Scientists have been trying to determine the solar cycle using sunspots since humanity first
"Solar minimum", or a period of reducedsolar activity, has traditionally been used by scientists to mark the beginning of each cycle. However, R. Robert Limon, a fellow at the Partnership for Heliophysics and Space Environment Research (PHaSER), argues that the structure of the "solar minimum" is rather arbitrary and imprecise.
A recent study by Lemon,demonstrates that many significant changes during the solar cycle can be accurately described and predicted using a "sundial" based on the Sun's magnetic field rather than the presence or absence of sunspots. The new approach improves on the classic sunspot detection method by predicting bursts of dangerous solar flares or changing weather patterns for years to come.
New study published in the journalFrontiers in Astronomy and Space Sciences, demonstrates that the solar cycle functions as a single sequence of events. Every fifth part of the cycle there are noticeable, and sometimes abrupt changes. This is true no matter how long a given cycle actually is, which can range from a few months to a year. Lemon and his colleagues refer to it as the "circle of fifths" as a tribute to music lovers.
A new study by Limon and hisby colleagues Scott McIntosh of the National Center for Atmospheric Research (NCAR) and Alan Title of the Lockheed Martin Center of Excellence, is based on a 2020 published paper by Limon, McIntosh and Daniel Marsh of NCAR. This article demonstrated the existence of a solar cycle phenomenon that the research team has called the "terminator".
The Sun's magnetic field changes direction everysolar cycle, but there is overlap between successive cycles. "Terminator" just shows when the polar field of the previous cycle has completely disappeared from the surface of the Sun, and a sharp increase in solar activity quickly follows.
The new article points to additionalfeatures on the path of the full solar cycle from "terminator" to "terminator". These landmarks are clearer and more consistent than using sunspots to measure cycle length. For example, “the maximum number of sunspots doesn’t exactly correspond to the moment when the polar field reverses, but the polar field reversal occurs exactly one-fifth of the cycle of transition from“ terminator ”to“ terminator ”,” Limon says.
After two-fifths of the cycle, dark areas called"polar coronal holes", re-form at the poles of the Sun. Three-fifths of the cycle is the last X-flare, a class of very large and potentially dangerous solar flares. At four-fifths of the sunspots, there is a minimum, but this landmark is less constant. And then the sun passes another "terminator", after which solar activity quickly picks up again. Other phenomena, such as UV radiation, also fit perfectly with the fifth.
The team identified patterns in the data,collected daily by two ground-based observatories. The Dominion Radio Astrophysical Observatory in Penticton, Canada has been measuring solar radio flux daily since 1947, which serves as a useful indicator of solar activity. The Wilcox Solar Observatory at Stanford University has been collecting daily measurements of magnetic fields on the Sun's surface since 1975.
New Sundial Theory Changes Focus Fromsunspots to shifts in magnetic fields. "It's almost like symptoms and causes," Lemon says. While sunspots are an important symptom, the magnetic field is the primary cause driving the solar cycle.
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