Have scientists seen changes in the intensity of space weather?
Yes; sunspots, for example, change in intensity over an 11 year cycle. When solar flares occur, space weather activity increases dramatically. At present, we are in the increasing phase of Cycle 23, which began in October 1996 and is expected to peak sometime during the year 2000. SEC scientists have noted a steady increase in the number of sunspot groups and solar flares, as well as other space weather occurrences like solar proton events and a rising 10.7 cm solar radio flux. We’ve had about a dozen episodes of intense space weather so far this cycle and we expect to see many more as Cycle 23 continues.
On a short time scale, the intensity of space weather is always changing. Conditions can be mild one minute and stormy the next. On longer time scales, space weather varies with the solar cycle. The solar cycle is an average 11 year cycle where the number of sunspots goes from very few per month, to many, and back to very few. At solar minimum, we might see no sunspots where at solar maximum, we can have 200 sunspots in a month. Solar flares, coronal mass ejections and solar energetic particles all increase in frequency as we get closer to solar maximum. High speed wind streams are more frequent at solar minimum, thus ensuring that space weather is something to watch for no matter where we are in the solar cycle.
