Helio-meteorology is the study of the Sun’s weather and how it affects weather here on Earth. It is such a new term that currently my spell-check doesn’t consider it a word yet. Despite visually seeing phenomena such as sunspots and recording them as early as 324 BC in China, they were thought to be other planets moving in front of the sun until 1612, when Galileo was able to demonstrate that these “dark spots” were on the sun itself. It wasn’t until the proliferation of the space-age and the development of multiple NASA projects nearly 400 years later, that humans started to learn enough about our Sun to begin to understand how it works. Surprisingly enough, the more we are learning about the Sun, the more we’re starting to realize that our lives are more closely intertwined with the Sun than we have assumed for thousands of years.
The Sun is essentially an enormous ball of super-heated gas. If you ignore the extreme heat and pressure, and you’re essentially left with just a giant ball of gas. We know from our own atmosphere and simply seeing a cloudy day that in a gaseous environment, not all parts of the atmosphere are exactly the same at any given moment. Some areas are rainy, others are sunny, and it’s always changing. Scientists have known about large windy storms on Jupiter and other planets in our solar system for decades now. With what we understand about how atmospheres exist on planets, we have enough evidence to at least deduce that there must also likely be weather-like effects within the surface of the Sun…or at least we did 20 years ago.
Nowadays, we know for a fact that there are weather patterns on the surface of the Sun. NASA has an entire web-page devoted to monitoring the Sun’s solar activity 24/7 and is set up to issue world-wide alerts in the event they need to. In fact, I’m still surprised that solar weather conditions aren’t posted on television, such as on the Weather Channel, as scientists have been aware for years that solar activity affects the Earth’s average temperature as much or more than greenhouse gas emissions. In fact, here are all of the causes in order of most to least influence of the temperature of a planet, as listed by Wikipedia:
1. Incident radiation from the Sun
2. Emitted infrared radiation from the planet’s surface
3. The Albedo Effect, or the amount of light reflected by the planet’s surface
4. The Greenhouse Effect, or the amount of light absorbed by a planet’s atmosphere
5. Internal energy, such as tidal heating, radioactive decay, gravitational pressure, etc.
Notice anything about that list? Perhaps that the Sun is the first and by far the most influential source of the temperature for our planet, and the Greenhouse Effect is fourth? Whittled to the most basic of terms, the Albedo Effect focuses on the amount of light reflected by, and thus, the color of our planet. This literally means that the fact that our planet is dark blue instead of bright white (like the moon) causes more of an effect on climate change than greenhouse gas emissions alone. Sounds like hogwash? Here’s a practical, everyday example that you can try for yourself:
Go outside to the closest place where your sidewalk touches your street. Make sure it’s a bight sunny day and it’s about mid-afternoon for the best effect. Place one hand on the asphalt and one hand on the sidewalk, and wait. If you’re hands are able to sense heat at all, you’ll immediately notice that the hand touching the asphalt street is much hotter than the hand touching the concrete sidewalk. This temperature difference is literally because of the color difference between concrete and asphalt (as it certainly isn’t because the greenhouse gasses near your left hand are different than those to your right). It is a known scientific fact that darker colors absorb more light than lighter colors; it is the very concept with which humans see and process color.
So now that we have established that the sun does indeed have weather patterns and its output does in fact affect the overall temperature and climate of the Earth, we can start focusing on the different phenomena we have discovered so far and how they affect the climate here on Earth.
Solar Granules
Much like the bubbles in boiling water rising to the surface, these “granules” that we have named make up the bubbles that form the texture of the surface of the Sun (also called the photosphere). However, where bubbles are pockets of gas within a liquid, these granules are merely “hotter” spots of super-dense, extremely hot-plasma rising to the top and pushing their way past the “cooler” granules that get pushed back below the surface, only to heat up and race to the top once again. In fact, it is this process of heating and rising followed by cooling and falling, then repeating that facilitates the transfer of heat and light from the center of the Sun to the outer surface.
