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LAS CRUCES, NM -- The sun is entering a period of inactivity the likes of which have not been seen in 300 years, a prestigious panel of solar scientists said yesterday, and that could mean significantly colder temperatures for planet Earth in coming decades. Lower sunspot activity also creates a more hospitable environment for communications and space exploration.
Three lines of research presented at the annual meeting of American Astronomical Society's Solar Physics Division agree that the sun is entering a state of sunspot quiescence last seen during the Maunder Minimum, 1645-1715, a period in which the sun was nearly spotless.
The Maunder Minimum is associated with an historical period known as "The Little Ice Age" during which temperatures in Europe plummeted to unusually low levels. "The fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation," said Dr. Frank Hill, associate director of the National Sunspot Observatory.
A panel of solar scientists in 2009 predicted the sun would produce fewer spots than expected for the current cycle, cycle 24, based on the sunspot activity of previous cycles. That panel predicted a maximum of 90 sunspots when 120-150 might have been expected, and the new reports indicate that cycle 25 may not even happen. Estimates for the current cycle now range from 60 to 80 sunspots, Hill said in a telephone interview prior to yesterday's news conference.
"We expected to see the start of the zonal [magnetic] flow for cycle 25 by now," Hill explained, "but we see no sign of it. This indicates that the start of cycle 25 may be delayed to 2021 or 2022, or may not happen at all."
The evidence on which the scientists base their conclusion includes:
A jet stream, inside the sun and visible on the surface, associated with the solar cycle should be visible now for cycle 25, but it is not.
A light intensity in the solar corona -- the sun's "atmosphere" in which, the Earth is embedded on the extreme edge -- also tracks the solar magnetic field, and should be -- but is not -- showing what is called a "rush to the poles," a movement from the lower solar latitudes to the polar regions culminating in a reverse in the polarity of the sun's magnetic field. "It is possible a rush to the poles does not exist in this solar cycle," Dr. Richard Altrock said during today's news conference. Altrock manages the Air Force's coronal research program at NSO's Sunspot, NM, facilities.
The magnetic field strength of sunspots has been weakening for 13 years, while becoming brighter, and if extrapolated, that trend would result in no sunspots being visible in the years 2021 or 2022.
Scientists have long noted that variations in solar radiation (referred to as "total solar irradiance" or TSI) affect surface temperatures on earth, and a group of Chinese scientists publishing in the February issue of the journal Annales Geophysicae identified the characteristics of solar cycle 24 as being "helpful for the study of the relationship between global warming and variation of solar activity, namely the contribution of variations in TSI to global warming."
However, the Chinese scientists say, "The probability of the Sun entering a new Maunder minimum is rather low at the present time."
"There's been a lot of controversy as to how much the sun contributes or not to global warming or global cooling," Hill said, "and I am basically agnostic on that, in that I remain to be convinced one way or the other. So if this prediction [about the sun entering Maunder Minimum conditions] is true and we really do not have sunspots for an extended period of time, we will have a splendid opportunity to test those hypotheses."
