The Corona and Solar Activity

As we have discussed, the Sun goes through an activity cycle that is correlated with observables like the number of sunspots. The appearance of the corona has a very strong dependence on this cycle, as illustrated in the following two images.

The left image was obtained during a period of high solar activity and the right during a period of relatively low solar activity. Notice the fundamentally different appearance of the corona. The corona during the active Sun period shows many streamers at all angles around the disk of the Sun, while the corona during the quiet Sun period shows larger bottle-shaped streamers (called helmet streamers because of their capped appearance) concentrated in latitudes near the equator.

The following false-color image was taken with the Large Angle and Spectrometric Coronagraph (LASCO) on board the SOlar and Heliospheric Observatory (SOHO). It shows rather graphically the streamers in the solar corona.