It’s hard to think about the incredible size of our Sun in terms that everyone can comprehend. The human mind is just not set up at a biological level to easily conceptualize values and objects in that grand scale. Think about it…what is the evolutionary advantage to thinking about huge things? Nevermind…I’m digressing. My point is that when you think about a normal bubble in terms of boiling liquid, you generally assume these bubbles are a few inches, maybe a few feet in diameter, right? Well…here’s an image of these granules when compared to North America. Remember, each of these bubbles is rising to the surface and falling every few seconds, hard to imagine as it is.
Image of solar granules courtesy of Wikipedia.org and NASA
Sunspots
Sunspots were first explained by Joseph Henry in 1848, who surmised by looking at a projection of the sun on a large white screen that these “darker areas” were regions of cooler material than the surrounding surface. We knew from taking observations for years that sunspots appeared and disappeared over time, moving slowly over the surface of the Sun and usually lasting between a few days to a few weeks. However, it wasn’t until the Solar and Heliospheric Observatory (SOHO) satellite was launched in 1995 that we started to truly understand the mechanics behind sunspots.
Image of this sunspot courtesy of APS.org
The surface of the sun is made of extremely hot plasma, which is to say a gas that is heated to the point that electrons do not bind to the nuclei in an atom. Instead, the entirety of the Sun exists in a state of atomic nuclei and electrons floating around in a soup that is denser than almost any material we have here on Earth. In this state, the nuclei and electrons are free-roaming charges that are pulled by electric fields, twisted by magnetic fields, and generate more magnetic fields as they move and churn throughout the Sun’s surface. In certain spots within the bubbling surface, the magnetic fields become too mixed up and tangled that the nuclei themselves are forced to slow down, literally ensnared within each other’s swirling magnetic fields. In the process of the nuclei slowing down, the macroscopic effect is that the plasma material itself cools by about 500 Kelvin to 2000 Kelvin. This overall cooling process solidifies the material (relatively speaking, not an actual solid), which solidifies the tangled magnetic field in place. Rather than sinking below the surface, the intense and solidified magnetic field at the sunspot actually makes the cooling problem worse. Much like traffic in a major city the more chaotic and hectic the traffic is, the slower people typically have to drive to compensate. This effect continues stacking on top of itself, cooling and entangling…cooling and entangling…again and again all the while making the sunspot larger as it coasts across the surface of the Sun entangling an ever more contorted magnetic field.
Well, as it turns out, the laws of physics have a way of really hating huge twisted magnetic fields. In fact, the electromagnetic force acts in such a way that is will exhort a force on any object it needs to in order to “smooth out” very twisted magnetic fields, and the more intense the magnetic field, the more intense the force…so you can guess where I’m going with this.
Up until now, I’ve only explained where sunspots come from, and I’ve already established that they disappear…so what happens to them when they “go away?” All of that twisted magnetic field embedded into the sunspot exhorts a twisted, chaotic force on the sunspot material as well. The larger and more complicated the sunspot gets, the more the force grows and twists along with it. Think of it kind of like twisting bubble wrap…you can twist it, but only so far and then POP! The bubbles are released and the bubble wrap loses its shape (and fun). Eventually, so much energy from the electromagnetic force is stored within the material of the sunspot that even its incredible weight and gravitational hold isn’t enough to keep it together. This release usually happens in a catastrophic explosion that is incredibly powerful and many times the size of our planet. Such an event usually triggers an extremely bright flash, called a solar flare, and if large enough, can also release solar prominences, or even a coronal mass ejection.
While sunspots themselves are essentially harmless to our climate and our health, they are the process by which other, more detrimental events such as solar flares are formed and therefore have been a topic of study and interest.
Faculae
Unlike the darker regions of cooler matter that make up the sunspots, the bright areas between the granules of the Sun’s surface are often birthplaces of brighter spots, called solar faculae. The term is Latin for “little torch,” which basically defines what these small bright spots look like. Similar to sunspots, faculae are temporary, but can last several days to several weeks. They also travel slowly across the surface of the Sun and can grow in size and change shape as they travel. Although on average the faculae are hotter than the rest of the surface of the sun and emit vastly more light, they typically do not affect the overall output of the Sun to have any noticeable effect on Earth’s climate. However, it should be noted that it is theoretically possible for many of these faculae to be present on the surface at once, making the sun notably brighter than normal for extended periods of time. Just because it hasn’t happened to a degree that we have noticed it doesn’t mean it can’t happen.
