After the long nights of December and early January, the sun's northward motion is bringing longer days to the Adirondacks, beginning to awaken the land from its winter slumber, starting with the "hey, sweetie" calls of the black-capped chickadees.
But this year, the sun is also waking up from a deeper than expected slumber of its own.
There are once again spots on the sun after years of its face being nearly blank. This is good news for those of us who revel in displays of the Aurora Borealis, though it could be bad news for satellites and electrical grids.
The sun is a nuclear explosion contained by gravity. In its core, the intense heat and pressure causes hydrogen nuclei to fuse into helium nuclei. The helium nuclei have 0.7 percent less mass than the original hydrogen nuclei because the fusion process releases it as energy as described by Einstein's famous equation: E = mc2 where E stands for energy, m for mass and c is the speed of light, 300,000 km/s or 186,000 miles/sec. Because the speed of light is so big and squaring it makes it even bigger, an utterly huge amount of energy is released when matter is converted. Every kilogram of hydrogen the sun converts to helium (a kilogram is the mass of a 1 liter bottle of water) produces 175 million kilowatt-hours of energy the source of sunshine!
Since the sun is an ongoing explosion, one would expect stuff to be flying off of its surface, and indeed, the sun produces a "solar wind" of charged particles blown off its 10,000 degrees F surface at about a million miles an hour.
The Earth's magnetic field usually deflects this spray of particles harmlessly around the planet. But sometimes, particularly strong bursts of particles penetrate into our atmosphere and reveal the explosive power of the sun as displays of Aurora Borealis and Australis. These strong bursts are associated with sunspots. Seen as dark areas on the face of the sun sunspots are slightly cooler than the surrounding surface. Though the exact mechanisms for their formation are not yet fully understood, we do know them to be caused by magnetic loops emerging from the surface.
I describe these to my students as magnetic hernias. Since charged particles follow magnetic fields, those on the surface of the sun shoot up along the loop, cooling and darkening the area at the base. Sometimes, particles burst completely off the sun in Coronal Mass Ejections, or CME's.
When these bursts collide with Earth's magnetic field, it steers the charged particles to the poles where they collide with molecules in the atmosphere, causing them to emit light.
The number of sunspots varies over a fairly regular cycle of about eleven years as shown in Figure 1. The period during the second half of the 17th century when there were almost no spots is known as the Maunder Minimum and correspond to "The Little Ice Age," when the climate was particularly cool. Evidence is emerging that the cooling may have primarily been due to volcanic eruptions in Indonesia, but some hold that the lack of sunspots indicated a cooler sun, enhancing the effect of the high-altitude volcanic ash. Since 1700, the sunspot cycle has been regular, though the heights of the maxima vary.
One of the reasons that President John F. Kennedy pushed us to go to the moon before 1970 was to make sure our astronauts were outside the Earth's magnetic field when the sun was quiet. In this century, the solar maximum of 2001 was anticipated with much excitement, including "Solar Max" playing in all the IMAX theaters. But it fizzled, as can be seen in Figure 2 where the number of sunspots fell off dramatically right at the expected peak. We did have more sunspots and some terrific auroral displays in 2003, but not the number that had been anticipated. Then the sun got very quiet. Too quiet for some. 2009 was so lacking in sunspots that some expressed concern that we could be entering another Maunder Minimum. In 2010, though, spots again began appearing on the sun and the number has been steadily growing.
The next maximum is predicted to occur in 2014. It's not anticipated to be one of the greater maxima, but our ability to predict the sun's behavior is still in its infancy, so we could be surprised! As we approach the maximum, listen for reports of solar storms.
Spaceweather.com is updated daily with the solar image, sunspot number and probabilities for aurora. You can even subscribe to receive phone or text alerts. I've had this service for a few months and find it a great way to keep up with the sky. If you see an aurora, it will most likely be a striated green or reddish glow toward the north. It will also pulsate for reasons too complex to explain here.
Keep in mind that it is due to a real-time interaction of million mile per hour particles with our planet's magnetic field and atmosphere it is a dynamic event with swift and beautiful changes. Since it is an electromagnetic phenomenon, it can have negative consequences for the power grid. In 1989 an auroral display darkened nearly all of Quebec, including Montreal. They have improved their power system to resist another 1989 event, but we could still get surprised.
A catastrophic solar storm like that the current predictors of the end of the world (on 12/21/2012) claim is not impossible, but unlikely. Some pretty aurora and perhaps a few limited power outages are the worst that any of us should anticipate.
If you have questions about the sun, aurora or any other astronomical topic, please visit the Adirondack Public Observatory web site at apobservatory.org or email Aileen at firstname.lastname@example.org.