2017-07-18 13:27:44.000 – Jillian Reynolds, Summit Intern
Also known as “Northern Lights”, the Aurora Borealis is one of Nature’s greatest spectacles. It is the result of electrons colliding with the upper parts of the Earth’s atmosphere (NOAA, 2017). The electrons are energized through acceleration processes in the downwind tail of the magnetosphere. The accelerated electrons follow the magnetic field of Earth down to the Polar Regions where they collide with oxygen and nitrogen atoms and molecules in Earth’s upper atmosphere (NOAA, 2017). In these collisions, the electrons transfer their energy to the atmosphere thus exciting the atoms and molecules to higher energy states. When they relax back down to lower energy states, they release their energy in the form of light. When oxygen atoms are excited, they emit red and green light (NESTA, 2012). Excited nitrogen molecules emit red, blue, and violet light. You can expect to see the brightest lights during the nighttime, with clear skies, and with little to no light pollution.
Earth’s magnetic field guides the electrons such that the aurora forms two ovals approximately centered at the magnetic poles (NOAA, 2017). During major geomagnetic storms these ovals expand away from the poles such that aurora can be seen over most of the United States. One indicator of the magnitude of a geomagnetic storm is called the Planetary K-index (Kp-index). The Space Weather Prediction Center (SWPC) uses the K-index to decide whether geomagnetic alerts and warnings need to be issued for users who are affected by these disturbances (SWPC, 2017). K-index Warnings are issued when NOAA estimates Kp-indices of 4-7. K-index Alerts are issued when NOAA estimates Kp-indices reach 4-9. Stronger geomagnetic storms can start to disrupt satellite and radio communication.
Up here on the summit, we did have a chance to see the Aurora this past Sunday night. The Observatory crew and I kept checking the weather for after sunset and how strong the geomagnetic storm was throughout the day. We have received some Warnings issued from NOAA for the Kp-indices earlier in the day. Some of us stayed up late and went up to the observatory deck to keep an eye on the sky. The sky conditions were mostly clear and we could see stars. Unfortunately, we were unable to see the Aurora that night. One of the reasons for this was that the strongest levels of Kp-indices were seen before sunset (as seen below). It was still too light out to see anything. We were all upset, but are still hoping to see the Aurora some other night before the summer is over!
Jillian Reynolds, Summit Intern