A solar shockwave surrounding Earth has been witnessed for the first time, by the Van Allen probes, operated by NASA.
On October 8, 2013, a wave of solar wind erupted at supersonic speeds from the Sun, and headed toward our home planet. Then the blast of charged particles arrived at Earth, they struck our planet's magnetic field, generating a magnetized pulse that raced around the globe.
Data of this event, recorded by the Van Allen, was carefully analyzed by astronomers. They found that a magnetosonic pulse, lasting 60 seconds, engulfed the planet. This event provided some particles with vast amounts of energy, accelerating them to tremendous velocities.
The Van Allen probes have been orbiting within Earth's Van Allen radiation belts since August 2012. The purpose of the mission is to explore conditions within the belts, in order to assist researchers in designing satellites and other spacecraft that can withstand the harsh environment.
Some particles, driven by the solar shockwave, can travel at ultrarelativistic velocities, racing around the planet in just five minutes.
When the blast of solar wind hit the Earth on October 8, 2013, one of the pair of satellites recorded conditions in the radiation belts just before the blow, while the other was able to measure the after effects of the event.
The magnetosonic pulse, a magnetized sound wave, was generated by a rebounding effect from charged particles in the solar wind striking the powerful radiation belts. When this event occurred, a racing electric field generated 10 times the normal number of ultrarelativistic electrons. When these particles travel at velocities matching that of the magnetosonic pulse, they are more likely to gain energy, and speed along at tremendous speeds.
Similar events happen about twice a month, according to researchers. The 2013 occurrence was relatively minor, compared to some other shockwaves.
"This was a relatively small shock. We know they can be much, much bigger. 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," John Foster of Haystack Observatory said.
These events could produce some of the most dangerous radiation that could damage human space travelers, or delicate electronics aboard spacecraft. Researchers hope their investigations of interactions between the Van Allen Belts and solar wind could provide data needed to properly protect these spacecraft.
Analysis of the strike of solar wind was published in the Journal of Geophysical Research.
