The next 11-year cycle of solar storms will most likely start in March 2008 and peak in late 2011 or mid-2012—up to a year later than expected—according to a forecast issued by the NOAA Space Environment Center.
During an active solar period, violent eruptions occur more often on the sun. Solar flares and vast explosions, known as coronal mass ejections, shoot energetic photons and highly charged matter toward Earth, jolting the planet’s ionosphere and geomagnetic field, potentially affecting power grids, critical military and airline communications, satellites, Global Positioning System signals, and even threatening astronauts with harmful radiation. These same storms illuminate night skies with brilliant sheets of red and green known as auroras, or the northern or southern lights.
The NOAA Space Environment Center led the prediction panel and issued the forecast at its annual Space Weather Workshop in Boulder, Colo. NASA sponsored the panel.
Expected to start last fall, the delayed onset of Solar Cycle 24 stymied the panel and left them evenly split on whether a weak or strong period of solar storms lies ahead. Neither group predicts a record-breaker.
Scientists measure solar cycle intensity by the maximum number of sunspots—dark blotches on the sun that mark areas of heightened magnetic activity. The more sunspots there are, the more likely it is major solar storms will occur.
In the cycle forecast, half of the panel predicts a moderately strong cycle of 140 sunspots, plus or minus 20, expected to peak in October 2011. The other half predicts a moderately weak cycle of 90 sunspots, plus or minus 10, peaking in August 2012. An average solar cycle ranges from 75 to 155 sunspots. The late decline of Cycle 23 has helped shift the panel away from its earlier leaning toward a strong Cycle 24. Now the group is evenly split between strong and weak.
The first year after solar minimum, marking the end of Cycle 23, will provide the information scientists need to arrive at a consensus. NOAA and the panel decided to issue their best estimate now and update the forecast as the cycle progresses, since NOAA Space Environment Center customers have been requesting a forecast for more than a year.
For related information, go to www.isa.org/environment.