Getting Familiar with Space Weather: What Comes from the Sun?

Space Weather is something that has probably never crossed the minds of most people in the world. For the sliver of the population that has actually heard of it, space weather may still come across as a rather mysterious concept. And why shouldn’t it seem weird? Space weather encompasses a variety of thoroughly unfamiliar phenomena, and, unless you have had the fortune to observe the shimmering of the aurora in the night’s sky at the polar extremes of our planet, humans have no direct experience with the various happenings beyond the sky.

Of course, if you had been living your entire life in an enclosed room with neither windows, nor exits, nor the internet, stepping outside to find water falling on you from the sky would be awfully puzzling, too. The weather on Earth has many different manifestations—rain, hail, snow, thunder, lightning, tornados, hurricanes, floods, and so much more—and it would be very confusing to try to make sense of it all if we did not have a lifetime of experience to breed our familiarity with the weather. Of course, even with Earth’s weather, there are rare moments that can still surprise a forty-year old adult—like the first time I saw thundersnow on a chilly winter night in Iowa, or caught the sight of a desert rainstorm off in the distance where the raindrops evaporated before they hit the ground, a phenomenon known as virga. But the first time someone hears about all of the various aspects of space weather, it is all very new and sounds fantastic, and it may be difficult to make sense of it all.

Did You Say Ejection?

To make matters worse, space weather is often described in nearly indecipherable scientific jargon, making it hard for normal people to make heads or tails of what is being said (as opposed to scientists, who, it could be argued, are not exactly normal people.) For example, one of the most threatening occurrences in space weather is the coronal mass ejection, too often whittled down to just CME. This sounds like a serious medical condition, or perhaps an embarrassing night’s sleep for a teenage boy. It does not convey, to the common man or woman, a billion tons of electrified gas and magnetic fields hurtling towards the Earth at five million miles per hour. A much more evocative term, in my estimation, is a magnetic tsunami. My aim in Partly Cloudy with a Slight Chance of X-Rays: Space Weather Explained is to explain everything about space weather in terms that you can understand.

I am quite convinced that my having the audacity to introduce some new terms to describe the varied aspects of space weather will make many a professional space physicist cringe. But, to communicate scientific ideas to non-scientists using language that people can understand is important. Although technical terms convey a precise meaning to scientists, to regular people they often express much less. Scientists may protest loudly about my creating new terminology, but I will consciously sacrifice scientific precision to the evocative power of the English language, because this blog is not for scientists, but instead for everyone else. Below I will define these newly coined terms and explain my reasons for favoring them over the more technically precise standards. In addition, at the top of this blog, there is a glossary containing all of the terms (standard and new) that I have chosen to use, including their definitions and translations to more technically precise terms.

What Happens at the Sun Does Not Always Stay at the Sun

Everyone can appreciate the spectacular beauty of the aurora, but the aurora is really the final step in a long chain of events that starts at the sun. My goal is to convey the fascinating details of the entire process, so that everyone, not just scientists, can understand and appreciate, not only a dazzling auroral display, but all of the magnificent but invisible events leading up to it.

To put the menagerie of space weather effects into some semblance of order, it is helpful to make clear the separation between two concepts: first, the primary drivers of space weather that emerge from the sun; and, second, the impact that those drivers have on the Earth and its protective magnetic field. The sun directly controls space weather by launching mass and energy out into space towards the Earth. There are three distinct ways in which this occurs, corresponding to three of the key phenomena of space weather: solar flares, proton hailstorms, and magnetic tsunamis.

Solar flares blast the solar system with energy in the form of electromagnetic waves. Visible light is part of the spectrum of electromagnetic waves (corresponding to a wavelength of a few hundred nanometers)—a bright solar flare indeed sends out a flash of visible light. But the bulk of the energy in particularly strong solar flares emerges in the form of x-rays, electromagnetic waves of much shorter wavelength (less than ten nanometers) that carry a lot of energy.

