Aurora borealis at Sanford Seacoast Regional Airport last May
Photo: Wyatt Worcester
We May Be in for a Real Light Show
By Kevin McKeon, Maine Master Naturalist
The night sky lights up with dancing streaks of pinks, greens, blues and reds, showing us folks in the upper Northern Hemisphere the wonders of the aurora borealis, or northern lights. As we approach the March 20 spring equinox, astronomical conditions will align in such a way that it may be possible to view this skylit nighttime show in the Sanford area.
What makes all this “space weather” happen, and why is this phenomenon more highly expressed at certain times? It all starts with photons from the sun. The star in the center of our solar system is essentially an ongoing nuclear explosion called a solar dynamo — a rotating, disorganized, chaotic, tumultuous fiery mass in which electrons and ions have separated, creating a super-hot mix of electrically charged particles that form a state of matter called plasma. All this activity generates a magnetic field, similar to the magnetic field around Earth generated by its revolving molten, iron core.
And, like just about everything else, the sun has cycles, whereby the pulses of this fiery orb tend to follow an 11-year cycle of growing and ebbing energy levels called solar maximum and solar minimum. At solar maximum, high power levels cause the reversal of the star’s magnetic poles. The previous solar maximum was July 2014. So now, 11 years later, the building solar dynamo is reaching its maximum energy level and with it, the highest activity levels of the sun surface: sunspots, flares, and ejections.
As the cycle grows towards its maximum, the lines in the sun’s magnetic field become increasingly disorganized, sometimes twisting together to form magnetic blockages in the sun’s surface. These blockages can effectively prevent plasma’s heat from reaching the surface, causing relatively cool spots; these are sunspots. Pressure builds at the sunspot, eventually bursting through the sunspot with great energy. This could be seen as either a solar flare or a coronal mass ejection. The relatively smaller flares appear as beams of light. Ejections appear as huge waves of plasma. Both can cause auroras by their interactions with Earth’s atmosphere.
Another factor involved with appearances of auroras, and also at its peak during solar maximum, is solar wind. These energy waves are released by the sun’s plasma at varying speeds reaching over 1 million miles per hour, carrying electrically charged, high energy particles called photons and electrons throughout our solar system, and dragging the sun’s magnetic field with it. As these magnetic particles reach Earth, our planet’s magnetic field “captures” them — like a magnet capturing a small steel ball. The particles then travel along the Earth’s magnetic field lines into its upper atmosphere. The atoms and molecules in the atmosphere get bombarded by these particles, causing the release of this high energy which manifests as various colors — the auroras!
Now, for the interesting factor that could impact the Sanford area’s viewing of the aurora. At the spring and fall equinoxes, the Earth’s and sun’s poles are parallel. This alignment causes the sun’s high energy particles to hit Earth’s magnetic field (the magnetosphere) at a direct angle, allowing more of these particles to be captured by Earth’s magnetosphere, creating geomagnetic storms during which the auroral ovals expand from Earth’s poles towards the equator. Also, the sun is currently at solar maximum in its 11-year cycle so is releasing more particles with more energy that bombard more of Earth’s atmospheric molecules and atoms. All this creates more color over a larger area.
Factors determining the colors of the aurora are the chemical composition of the atmospheric atoms and molecules, the level of molecular “excitement” caused by the energy bombardment, and the distance from our eyes to the bombardment. Sometimes auroras can appear whiteish. A digital camera is more sensitive and better able to discern color discrepancies, so capturing a digital image may reveal the colors in that funny looking, wavering light gray cloud in the nighttime sky.
Video, flare and coronal mass ejections (CME): https://svs.gsfc.nasa.gov/11667/
Editor’s note: Did you see something unusual last time you were out in the woods? Were you puzzled or surprised by something you saw? Ask our “Out in the Woods” columnist Kevin McKeon. He’ll be happy to investigate and try to answer your questions. Email him directly at: kpm@metrocast.net
The post Out in the Woods appeared first on Sanford Springvale News.