Image of solar faculae courtesy of nasa.gov
Solar Flares
Solar flares are extremely intense bursts of light that can last from several minutes to a few days. They usually emerge at or near sunspots that have burst and released their energy. It’s not uncommon for a solar flare to accompany a solar prominence or a coronal mass ejection as well, as when sunspots burst, a violently powerful amount of twisted magnetic energy is released, equivalent to the force of millions of nuclear bombs being detonated all at once. It’s not uncommon for the intensity of a momentary flare to be so intense that it rivals the output of the entire Sun as it releases.
Image of solar flare taken in the x-ray spectrum, courtesy of Wikipedia and NASA
To simply describe a solar flare as an intense flash is like describing the ocean as “a lot of water,” and isn’t accurately depicting the sheer awe involved in this event. The flare itself isn’t so much a bright light as it is a massive shockwave of electromagnetic (EM) energy traveling out of the Sun. This shockwave is so intense that it slams into random gas particles in space on its way, ionizing and superheating them to the point that even the particles themselves release their own x-ray radiation. Since the x-rays are also just a high-frequency form of EM energy, the wave essentially builds on itself, growing in intensity as it sweeps outward. Much like a small ship getting thrashed mercilessly about in a hurricane, the shockwave slams into our atmosphere, ionizing it as well, causing our own atmosphere to emit harmful radiation.
The effects of such an event are varied and devastating. The increased radiation on the upper atmosphere has shown to cause thermal expansion of the atmospheric drag boundary. As a result, some of the lower-orbit satellites in operation at the time recorded increased atmospheric drag, and some as a result had to adjust their orbits to compensate. At the same time, the increased EM radiation bombarding the atmosphere from the shockwave creates so much interference that radio-based long-range communications are typically interrupted. Since all EM radiation consists of oscillating electric and magnetic fields, the oscillating magnetic fields travel across the planet wreaking havoc on the power grid. Currents are induced where and when they aren’t supposed to be, and transformers can blow, wires can overheat and melt, even sensitive electronics can be fried. Anyone standing outside or in direct sunlight during such an event would be exposed suddenly to an unhealthy burst of hard and soft UV, x-ray, and even some gamma radiation. Prolonged exposure during an intense flare could definitely cause severe sunburns (worse than normal) followed by an increased chance of melanoma years later.
In March of 1989, a solar-flare event occurred that caused all of these effects mentioned, in addition to knocking out the Toronto Stock Market. The event was so costly and devastating that as a result, a joint venture between NASA and the European Space Agency sought to focus the next six years on the Solar and Heliospheric Observatory (SOHO) satellite. It is a laboratory in orbit devoted toward nothing but staring at the Sun constantly watching out for other such events.
Solar Prominences
Solar Prominences are the large, swirling loops and flames that appear to be occasionally burning off the Sun’s surface. Although resembling fire in appearance, these huge “flames” are actually made of extremely heated ionized gas, much closer to what you would find in a neon sign.
Image of a neon sign in London created by Tim Etchells
Scientists are able to deduce the material of the prominences by using the known property that ionized gas changes shape and moves when subjected to a magnetic field in a predictable way. Those prominences that would occasionally appear as enormous loops expanding outward from the surface don’t respond like any chemical-reaction based flame like we are aware of (i.e. like fire). Instead, however they respond more like the loops and bands that one sees within the lines of an intense magnetic field.
Image of large prominences courtesy of Wikipedia
IT’s hard to believe, but these enormous flames are many, many times the size of even Earth. Extended out in these loops, temperatures can rise to that of the corona, in the millions of Kelvin, enough to incinerate and burn away an entire planet in the blink of an eye. And yet, despite their incredible size and temperature, when looking at prominences from the standpoint of affecting Earth’s climate, they’re completely harmless. Even though the SOHO satellite has witnessed and recorded these events extending as far out from the Sun’s surface as a half a million kilometers, this is still nowhere close to the distance in which Earth orbits.
