On Tuesday, the sky will be alight. If you live in the northern hemisphere and the sky is clear, be sure to go outside and take a look around. NASA scientists and space weather stations are predicting widespread aurorae to be visible this evening, the result of a solar flare which erupted at 04:00 Coordinated Universal Time (UTC) on Monday morning. In some places, it's already happening.
The solar flare is impressive in its size, scope, and speed, but what's also impressive is the ability of modern science to directly observe the sun's activities. Sunspots are old, but our knowledge of them is still quite new.
Solar cycles responsible for sunspots, solar flares, and coronal mass ejections have likely been active for hundreds of millions of years, based on stratigraphic and tree ring (dendrochronologically dated radiocarbon) data analysis.
There are recorded observations of sunspots as far back as 364 BCE, but they remained a mystery until the early 17th century, when telescopes began to be employed and Renaissance astronomers looked through their new scientific instruments to view the sun. Galileo's Letters on Sunspots, published in 1613, was instrumental in demonstrating that the sun was a dynamic system — it changed over time — which of course contrasted with the ages-old conventional wisdom of Aristotle, who had maintained that all celestial bodies were perfect, static spheres incapable of change.
Flash forward 400 years to the present day, where we now have incredibly sophisticated telescopes capable of recording images of the dynamic nature of the sun, and we of course know that Galileo and his contemporaries pointed us in the right direction.
As Plait explains, we now know that "sunspots are regions where the magnetic field lines of the sun get tangled up" and when these lines are squeezed too tightly, the massive energy is released in a burst known as a solar flare. The particles blasted from this flare were travelling extremely quickly, covering the nearly 93 million-mile sun-Earth distance (which is known as an Astronomical Unit, or AU) in just a few hours.
The solar flare was followed by a less intense but larger phenomenon known as a coronal mass ejection, in which particles were once again launched into space, this time at much smaller speeds but aimed directly at the Earth. It is these slower particles, which first began to reach the Earth around 1400 UTC on Tuesday, which are responsible for the phenomenon known as an aurora, or the northern lights.
These particles interact with electrons high in the air, and when the electrons recombine, the atoms glow, lighting up the sky for our enjoyment.
The general consensus is that we have little to fear from this radiation, as the Earth's atmosphere protects us. Plait's tweet summarizes the lack of danger to Earth: "Our magnetosphere catches the solar particles & can funnel them into our atmosphere which stops them. No radiation gets through."
Even the astronauts aboard the International Space Station, far above the Earth's protective atmosphere, are not in any danger, and in fact, may be more protected from cosmic radiation during solar storms than they normally are, as solar particles tend to deflect cosmic rays away.
That's not to say that this type of solar activity is incapable of affecting us.
In 1989, power grids in Quebec, Canada, were affected by a solar storm as circuit breakers were tripped by variations in the Earth's magnetic field, leaving six million residents without power for more than nine hours. John Manuel of the Canadian Space Agency (CSA) also reports to CTV that in 1994, Canadian television signals were temporarily lost as a solar storm disrupted their signals.
So on this Tuesday evening, take a walk outside and hope for clear skies and colorful electron recombinations. Be comforted by the fact that Earth's atmosphere protects us, and reflect on how far we've come in the 400 years since Galileo first used his seventeenth century technology, when he pointed his telescope to the sun. In the 21st century, our technologies allow us to view the sun in a much more detailed manner, which aids in our understanding of the dynamics of the star and its relationship with the Earth. As you view the aurora tonight, consider how much of the universe's phenomena have been illuminated by modern science, whose wonders and accomplishments are many and always growing.
Photo Credit: NASA