Flare_AugX7

Solar Flare: An x-ray image of the sun, showing the intensely blinding x-rays from a class X7 solar flare. Credit: NASA.

Proton hailstorms occur when violent activity on the sun spews out very high energy particles (primarily protons, but also electrons and heavier elements, such helium, oxygen, and iron). The protons zip towards the Earth at about one third of the speed of light, or around 200 million miles per hour. It takes light about 8 minutes to travel from the sun to the Earth at light speed (670 million miles per hour), so a proton hailstorm reaches the Earth in about 30 minutes, with the storm lasting from hours to days. A solar energetic particle event is the technical term used by scientists to describe this type of space weather, and fast particles are commonly denoted with the abbreviation SEPs, a bland term that conveys little to the non-scientists.
The Space Weather Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) uses the slightly more descriptive term solar radiation storm, rating the severity of these storms on a scale from S1 to S5. But the rather vague term radiation is often highly misunderstood by the general population, typically evoking thoughts of the Cold War, or of a horribly painful death. As a technical term, radiation is so broadly defined that it can mean high-energy light waves called gamma rays (even shorter wavelength, and thus higher energy, than x-rays) or highly energetic particles, such as electrons or helium nuclei (also known as alpha particles). Most people don’t know that radiation is either some form of electromagnetic wave or a shower of fast particles. Both of these forms are microscopic and energetic, and can damage materials and living flesh (by damaging DNA and other biological components of your body at an atomic level). Because the cause of this harm is invisible, without scientific instruments it is not possible to determine whether waves or energetic particles are responsible, so the catch-all term radiation is used. I find that term radiation is not very telling about what is actually occurring, so I prefer the new term proton hailstorm, believing it to be far more illustrative than solar energetic particle event or solar radiation storm.

SpaceWeather_SEP_Satellite_ESA

Proton Hailstorm: A artist’s conception of a proton hailstorm inundating an Earth-orbiting satellite at five million miles per hour. Credit: European Space Agency (ESA).

The third type of space weather that can hurl both mass and energy toward the Earth is the magnetic tsunami. The sun is made up of gas, primarily hydrogen, with some helium and a very tiny amount of heavier elements such as carbon, nitrogen, and oxygen. This gas is so hot that it undergoes ionization, stripping electrons from the neutral atoms or molecules. The resulting morass of ions and electrons is known as a plasma, the fourth state of matter. Because plasmas are made up of charged particles, not only do they respond to the pressure forces that control the behavior of ordinary environments such as the air and water on Earth, but also they react to electric and magnetic fields. Particularly ferocious events on the surface of the sun can cause an explosion that hurls a massive cloud of magnetized plasma into space, leading to a magnetic tsunami plowing its way through the solar system at five million miles per hour. A severe magnetic tsunami may contain billions of tons of plasma with remnants of the sun’s magnetic field embedded inside. This event is much like a volcanic eruption on Earth that spews hot gas and dust into the air, but this eruption actually escapes the sun altogether, flying out into distant space. The scientific term for this occurrence is a coronal mass ejection, or CME, jargon that I find lacks any illustrative character.

CME_27Feb2000_SOHO

Magnetic Tsunami: Observations from NASA’s SOlar and Heliospheric Observatory (SOHO) showing a magnetic tsunami erupting from the sun on February 27, 2000. Credit: NASA.

What Happens Next?

When the sun throws a tantrum, it hurls light waves, particles, and magnetized plasma towards the Earth in the form of solar flares, proton hailstorms, and magnetic tsunamis. The situation becomes infinitely more complex when this barrage of mass and energy hits the Earth, impacting its protective magnetic field, and leading to an often confusing array of occurrences that comprises the rest of what we call space weather. Next time, we will place these effects on the Earth into the more familiar context of the weather that we experience on the Earth every day.

How’s the Weather Up There in Space?

Beware! Beware! A Big Solar Flare!