Much like solar flares, prominences are temporary phenomena that last anywhere from a few minutes to about a day or two. Some stable prominences that release a lot of stored magnetic energy have been observed to last for several weeks, however.
Coronal Mass Ejections
Coronal Mass Ejections (CMEs) are actually much scarier than they sound. They are essentially the resultant shockwave of stellar material and plasma that is created when a sunspot of large enough size tears itself apart. CMEs typically accompany solar flares and are what their name implies. They are large bodies of incredibly dense and hot mass that is ejected by the blast from the solar flare into the Sun’s corona.
Time-lapse footage of Coronal Mass Ejection, Courtesy of NASA.
CMEs can be extremely devastating toward life on our planet. In addition to the effects discussed with the accompanying solar flare, the charged cloud of particles that make up the mass of the CME bombards our planet, charging it with electric potential causing degradation to Earth’s magnetic field. Such an event can actually disrupt and counteract portions of the earth’s magnetic field temporarily, exposing the surface to harmful radiation from the CME, electronics, avionics, even navigational equipment such as compasses might not work correctly or fry entirely. In 1989, when a solar flare was accompanied by a CME, the aurora borealis (northern lights), which are bright energetic disruptions in our atmosphere, were seen as far south as Texas.
Even with all of these effects, we were lucky. CMEs aren’t like solar flares in the sense that they aren’t made of light. Instead, they consist of millions of cubic kilometers of extremely high-energy gas. From a physics standpoint, that much mass traveling that fast is very similar in concept to a bullet fired from a gun.
A ludicrously big gun.
However, thanks to the chaotic nature of the Sun’s surface, the locations and sizes of the sunspots are always changing. From what we’ve seen, the sunspots seem to be the sources of the CMEs, so as each sunspot passes by the center if the sun, the trajectory of each possible CME sweeps past us. So rather than a single dangerous point sweeping by occasionally, in reality, there are always several dangerous points sweeping past at any given time.
You feeling lucky?
In 1989, the Earth was only grazed by the CME that caused all of the disruptions and the geomagnetic storm. There’s no telling what kind of real damage could be done to our climate if we were to take a direct impact. Since sunspots and CME events are occurring all the time, on all parts of the Sun’s surface, it’s not an “if” but a statistical “when” we will be hit be one of these devastating blasts.
So what have we as a society done to address these kinds of events? If not to prevent them (as that’s really not possible), then at least to prepare ourselves in the event one occurs or shield our sensitive equipment? Well, believe it or not, during the 1989 event, even military operations were obstructed and communications were jammed by the geomagnetic storm. The military has always been an organization that doesn’t like getting caught with its pants down, so a rather sizable response was mustered to handle the study of the Sun.
The NASA-ESP joint project SOHO satellite was launched in 1995 for the purpose of studying the sun and monitoring it in multiple spectra, allowing scientists to have a better means of observing and understanding the Sun and solar phenomena. The satellite proved to be invaluable to researchers and transformed our society’s understanding of how the Earth and Sun are related.
In 2003, NASA prepared and launched its next satellite, the Solar Radiation and Climate Experiment (SOURCE) satellite. This satellite was designed to monitor the lighting conditions here in orbit around Earth. The data from this satellite allowed scientists to take more accurate measurements focused on the spectrum and intensity of the Sun’s output from orbit, where atmospheric effects aren’t able to add uncertainty to the results.
Most recently in 2006, NASA has launched a pair of twin satellites, called STEREO (for Solar TErestrial RElations Observatory), designed to orbit around the Sun, in the same orbit as Earth. The two satellites are meant to lead ahead of and trail behind Earth, taking continual photographs and measurements from two different perspectives, allowing scientists to get a much clearer idea of how the weather on the Sun affects the climate here on Earth.
