Thursday, June 23, 2022

Wild solar weather is causing satellites to plummet from orbit.

 In late 2021, operators of the European Space Agency's (ESA) Swarm constellation noticed something worrying: The satellites, which measure the magnetic field around Earth, started sinking toward the atmosphere at an unusually fast rate — up to 10 times faster than before. The change coincided with the onset of the new solar cycle, and experts think it might be the beginning of some difficult years for spacecraft orbiting our planet. 

"In the last five, six years, the satellites were sinking about two and a half kilometers [1.5 miles] a year," Anja Stromme, ESA's Swarm mission manager, told "But since December last year, they have been virtually diving. The sink rate between December and April has been 20 kilometers [12 miles] per year."

Satellites orbiting close to Earth always face the drag of the residual atmosphere, which gradually slows the spacecraft and eventually makes them fall back to the planet. (They usually don't survive this so-called re-entry and burn up in the atmosphere.) This atmospheric drag forces the International Space Station's controllers to perform regular "reboost" maneuvers to maintain the station's orbit of 250 miles (400 km) above Earth. 

Scientists know that the intensity of this drag depends on solar activity — the amount of solar wind spewed by the sun, which varies depending on the 11-year solar cycle. The last cycle, which officially ended in December 2019, was rather sleepy, with a below-average number of monthly sunspots and a prolonged minimum of barely any activity. But since last fall, the star has been waking up, spewing more and more solar wind and generating sunspots, solar flares and coronal mass ejections at a growing rate. And the Earth's upper atmosphere has felt the effects.

"There is a lot of complex physics that we still don't fully understand going on in the upper layers of the atmosphere where it interacts with the solar wind," Stromme said. "We know that this interaction causes an upwelling of the atmosphere. That means that the denser air shifts upwards to higher altitudes."

Denser air means higher drag for the satellites. Even though this density is still incredibly low 250 miles above Earth, the increase caused by the upwelling atmosphere is enough to virtually send some of the low-orbiting satellites plummeting. 

In February, SpaceX lost 40 brand-new Starlink satellites that were hit by a solar storm just after launch.

By coincidence (or beginner's luck), the onset of the new space revolution came during that sleepy solar cycle. These new operators are now facing their first solar maximum. But not only that. The sun's activity in the past year turned out to be much more intense than solar weather forecasters predicted, with more sunspots, more coronal mass ejections and more solar wind hitting our planet.

"The solar activity is a lot higher than the official forecast suggested," Hugh Lewis, a professor of engineering and physical sciences at the University of Southampton in the U.K. who studies the behavior of satellites in low Earth orbit, told "In fact, the current activity is already quite close to the peak level that was forecasted for this solar cycle, and we are still two to three years away from the solar maximum."


  1. Hams keep a close watch on the sun for propagation

  2. The Brits are watching the sun very closely. The Royal Astronomical Society issued this report in 2015 that Earth is heading for a mini ice age in the 2030's the likes of which haven't been experienced since 1645. These 11 year heartbeats are becoming irregular and Greta might have to leave Sweden and move to the Congo.

  3. If you look at the progression of the current cycle, 25, yes it is a bit higher than predicted, but it's still only a little stronger than 24 was at this point in the cycle. Cycle 24 was the weakest in over a hundred years, so it's a little stronger than that, but still much weaker than the next weakest cycles in the last 50 years.

    Graph here:
    referenced here at the bottom of the page:

  4. Ooops. Hit the button I didn't mean to.

    It might be worthwhile to consider the explanation might be that the Earth's magnetic field is weakening at the fastest rate ever seen. The magnetic field protects against solar wind or coronal mass ejections, so maybe it's not so much the cycle's strength as the weakening shield letting more in.

  5. And just think, fossil fuel is causing this as well and all we need do is destroy our economy.

  6. Another Carrington Event and the electrical grid could go down for years. Think how dependent the modern world is on electricity.

  7. I have a prediction: Shit happens.