Every once in a while, you may see a story on the news about a massive solar flare, or some other potential catastrophe occurring out in space, that is said to have the potential to wreak havoc on life as we know it within the next 48 hours or so. But, a couple of days go by, your attention is drawn to other important matters, like a particularly bad morning commute, or that upcoming deadline for a project, and life goes on without the slightest hiccup from space. What is going on? Are the scientists just dead wrong, or simply exaggerating the potential hazards for some kind of gain—political, financial, or otherwise? And what in heavens do they mean by “space weather” anyway?

If you’ve ever had this experience, or if any of these questions have ever crossed your mind, then perhaps what follows will grab your interest, or even awaken a bit of fascination about what happens out there, above the sky.

The universe, and even our own solar system, can be a violent place. No, not the intentional kind of hateful violence perpetrated upon one woman or man by another, but the inevitable violence of a colossal earthquake that shatters homes and lives. Our weather on Earth is a natural phenomenon, familiar as the cold rain upon our skin, or the bright flash and trailing roar of a midnight thunderstorm. Beyond the atmosphere of the Earth, nature creates another kind of weather. Except for the dancing lights of the aurora at the northern and southern extremes of our planet, the weather in space is rarely experienced directly by humans, but instead must be measured by scientific instruments carried aloft on Atlas rockets. But although we cannot feel it, severe space weather does have the potential to impact significantly our daily lives, even though most of the population has little clue as to what space weather actually is.

Our Technology at Risk

How can an intense geomagnetic storm, for example, affect us? Curiously, harsh weather in space does not directly affect biological life—it cannot hurt us directly. The magnetic field of the Earth protects us from the brutal extremes of the space environment. But solar storms can excessively disrupt our lives by damaging or destroying the critical technology upon which our modern lifestyle depends—GPS navigation, radio communications, even the electrical power grid itself. Although it may sound like the plot of the next James Bond film, a major magnetic tsunami (or coronal mass ejection, as scientists call it) can drive a huge voltage spike in our power grid, burning out massive transformers that send to our homes the electricity that runs our computers, charges our cellphones, illuminates our TVs, and powers all of the other devices that pervade our daily lives. And recovery is not a matter of simply flipping a circuit breaker or replacing a burnt fuse. Replacing one ruined transformer is a major undertaking that could take weeks. Furthermore, for transformers of this size, few spares are held in reserve, so if enough of them are knocked out at once, it could take months to build the necessary replacements from scratch. How would your life change if you woke up one morning to discover the electrical power at your house would be out for the next three months?

But nothing of the sort has ever happened. Is such a doomsday scenario an extremely unlikely event, like the impact of a massive asteroid that killed off the dinosaurs 66 million years ago? The short answer is no. In fact, a sufficiently intense solar storm capable of causing this kind of havoc did happen in 1859, the infamous Carrington Event (named after the English amateur astronomer Richard Carrington who witnessed the massive solar flare that sparked the solar storm), just over 150 years ago. That no such extensive damage occurred is due simply to the fact that, in 1859, the surface of the Earth was not yet criss-crossed with the electrical wires of the modern power grid. The only wires covering sufficiently long distances to be affected were the sparsely distributed connections of the telegraph system, and deeply affected they were. The magnetic storm sparked fires at a few telegraph stations, gave some telegraph operators a potent electrical shock, and actually enabled messages to be sent with the system power switched off.

Predicting how often a major solar storm will occur is an imprecise business, like predicting the recurrence of other natural disasters, such as powerful earthquakes. One must rely on statistics derived from a very limited history of measurements, and we only learn how often an event is likely to occur based on that limited knowledge, not when one actually will occur. So when scientists caution that a magnetic tsunami headed in the general direction of the Earth may cause a damaging magnetic storm, their warning often highlights the worst case scenario. Catastrophe grabs headlines, so the media often cover the potential calamity but leave out the boring detail that there is only a 3% probability that the sky will actually fall. Nonetheless, our nation, along with the rest of the world, does need to prepare for what to do in the event of a potentially catastrophic solar storm. And, as a scientist, I take seriously the charge to educate the public about this invisible threat to our technological way of life.

