By Dr Tony Phillips, Spaceweather.com
A series of geomagnetic storms in 2023 has pumped terawatts of energy into Earth’s upper atmosphere, helping to push the temperature and height of Earth's upper atmosphere to a 20-year high. Air surrounding our planet is touching satellites in low Earth orbit and dragging them down.
"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."
Mlynczak has for 20 years been using the SABER instrument on NASA's TIMED satellite to monitor infrared emissions from "the thermosphere," the uppermost layer of the atmosphere. "Right now, we’re seeing some of the highest readings in the mission's over the 20 year history," he says.
"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 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.
"The two storms exceeding 1 TW are the seventh and eighth strongest storms observed by SABER over the past 21.5 years," he says. "It is interesting to note that each successive storm in 2023 is generally stronger than its predecessors."
It doesn't take a strong storm to cause problems. In Febuary 2022, a minor geomagnetic storm dumped enough heat into the thermosphere that 40 newly launched Starlink satellites fell out of the sky. SpaceX has since started launching their Starlinks to higher initial altitudes to avoid the growing aerodynamic drag.
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 tens of kilometres, increasing the risk of collisions and causing some of the lower ones to de-orbit.
