Powerful solar flares could be better predicted by using the Sun's magnetic field as a “sundial”.
For 400 years, sunspots have been used to measure the solar cycle, but the recently proposed “Fifth Circle of the Sun” system could predict dangerous and violent solar events for years to come.
A new study, published in the journal Frontiers in Astronomy and Space Sciences, suggests that a “sundial” based on the Sun's magnetic field may be a more accurate way to predict dangerous solar flares that threaten Earth's communications systems for years to come.
Proposed by Partnership for Heliophysics and Space Environment Research (PHaSER) scientist Robert Limon, the new structure is based on research that indicates marked and sometimes dramatic changes in the solar cycle occurring with the rhythm every fifth part of the cycle.
Calling the frequency “The Fifth Circle of the Sun”, Limon and his team believe that while solar cycles can vary across months or even years, they still operate with a clear and predictable sequence of events.
If correct, the concept of a “sundial” could replace the current method used to measure the solar cycle: sunspot observations, which has been around for four centuries.
The sun has an approximate solar cycle of 11 years, with a reduced solar activity (solar minimum) is used to determine the beginning of each cycle. Lemon believes this method of tracking solar cycles is arbitrary and inaccurate. His new concept is based on a study published two years ago that pointed to the existence of a phenomenon in the solar cycle, which the authors called the “terminator”.
Limon and his colleagues used data collected by the Dominion Radio Astrophysical Observatory in Penticton, Canada, and the Wilcox Solar Observatory at Stanford University to determine patterns in the solar cycle.
“How many different solar objects can we watch? And then we realized that they all intersect in the same set of fifths,” Limon said.
They found that the changes occur in exactly 1/5 of the cycle. During cycle 2/5, dark regions form at the Sun's poles, known as holes in the polar corona. At 3/5, the Sun fired the last X-class flare of this cycle, a powerful and potentially dangerous solar flare. At the same time, in 4/5 cycles, sunspots in the solar photosphere reach a minimum. Then, the final event of the cycle, the sun passes through another “terminator”.
The scheme proposed by Limon and colleagues suggests that the current solar cycle began in December 2021 and will end in mid-2027.