Scientists at MIT’s Haystack Observatory and the University of Colorado have observed the sudden and dramatic effect of a solar shockwave as it hit Earth’s radiation belts.
In October 2013, a massive explosion on the sun’s surface sent a blast of solar wind out into space. This shockwave slammed into the Earth’s magnetic field, setting off a magnetized sound pulse around our entire planet. This pulse accelerated certain lightweight particles throughout Earth’s radiation belts.
“These are very lightweight particles, but they are ultrarelativistic, killer electrons — electrons that can go right through a satellite,” says John Foster, associate director of MIT’s Haystack Observatory. “These particles are accelerated, and their number goes up by a factor of 10, in just one minute. We were able to see this entire process taking place, and it’s exciting: We see something that, in terms of the radiation belt, is really quick.”
NASA’s Van Allen probes captured effects of the shock wave as it hit Earth’s radiation belts and immediately after. For the first time ever, scientists were able to use the data from the Van Allen probes to document the effects of a solar shockwave on Earth’s radiation belts from beginning to end.
The Van Allen probes have been orbiting within in the Van Allen radiation belts since August 2012. There’s two probes in total, with one following the exact same orbit as the other – but an hour behind it. In October 2013, the lead Van Allen probe just happened to be at the right spot to watch the shockwave hit the radiation belts. The second probe documented the aftermath.
Why are scientists so interested in the shockwave’s effects on our radiation belt? Remember those particles that get accelerated? They accelerate to a blistering 1,000 kilometers per second and can pass right through satellites and damage their electronic systems.
As the solar shockwave made impact, according to Foster, it struck “a sledgehammer blow” to the protective barrier of the Earth’s magnetic field. But instead of breaking through this barrier, the shockwave effectively bounced away, generating a wave in the opposite direction, in the form of a magnetosonic pulse — a powerful, magnetized sound wave that propagated to the far side of the Earth within a matter of minutes.
This shockwave is a small one according to Foster. “We know they can be much, much bigger,” says Foster.
Foster adds, “Interactions between solar activity and Earth’s magnetosphere can create the radiation belt in a number of ways, some of which can take months, others days. The shock process takes seconds to minutes. This could be the tip of the iceberg in how we understand radiation-belt physics.”