NASA has measured the thermosphere temperature via infrared radiation emitted by carbon dioxide and nitric oxide molecules. Scientists convert data collected by NASA’s Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite, into the Thermosphere Climate Index (TCI), which is measured in terawatts, or TW. (1 TW is the same as 1 trillion watts.)
The TCI value, which spiked on March 10, peaked at 0.24 TW, Martin Mlynczak, a number one researcher on the TIMED mission at NASA’s Langley Research Center in Virginia and creator of the TCI, told Live Science. The last time the TCI was this high was Dec. 28, 2003. (The temperature spike data has been submitted to a journal but has not yet been peer-reviewed.)
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The temperature spike was brought on by three geomagnetic storms in January and February — major disturbances to Earth’s magnetic field which might be triggered by chunks of fast-moving magnetized plasma, often called coronal mass ejections (CMEs), and fewer often by streams of highly charged particles, often called solar wind, that are each spat out by the sun.
“These ‘storms’ deposit their energy within the thermosphere and cause it to heat up,” Mlynczak said. “The increased heating leads to increased levels of infrared emission from nitric oxide and carbon dioxide within the thermosphere.” Normally, infrared emissions after a storm cool the thermosphere, he added, but when the storms come back to back the temperature stays high.
Because the spike, a minimum of two more geomagnetic storms have hit our planet — one on March 24, which was the strongest solar storm to hit Earth for greater than six years, and one other equally powerful storm on April 24. The TCI values following these storms have remained high but haven’t yet passed the March peak, Mlynczak said.
Geomagnetic storms develop into more frequent and intense during solar maximum, a component of the roughly 11-year solar cycle by which the sun is most energetic and covered in dark sunspots and plasma loops that spit out CMEs and solar wind.
Consequently, Earth’s thermosphere also follows a roughly 11-year cycle, Mlynczak said. Government scientists from NASA and NOAA predicted the following solar maximum will arrive in 2025, which suggests the warming trend will likely proceed over the following few years.
Changes to the thermosphere can pose challenges for satellites in low-Earth orbit which might be positioned across the thermosphere’s upper boundary, Mlynczak said.
“The thermosphere expands because it warms,” Mlynczak said, leading to “increased aerodynamic drag on all satellites and on space debris.” This increased drag can pull satellites closer to Earth, he said, which could cause satellites to crash into each other or completely fall out of orbit, as SpaceX Starlink satellites did in February 2022 after a surprise geomagnetic storm.
Satellite operators can avoid these issues by positioning their spacecraft in the next orbit when needed, however the unpredictability of space weather makes it hard to know when these maneuvers are required until it is commonly too late.
Solar maximum could also arrive prior to predicted. A recent study published Jan. 30 within the journal Frontiers in Astronomy and Space Sciences suggests that the solar activity peak could arrive as early as late 2023 and be more powerful than initially predicted. If this scenario plays out, then the chance of a satellite disaster further increases.
Nonetheless, over longer timescales, temperatures within the thermosphere are declining, because excess CO2 within the thermosphere resulting from climate change increases infrared emissions into space, a May 8 study within the journal Earth Atmospheric and Planetary Sciences found.