Mild solar storms can cause more serious problems to GPS satellites than once-in-a-century events, a new study has found.
Storms that erupt from the sun create challenges for satellites in Earth's orbit. Scientists are trying to understand these events better to help operators protect their spacecraft. And sometimes, they find surprises.
A new study by researchers from the British Antarctic Survey (BAS) discovered that satellites in the Global Positioning System (GPS) orbit may suffer more from milder solar storms than from the frightening events that wreak havoc on power grids and telecommunication networks on Earth.
Nigel Meredith, a BAS space weather research scientist, and his colleagues analyzed 20 years worth of satellite data and found that the most challenging incident for U.S. GPS spacecraft — which provide critical services for many sectors, including all kinds of transportation, banking and oil drilling — came from a minor solar storm in 2010, during a sleepy part of the sun's 11-year cycle of activity. And the most significant space weather event in recent history, the 2003 Halloween storm, left the GPS satellites orbiting 12,550 miles (20,200 kilometers) above Earth mostly unscathed.
"Sometimes people think that when there's a superstorm, everything's going to happen at once. But from our study, it shows that that's not necessarily the case," Meredith told Space.com. "We saw the largest fluxes [of energetic particles from the sun] during what, many people might say, was a benign storm."
Solar storms are caused by interactions of the charged particles that make up solar wind with Earth's magnetic field and our planet's atmosphere. Solar wind is a stream of ionized gas that constantly trickles from the sun. During vast eruptions of solar material known as coronal mass ejections (CME), the sun hurls huge quantities of this solar wind into space at once.
Particles in the solar wind are magnetized, and when these huge plasma eruptions hit Earth's magnetic lines with the opposite magnetic pole, they temporarily disconnect the planet's protective magnetic shield and penetrate deep into the atmosphere. Reactions of the solar particles with atmospheric gases trigger colorful aurora displays but also induce electric currents that can, in the case of the most severe storms, knock out power grids and disrupt telecommunication networks.
There are several ways in which solar storms affect satellites. As solar wind particles mix with molecules of air, for example, the atmosphere warms up and swells, causing the density of the tenuous gases in the atmosphere's upper layers to increase. Spacecraft in low Earth orbit, including the International Space Station, suddenly experience more resistance and begin to lose altitude.