Astrophysicist predicts unusually intense solar cycle

The sun has begun a new 11-year “weather” cycle, and scientists have very different ideas on just how much energy will be available to fuel its eruptions. The consensus view of an international panel of 12 scientists calls for the new cycle, Solar Cycle 25, to be small to average, much like its predecessor, Solar Cycle 24.

But a prominent astrophysicist at the National Center for Atmospheric Research, Scott McIntosh, foresees the sun going gangbusters. The cycle is already off to a fast start, coinciding with the recent publication of McIntosh’s paper in Solar Physics. The study, with contributions from several of his colleagues, forecasts the nascent sunspot cycle to become one of the strongest ever recorded.

The weather on the sun matters because solar outbursts can unleash radiation into Earth’s atmosphere that is dangerous for air travelers; interfere with spacecraft and satellites; and, in a worst-case scenario, inflict significant damage on Earth’s power grids.

The forecasts for the new solar cycle, which are so divergent, regard the number of sunspots that the sun will cook up over the coming 11 years.

Forecasting sunspots is important, since “coronal mass ejections” that originate from them can send disruptive bursts of magnetic energy toward Earth. The number of sunspots crowding the solar disk at one time varies significantly over the course of the solar cycle. During solar minimum — which we’re emerging from right now — weeks can pass without a single sunspot. But at the peak of a solar cycle, the average monthly sunspot number ranges from 140 to 220. Solar Cycle 24’s sunspot activity proved underwhelming — with the sunspot number averaging 110 at its peak.

An international panel co-chaired by scientists from NOAA and NASA, which featured six U.S. solar scientists and half a dozen from abroad, is anticipating a similarly quiet cycle 25. But McIntosh, who is now NCAR’s deputy director and previously directed its High Altitude Observatory, estimates a sunspot number more than double what the joint panel is predicting.

Among the diverse panel, disagreements often stemmed from the state of the science, Doug Biesecker, the panel’s co-chairman and a scientist at NOAA’s Space Weather Prediction Center, explained, and how poorly understood the underlying physics of the sun are.

“[Ultimately,] we concluded it would be similar in strength to the cycle that’s just died,” said Gordon Petrie, a scientist at the National Solar Observatory.