On February 4, 2022, SpaceX launched 49 satellites as part of Elon Musk’s Starlink Internet project, most of which burned up in the atmosphere a few days later. The cause of the US$50 million-plus failure was a geomagnetic storm caused by the Sun.
Geomagnetic storms occur when space weather strikes and interacts with the Earth. Space weather is caused by fluctuations within the Sun that propel electrons, protons, and other particles into space.
I study the hazards that space weather poses to space assets and how scientists can improve space weather models and prediction to protect against these hazards.
When space weather reaches Earth, it triggers a lot of complicated processes that can cause a lot of problems for anything in orbit. And engineers like me are working to better understand these hazards and defend satellites against them.
What causes space weather?
The Sun always releases a constant amount of charged particles into space. This is called the solar wind. The solar wind also carries with it the solar magnetic field.
Sometimes localized fluctuations on the Sun will propel unusually strong particle bursts in a particular direction. If the Earth is in the path of the enhanced solar wind generated by one of these events and is affected, you get a geomagnetic storm.
The two most common causes of geomagnetic storms are coronal mass ejections — explosions of plasma from the Sun’s surface — and the solar wind escaping through coronal holes — low-density spots in the Sun’s outer atmosphere.
The speed at which the ejected plasma or solar wind arrives at Earth is an important factor — the faster the speed, the stronger the geomagnetic storm. Normally, the solar wind travels at about 900,000 mph (1.4 million km/h). But strong solar events can release winds up to five times faster.
The strongest geomagnetic storm ever recorded was caused by a coronal mass ejection in September 1859. When the mass of particles hit the Earth, they caused electrical surges in telegraph lines that shocked operators and, in some extreme cases, actually set fire to telegraph instruments.
Research suggests that if a geomagnetic storm of this magnitude hit Earth today, it would cause about $2 trillion in damage.
Emissions from the Sun, including the solar wind, would be incredibly dangerous to any life form unlucky enough to be directly exposed to them. Fortunately, the Earth’s magnetic field does much to protect humanity.
The first thing the solar wind hits as it approaches the Earth is the magnetosphere. This region surrounding the Earth’s atmosphere is filled with plasma composed of electrons and ions. It is dominated by the planet’s strong magnetic field. When the solar wind hits the magnetosphere, it transfers mass, energy and momentum into this layer.
The magnetosphere can absorb most of the energy from the daily level of the solar wind. But during strong storms, it can be overloaded and transfer excess energy to the upper layers of the Earth’s atmosphere near the poles. This redirection of energy to the poles causes fantastic aurora events, but it also causes changes in the upper atmosphere that can harm space assets.