On May twenty-third, nineteen sixty-seven, the US Air Force nearly started a war. It was during the most intense phase of the Cold War. On that day, the American missile warning system, which was supposed to detect threats from the Soviet Union, suddenly stopped working. Radar stations at all locations in the northern hemisphere appeared to be blocked. U.S. Air Force officials thought the Soviet Union had attacked their radar and started preparing for war. Then they realized it wasn’t the Soviets. It was a solar storm.
What are solar storms, how dangerous are they and what can we do about them? That’s what we’ll talk about today.
First things first, what is a solar storm? The sun is so hot that electrons in it are not bound to atomic nuclei, but can move freely. Physicists call this state a “plasma”. When electrical charges move in the plasma, it builds up magnetic fields. And the magnetic fields move more electrical charges, which increases the magnetic fields and so on. In this way, the sun can build up enormous magnetic fields that are powered by nuclear fusion.
Sometimes these magnetic fields form arcs over the sun’s surface, often in an area with sunspots. These arcs can tear off and tear off and then two things can happen: Firstly, a lot of radiation is suddenly released, that is visible light, but also ultraviolet light and up to the X-ray range. This is known as a solar flare. The radiation is usually accompanied by some fast moving particles called solar particles. Second, in some cases, the torch comes with a shock wave that hurls some of the plasma into space. This is known as “coronal mass ejection” and can be billions of tons of hot plasma. The solar flare together with the coronal mass ejection is called a “solar storm”.
A solar storm can last minutes to hours and can release more energy than all of the energy we have expended in human history. The sun’s activity has an 11-year cycle, and the worst solar storms often occur in the years after the solar maximum. We are just beginning a new cycle and the next solar activity peak will be around 25. Then come the statistically most dangerous years of the solar cycle.
Well actually. The solar cycle actually lasts 22 years, because after 11 years the magnetic field reverses and the cycle is only completed when it returns. Only 11 years are the relevant cycle for solar activity.
How do these solar storms affect us? Space is big and most of these solar storms are not going in our direction. When it does, the solar flare is moving at the speed of light and takes about eight minutes to reach us. The associated radiation exposure poses a health risk for astronauts and pilots and can affect satellites in orbit. For example, during a solar storm in 2003, the Japanese weather satellite Madori 2 was permanently damaged and many other satellites shut down automatically because their navigation systems were not working. This solar storm became known as the 2003 Halloween Storm because it occurred in October.
Down here on earth we are mostly shielded from the torch. Not so with coronal mass ejection. It comes after the flare with a delay of twelve hours to three days, depending on the initial speed, and carries its own magnetic field. When it reaches the earth, this magnetic field combines with that of the earth. One effect of this is that the aurora becomes stronger, can be seen closer to the equator and can even turn its color into red. During the Halloween storm he could be seen as far as the Mediterranean Sea and also in Texas and Florida.
The aurora is pretty and mostly harmless, but the magnetic field causes a big problem. Because it changes so quickly, it induces electrical currents. The earth’s crust is not very conductive, but our power grids are very conductive due to their construction. This means that the solar storm’s magnetic field moves a lot of currents in the power grid, which can damage power plants and transformers and cause power outages.
How big can solar storms get? The strength of solar storms is measured by the energy output of the solar flare. The smallest are called A grade and are near the background level, followed by B, C, M, and X grades. This is a logarithmic scale so each letter represents a 10x increase in energy output. There are no more letters after X, instead numbers are added after X, for example X10 is another 10-fold increase after X.
What is the biggest solar storm of all time? It could have been September 2, 1859. The solar flare that day was accidentally observed by the English astronomer Richard Carrington, which is why it is now known as the “Carrington Event”.
The coronal mass ejection after the flare migrated directly towards Earth. Back then there weren’t many power grids that could have been damaged because electric light wouldn’t become common in cities for about two decades. But they had a telegraph system.
A Philadelphia telegraph operator was severely electrocuted while testing his equipment and most of the equipment stopped working because it couldn’t handle the current. But some telegraphers found that they could keep using their device if they unplugged it, just with the current induced by the solar storm. The following exchange took place during the Carrington event between Portland and Boston:
“Please disconnect your battery completely from the line for fifteen minutes.”
“Will do it. It’s separate now.”
“Mine is not connected and we work with the aurora borealis.
“Better than with our batteries. – Electricity comes and goes little by little.”
“My current is sometimes very strong and we can do better without batteries as the Aurora seems to take turns neutralizing and amplifying our batteries, sometimes making the current too strong for our relay magnets. Suppose we work without batteries while we are affected “by this trouble.”
How strong was the Carrington event? We don’t really know. At that time, two measuring stations in England tracked the magnetic field on earth. But these devices worked by sliding an ink stick around on the paper, and during the height of the storm that pen just ran off the page. It was estimated by Karen Harvey to have a total energy of up to 10³² ergs, which puts it roughly in the X45 category. You can read more about the Carrington event in Stuart Clark’s book “The Sun Kings”.
At twenty-three, Lloyd’s insurance market estimated that a solar storm similar to Carrington’s today would cause damage to the power grid between zero point six and two point six trillion US dollars – for the United States alone. That’s about twenty times the damage caused by Hurricane Katrina. Power outages could last anywhere from a few weeks to two years because so many transformers would need to be replaced.
The strongest torch measured with modern methods was the Halloween Storm 2003. Again it was so strong that it overloaded the detectors. The sensors switched off at X 17. It was later estimated to be X 35 +/- 5, slightly below the Carrington event.
How bad can solar storms get? The magnetic field of our planet shields us from particles that constantly come from the sun, the so-called solar wind. It also prevents these solar particles from tearing the atmosphere off our planet. Mars, for example, once had an atmosphere, but because Mars has a weak magnetic field, its atmosphere was wiped away by the solar wind. A solar storm that overstrains the protection we have from our magnetic field could expose us to the raining plasma and, in the worst case, tear our atmosphere completely or partially apart. Can such strong solar storms happen?
Well I hope you are seated because from all I can say the answer is not an obvious “no”. The more energy a solar storm has, the less likely it is. But on occasion, astrophysicists observe stars very similar to our Sun that have a solar flare so large that they could endanger life in the habitable zone. You currently do not know whether such an event is possible for our sun or how likely it is.
I didn’t know that when I started working on this video. Sorry for the bad news.
What can we do against it? Satellites in orbit can be shielded to a certain extent. Aircraft can be diverted to lower latitudes or altitudes to limit the exposure of pilots and passengers to radiation. We can cut part of the power grid to prevent currents from moving too easily. But other than that, the best we can do to prepare for what’s to come, maybe stock up on toilet paper. How well these preparations work depends crucially on how far we know that a solar storm is coming. That is why scientists are currently working on solar weather forecasts that may warn us of the flare.
And about these mega-storms. We don’t currently have the technology to do anything about it. I think the best we can do is invest in scientific research and development so that one day we can protect ourselves.
Thanks for watching, don’t forget to subscribe, see you next week.