Also, today is the anniversary of a small space weather outage in Canada. On August 16, 1989 the Toronto stock exchange was disabled by a geomagnetic storm. This followed on the massive outage in March 1989 that interrupted electrical distribution throughout Quebec. This geomagnetic storm was caused by a coronal mass ejection from a very large X20 solar flare seen on August 16, 1989, which was even stronger than the X15 flare on March 6, 1989 that heralded the earlier storm.
Microchips failed in August 1989 rather than the electrical grid. It affected many fewer people than the 6 million who were left without electricity in March. But it shows the many ways that space weather affects our society. What about the current solar cycle, #24? The Sun appears to have reached peak activity for Solar Cycle 24 in its northern hemisphere. The south continues to produce more and more sunspots. During the decline of a solar cycle the sunspots tend to last longer and the coronal mass ejections can cause large geomagnetic storms. Even though large flares are the heralds of violent space weather, it is the geomagnetic storms that interfere with power grids.
Solar Cycle 24 continues to follow the path of a below average cycle. It is also the best-studied solar cycle, with SDO, SoHO, both STEREO spacecraft, Hinode and numerous ground-based telescopes watching this cycle grow. We study the Sun to know when space weather happens and to learn how to predict it. The images from AIA and HMI are just the beginning of the science of SDO!
