March 2, 2013
Low Solar Activity May Mean Current Solar Cycle Will Have Two Peaks
redOrbit Staff & Wire Reports - Your Universe Online
While 2013 is supposed to be the year of Solar Max - the peak of the 11-year sunspot cycle - the relatively low solar activity recorded thus far has led experts to conclude that an unusual phenomenon has occurred. This most recent solar cycle has had not one but two peaks.
According to NASA, sunspot numbers during the months of January and February 2013 were well below values recorded back in 2011. Furthermore, they report that strong solar flares have been infrequent for the past several months.
While those observations have led some to question whether or not forecasters were incorrect in their predictions for this year, officials from the Goddard Space Flight Center say that there is an explanation.
"This is solar maximum, but it looks different from what we expected because it is double peaked,” Dean Pesnell, a solar physicist at the Maryland-based research laboratory, explained Friday in a statement.
“Conventional wisdom holds that solar activity swings back and forth like a simple pendulum,” the US space agency added. “At one end of the cycle, there is a quiet time with few sunspots and flares. At the other end, Solar Max brings high sunspot numbers and solar storms. It´s a regular rhythm that repeats every 11 years.”
However, that is simply not the case. Astronomers who have tracked sunspots for several centuries have observed that the solar cycle does not follow a perfect pattern. The cycle itself can actually take between 10 to 13 years to complete, and amplitude variations that occur during the process can make some Solar Max events stronger or weaker than others. Furthermore, at times there can actually be more than one peak.
"The last two solar maxima, around 1989 and 2001, had not one but two peaks,” Pesnell said. During those periods, there was an increase in solar activity, then a decrease, and then another increase — a “mini-cycle” that lasted approximately two years, according to NASA.
It is possible that this phenomenon could be occurring now, as the number of sunspots increased in 2011 but decreased the following year. Pesnell said that he expects the count to rise again later on this year, and that this second peak could possibly last into 2014.
“Another curiosity of the solar cycle is that the sun's hemispheres do not always peak at the same time,” NASA explained. “In the current cycle, the south has been lagging behind the north. The second peak, if it occurs, will likely feature the southern hemisphere playing catch-up, with a surge in activity south of the sun's equator.”
The NOAA/NASA Solar Cycle Prediction Panel, a team of solar physicists (including Pesnell) who gathered in 2006 and 2008 to forecast the next Solar Max, predicted that the current solar cycle would be of below average intensity and that solar maximum would occur this May.
“Given the tepid state of solar activity in Feb. 2013,” NASA says the chances of that happening “now seems unlikely.”
"We may be seeing what happens when you predict a single amplitude and the Sun responds with a double peak," Pesnell added.