What Exactly Is Space Weather?

OK, you have caught me, I am saving the best part for last. Just what is space weather?  Similar to the weather on Earth, there are many different manifestations of space weather, just like there are thunderstorms and floods and hurricanes. The sun is the ultimate energy source for all life on Earth, and it is also the origin of all space weather. Most of the time, conditions are calm. The sun bathes everything around it in the constant but mild glow of ultraviolet radiation and x-rays, and a steady solar wind blows through the solar system at a brisk million miles per hour.

But on rare occasions when the sun behaves badly, things get a lot more interesting. When the boiling surface of the sun forces a strong magnetic field pointing in one direction to crash into a powerful magnetic field pointing in another direction, the magnetic field lines can break and reconnect, snapping back like a broken rubber band and releasing a huge amount of energy in the process. That energy can generate a blinding solar flare, and in just eight minutes (the time it takes for light to reach us from the sun) the Earth’s atmosphere is bathed in an intense shower of x-rays. In addition to possibly damaging sensitive instruments on satellites, this flood of x-rays can lead to an ionization storm in the upper atmosphere that can disrupt radio communications with aircraft on polar flight paths between continents, temporarily cutting them off from the rest of the world.

The breaking of the magnetic field lines can also release billions of tons of plasma—the ionized gas of which the sun and its atmosphere are made—into interplanetary space, like a massive volcanic eruption escaping into space. This magnetic tsunami of hot plasma and its embedded magnetic field plows through the solar wind as it barrels like a runaway freight train out into the solar system at five million miles per hour. The impact of this behemoth on the steady solar wind flowing slowly before it can accelerate protons to nearly the speed of light, generating a proton hailstorm that showers whatever lies ahead. If the Earth is in the firing line, astronauts have ten minutes or less to seek shelter in a shielded compartment before being blasted by a deluge of high-energy protons that can pass right through their bodies, shredding their DNA on its way. Not only are human bodies at risk of catastrophic harm, but proton hail can also fry the electronics of communication and GPS navigation satellites, potentially taking out vital pieces of our technological infrastructure worth hundreds of millions of dollars.

But the greatest impact of severe space weather on our technology, and thus our lives, can occur if the magnetic tsunami itself is headed directly toward the Earth. As the magnetic tsunami collides with and compresses the Earth’s protective magnetic field, it can trigger an intense magnetic storm, causing a small but sudden change in the magnetic field at the Earth’s surface that can have dire consequences. The fundamental laws of physics tell us that a changing magnetic field induces an electric voltage. In the case of a powerful magnetic storm, that sudden spike of thousands of volts can short circuit and burn out the mammoth power transformers that enable electricity to be sent efficiently over long distances, potentially crippling our power grid, immersing us in inevitably dark nights for a period that could last from weeks to months, depending on the severity of the storm.

But beyond these warnings of potential doom and gloom, severe space weather has an enchanting upside, too. When a magnetic tsunami collides with the Earth’s magnetic field, the magnetic field lines can break and reconnect there as well. This shifting of the magnetic fields, forty thousand miles above the Earth’s surface, generates waves that travel downward along the magnetic field lines toward the northern and southern poles. At an altitude of about five or six thousand miles, the waves speeding ever more rapidly toward the surface bounce electrons out in front of them, toward the upper atmosphere below. A hundred miles above the ground, the electrons collide with the thin air in the upper atmosphere, exciting the molecules and inducing them to radiate their excited energy away as the colorful, dancing lights of the aurora.

Follow Along to Learn More about Space Weather

In the coming weeks and months, come back to Partly Cloudy with a Slight Chance of X-rays: Space Weather Explained to learn more about severe space weather, about the efforts of scientists to study space weather and their program to develop the capability to predict the weather in space, and about government efforts to prepare our nation to protect our technological infrastructure from damage and to recover rapidly from future space weather catastrophes. Subscribe to this blog, or follow me on Twitter (@profgxray) to be informed each time a new chapter appears!