I want to thank Ian Sales twice. First, for accepting A Ray of Sunshine for his critically acclaimed anthology Rocket Science. Secondly, for extending an invitation for a guest blog post in Rocket Science News. I appreciate this, for A Ray of Sunshine dealt with radiation in space. But that ray of sunshine occasionally hits home, and it can be disastrous.
Let’s back up a bit. The Sun is a gigantic unshielded fusion reactor. All kinds of fusion debris comes blasting out of the Sun. Visible light, of course, and radiation throughout the spectrum. Atomic debris of all kinds, from iron ions down to electrons, makes up the solar wind that fills our solar system out to the heliopause, nearly 100 AU from the Sun. The Earth’s atmosphere is pretty good at stopping the debris from reaching the surface. It also filters out the ionizing radiation from the X-ray and gamma bands. But there’s some energy that gets straight through to us on the surface.
Hans Christian Ørsted demonstrated that electrical flow generates a magnetic field. On the Sun, titanic flows of charged plasma flow throughout the convective layer. Those flows generate magnetic fields. Because the Sun rotates faster at the equator than at its poles, the fields will get tangled up with each other. Energy compresses these tangles closer together, along with the trapped plasma. Then, ignition. A solar flare is born.
With the force of petatons of TNT, the magnetic lines of force realign and smooth out. A bubble of magnetic energy is pinched off and hurled off the Sun, never to return. Ionized matter is dragged along with the magnetic field, like leaves behind a car. This is the Coronal Mass Ejection, or CME, that so worries space weather experts.
Earth, fortunately, has a magnetic field of its own. It extends out into space like an enormous teardrop, with the tail pointing away from the Sun. It acts as a buffer to most of the solar wind, guiding ionized particles away from the surface. On Earth, we measure a constant magnetic field, pointed roughly towards true north.
When a CME sweeps by Earth, many different effects occur. The blast of charged particles affect satellites, sleet through astronauts, and drill down around the poles, sparking aurorae. The Van Allen belts get pumped full of ions, and the upper atmosphere changes under the onslaught, ruining radio communications.
Then there’s the flare’s magnetic energy. It is much stronger than the magnetic field of Earth, and penetrates all the way to the surface. We humans don’t perceive anything, but if you’re an electrical conductor, the story is far different.
A truly amazing amount of infrastructure has been built in the developed countries. Water mains, electrical generation and distributions systems, oil and natural gas lines, railroads–all of these are very long stretches of metal. When the flare’s magnetic bubble sweeps by, it induces an electrical current in those long stretches of conductor. Even though most flares generate at most a hundred nanoTesla of magnetic energy on Earth, over the course of hundreds of kilometers, some truly impressive voltages can be induced. If utility operators are not prepared for these spurious currents, they risk destruction of parts of their infrastructure.
On September 1st 1859, English astronomer Richard C. Carrington witnessed a solar flare in broad daylight. This event has been ranked as one of the most powerful solar flare witnessed in the modern era. Telegraph operators were either shocked unconscious, others were able to run their equipment solely on these geomagnetic induced currents. The magnetometers of the time measured the magnetic deviation on the order of 1500 nanoTesla.
On March 13th, 1989, the province of Quebec was plunged into darkness for nearly twelve hours when geomagnetic induced currents damaged transformers and line conditioners in several areas. Photos of the damage show the cores of transformers with the laminations bent away from each other by the force of geomagnetic induced eddy currents. In New Jersey, the Salem nuclear power plant’s power conditioning equipment suffered damage when DC currents of thousands of volts and hundreds of amperes entered the system from both the transmission lines as well as the grounding piles.
The 1989 event was the result of an X15 solar flare. And that’s not even the strongest one recorded. On November 4th 2003, an X28 flare occurred, but luckily it erupted when it was on the western limb of the Sun, and the CME missed Earth.
Today’s world is more complex and interconnected than the world of 1859 or even 1989. Not only are we ever more dependent on computers with their finicky power requirements, but we are invisibly, and often unknowingly, bound to satellite services that can be disrupted by powerful solar flares. Would you want to be on an unpiloted plane that just lost its GPS signal?
The current Solar Cycle 24 peaks in 2013. We have been fortunate so far in that this cycle appears to be less stormy than Cycle 23 or 22. It only takes one large flare, pointed at Earth, to push a bubble of plasma and magnetic energy our way. When that happens, a Ray of Sunshine will hit home. The main question is, will we be ready?
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