There were many times I've viewed pictures of the night sky filled with waves of green, pink, and purple light. Most likely you have asked yourself "what's really going on" up there. The beautiful display we call the aurora borealis (or northern lights) has been a source of myth and legend for generations. There isn't much magic about it; there aren't even angry gods. The story begins with our Sun.

Our Sun is always spewing out small bits of itself into space. The stream of charged particles (mostly electrons and protons), known as the solar wind, moves outward to distances of millions of miles before colliding with Earth's magnetic field. For humans, fortunately, that field functions as a large shield deflecting most of the solar wind. However, near the North and South poles, Earth's magnetic field weakens, allowing some of those solar particles to enter our upper atmosphere via the magnetic field lines. Once in our upper atmosphere, those particles collide with gas molecules such as oxygen and nitrogen. When these particles do collide, they transfer their energy to those gas molecules, which then emit that energy as light. Think of it like a neon sign - each gas produces its own color. At higher altitudes, oxygen tends to produce red light while at lower altitudes oxygen produces greenish light. Nitrogen is responsible for producing blue and purple light. Overall, it is a massive light show produced by the power of the Sun - 93 million miles away.

When can you watch this spectacle? To see this spectacular sight you need to be located in extreme latitudes where there are fewer city lights. The Northern Hemisphere provides locations such as Alaska, northern Canada, Iceland, Scandinavia, and Russia. The viewing period occurs from mid-August until early April due to the longer darker nights. Additionally, viewing requires clear skies; clouds may spoil your view regardless of the intensity of the aurora. Finally, during the two equinoxes in September and March, the viewing period coincides with periods when the solar wind strikes Earth at nearly ideal angles.

Additionally, timing is everything. The solar wind reaches Earth at a greater rate when the sun is closer to solar maximum (a point approximately every 11 years). As we approach another solar maximum within the next couple of years, now would be an excellent time to begin planning your trip.

Ultimately, the aurora borealis reminds us that Earth is not isolated - rather it interacts continuously with the Sun in terms of both particles and magnetic fields. If you're fortunate enough to witness a glowing wave of green, you'll know you're witnessing the solar wind greeting the upper atmosphere - a very interesting concept.