Earth received a glancing blow from a coronal mass ejection (CME) this week, which created beautiful auroras, or northern lights, seen across northerly latitudes last night (October 8-9, 2012).
EarthSky Facebook friend Colin Chatfield observed the auroral display from Saskatoon, Saskatchewan, Canada. He wrote:
They started off very brilliant, but died down quickly. They appeared again, but not as bright as earlier. However, they were still nice. It was windy and clouded over quickly, so the show didn’t last too long.
The solar eruption that sent the CME hurtling toward Earth – ultimately causing last night’s display – happened late Thursday according to clocks in the U.S. (October 4, 2012). NASA said:
Not to be confused with a solar flare, which is a burst of light and radiation, CMEs are a phenomenon that can send solar particles into space and can reach Earth one to three days later. Experimental NASA research models show the CME to be traveling at about 400 miles per second.
In contrast, Earth moves around the sun at about 18 miles per second.
There is no danger to people on Earth from a passing CME, although these vast streams of charged particles from the sun can affect our technologies, for example, satellites in Earth orbit. Meanwhile, as the charged solar particles strike atoms and molecules in Earth’s atmosphere, they excite those atoms, causing them to light up. Those at northerly latitudes see the result as beautiful displays northern lights.
The colors in the aurora were a source of awe and mystery throughout human history. But science says that different gases in Earth’s atmosphere give off different colors when they are excited. Oxygen gives off the green color of the aurora. Nitrogen causes blue or red colors.
Bottom line: A coronal mass ejection or CME that left the sun on October 4, 2012 has interacted with Earth’s magnetic field, causing beautiful displays of the aurora, or northern lights, seen by many across northerly latitudes on the night of October 8-9.