If you have an interest in astronomy, or follow those "end of the world" blogs, you've probably heard about solar flares, and the potential impact of extreme events on the earth. Solar flares are associated with sunspots, are a regular feature of the Sun, and are normally not something to be worried about. However, due to solar cycles, about every 11 years or so there is a period of increased sunspot activity which can result in flares which actually have an impact on the earth. Recently we have heard stories of potential doom, including worldwide power outages and GPS satellites being knocked out. The next solar maximum will be about 2025. Should we be worried?
Well, yes and no. Most of the concern revolves around the potential for a very strong solar flare which could potentially overload transformers and cause widespread, and possibly permanent power outages. This is a real threat, and was described recently in a National Academy Of Sciences report. In particular, a repeat of a very large flare which occurred in 1859 (known as the Carrington Event) could, according to the report, cause an electromagnetic overload of power grids, cause transformers to explode, with damage that might not be repairable for 5-10 years. Now, the Carrington Event appears to be quite unusual, and most solar events are much less spectacular. But it should be on our preparation radar. Smaller scale events can still cause regional outages (such as in 1989, when a solar flare resulted in a widespread outage in Quebec, lasting 12 hours and affecting 5 million people)
Fortunately, we have some wonderful resources available, especially from the NOAA Space Weather Prediction Center which, like its terrestrial counterpart, offers warnings of activity that could cause problems. However, to be able to use these warnings and resources, we need a quick lesson in solar flares. Here is the super-quick version: for a more detailed account see the SWPC FAQ. Basically, sunspots can result in solar flares which are intense bursts of electromagnetic radiation. These only really affect the earth if the sunspot is pointing right in our direction. The most immediate impact of these earthbound flares is a very quick increase in X-ray flux. You can see X-ray flux values in this plot from the NOAA GOES satellite (live version available on the SWPC site):
See the letters on the right (A, B, C, M, X)? That represents the intensity of the flare. The really interesting ones are "X" class flares, and we get a few of these each solar cycle. Very quickly after the flare an X-class (and sometimes an M class) can cause shortwave radio outages on the sun-facing side of the earth. These rays reach the earth very quickly. The possible impacts on radio are given by the R scale on the NOAA Space Weather Scale
A solar flare can also produce a Coronal Mass Ejection
(CME). This is a cloud of geomagnetically charged particles which reaches earth usually a couple of days after a flare. This is the one which can cause power outages. It is measured using Planetary K-index (Kp) values - you can see Kp values in the plot below (also taken from the NOAA site):
Anything over "4" is classed as a storm, although it's really 8's and 9's which spell trouble. Again for a mapping to real effects, see the G-scale on the NOAA Space Weather Scale.
So that's the quick intro to get you started! For more information, as well as the NOAA site, I recommend SolarHam.com
(check out the forums) and SpaceWeather.com
. You can track current solar events in the AllHazards Dashboard
and we give weekly updates on solar weather in the Threat Analysis Briefing
Adapted from an article originally published in allhazards.blogspot.com