A coronal mass ejection (CME) is a huge bubble of electrified gas ejected from the Sun. The ejection of this material can occur over the course of several hours; traveling at a speed of 1000 kilometers per second, the energetic particles of a CME can take a day or more to reach the Earth. CME’s are often associated with filaments, arching loops of gas supported by magnetic field lines. A filament appears as a prominence when viewed on the limb of the sun. Since filaments are not necessarily associated with sunspots, CME’s can occur even when the sunspot cycle is at a minimum [7]. However, the frequency of CME’s generally corresponds with the sunspot cycle.

A more benign and definitely more enjoyable result of the interaction between the highly energized particles of a solar flare or CME and the Earth’s magnetic field are aurorae. An aurora occurs when particles from the sun are excited or ionized from spiraling down into the Earth’s magnetic field near the poles. The resulting release of energy can be seen as visible light of varying colors and intensities. Typically, aurorae can be seen in the region within 20° of Earth’s magnetic poles, but on rare occasions they can be seen as far as 40° degrees away from the poles (Fig. 6).

Figure 6
Rare red aurorae occur much higher in the atmosphere (300-500 km) than the more common green aurorae. The red light is emitted by oxygen atoms as they interact with the influx of electrons and protons from a solar flare or CME. Photograph taken by the author in Socorro, New Mexico on 01-03-30.