"Blame the sun," says Martin Mlynczak of NASA Langley. "Increasing solar activity is heating the top of the atmosphere. The extra heat has no effect on weather or climate at Earth's surface, but it's a big deal for satellites in low Earth orbit."
photographed by Michael Underwood from Yellowstone National Park
The thermosphere is exquisitely sensitive to solar activity, readily absorbing energy from solar flares and geomagnetic storms. These storms have been coming hard and fast with the recent rise of Solar Cycle 25.
"There have been five significant geomagnetic storms in calendar year 2023 that resulted in marked increases in the amount of infrared radiation (heat) in Earth's thermosphere," says Mlynczak. "They peaked on Jan. 15th (0.59 TW), Feb. 16th (0.62 TW), Feb. 27th (0.78 TW), Mar. 24th (1.04 TW), and April 24th (1.02 TW)."
The parenthetical values are TeraWatts (1,000,000,000,000 Watts) of infrared power observed by SABER during each storm. The sensor obtains these numbers by measuring infrared radiation emitted from nitric oxide and carbon dioxide molecules in the thermosphere.
So far, Solar Cycle 25 is far ahead of Solar Cycle 24. Credit: Linda Hunt
If current trends continue, the thermosphere will warm even more in 2023 and 2024. This is a matter of concern because Earth's population of active satellites has tripled since SpaceX started launching Starlinks in 2019. The growing constellation of 4100 Starlinks now provides internet service to more than a million customers. An extreme geomagnetic storm like the Halloween Storms of 2003 could shift the positions of these satellites by many 10s of kilometers, increasing the risk of collisions and causing some of the lowest ones to de-orbit.
Stay tuned as the warming continues.