The term “space weather” will be new to some, but it’s becoming more and more important to be aware of. Space weather refers to the effect of solar emissions on our satellites and astronauts in space, as well as our electronics and electrical systems on Earth. By solar emissions we mean the solar wind, solar flares, and bigger events, called coronal mass ejections (CMEs).
Huge solar flares send charged particles toward Earth. Our magnetic field (the purple areas) and out atmosphere help protect us. Credit: NASA
If Earth is in the line of fire during a solar flare or CME, we are fairly well protected with our magnetic field and our atmosphere. But often the charged particles in the solar wind and emissions get through and we get auroras, or northern lights, for example. If the solar outbursts, or geomagnetic storms, are really large, then more charged particles get through, and they interfere with our electronics and electrical systems on Earth. One extreme example is the Carrington Event.
On September 2, 1859, a British astronomer named Richard Carrington was observing sunspots when he happened to observe a white solar flare on the Sun, which produced a huge CME. At the time, the science of space weather did not exist. Within hours, amazingly bright auroras appeared as far south as the tropics, which is not normal. In one report, the aurora was so bright that it woke up gold miners in the Rocky Mountains at 1:00 a.m.! They thought it was morning!
The geomagnetic storm was so strong that it caused electrical fires and knocked out several telegraph systems that took weeks to fix. Imagine what such a storm would do to our electronics and electrical systems today, being so much more extensive than in 1859. Although the electronics in satellites are made to withstand solar radiation, a major event could wipe out communications, Internet, and GPS services—a real disaster!
This graphic by the European Space Agency shows how excessive solar emissions can harm our astronauts, satellites, and electrical systems. Credit: ESA/Science Office, CC BY-SA 3.0 IGO
In a more recent example, on February 3, 2022, SpaceX launched 49 Starlink satellites. These satellites start off in a low-Earth orbit, about 200 kilometres above Earth’s surface. Eventually, they reach their operating altitude of about 550 kilometres. (Other satellites are in higher orbits: the International Space Station is around 400 kilometres above Earth’s surface, and our GPS satellites are around 20,000 kilometres above Earth’s surface.)
The next day, on February 4, there was a geomagnetic storm. Another effect of geomagnetic storms is that they warm up the atmosphere. When the atmosphere warms up, the density increases. When the density increases, atmospheric drag increases; in other words, more drag means that anything in the atmosphere starts to slow down faster than normal. While the atmosphere is pretty thin at 200 kilometres above Earth’s surface, it’s thick enough to affect the Starlink satellites. And it did. The drag proved to be too much. Most of the satellites couldn’t recover from the difference in drag, and maybe 40 of them will re-enter the atmosphere (if they haven’t already) and burn up. But at least that means there won’t be any space debris or danger to lives on Earth of falling satellite parts.
Space weather can also hurt any astronauts in space. During the Apollo Moon missions from 1969 to 1972, Canadian astronomers at the Algonquin Radio Observatory in Algonquin Park monitored the Sun, looking for any storms that could harm the astronauts. Had there been any, the astronauts could have been seriously harmed by the radiation, since the Moon has no atmosphere to protect them, and Earth’s magnetic field won’t help because the Moon is not within it. If needed, the Apollo astronauts would have left the lunar surface and sought protection in the Command Module in lunar orbit, which had thick walls to provide some protection from the radiation.