Sunspots That Won't Go Away
The Sun's surface constantly generates magnetic structures that emerge, evolve, and decay over days, weeks, and months. Among these structures are active regions — patches of intense magnetic field that can produce solar flares and coronal mass ejections, the space weather events that disrupt satellites, power grids, and communications systems on Earth.
Most active regions last for a few days or weeks before their magnetic fields weaken and disperse. But some persist for more than a month, surviving multiple rotations of the Sun as it completes its roughly 27-day rotation. These long-lived active regions have always been of interest to solar physicists, but systematic data on just how unusual their behavior is has been lacking — until now.
A new study, built on observations from thousands of citizen scientists through NASA's Solar Active Region Spotter project, has produced that data, and the results are striking.
The Citizen Science Approach
The Solar Active Region Spotter project asked volunteers to examine pairs of images from NASA's Solar Dynamics Observatory and answer questions: Does this pair show the same active region? How have its characteristics changed? What is its structure?
Human pattern recognition is genuinely superior to algorithmic approaches for certain tasks involving complex, variable visual data. By aggregating observations from thousands of volunteers, the project was able to build a large, reliable dataset about how active regions evolve over time — a dataset that would have been expensive and time-consuming to build through purely automated means.
The Key Finding
Project leads Emily Mason and Kara Kniezewski found a significant statistical pattern: long-lived active regions — those persisting for at least a month — produce disproportionately more solar flares than shorter-lived regions of similar size.
Most significantly, they found that long-lived active regions are three to six times more likely than other regions to be the source of X-class solar flares — the most intense category, capable of disrupting radio communications, damaging satellites, and affecting power grid infrastructure on Earth. This disproportion is large enough to be practically important: knowing that a particular active region has persisted for more than a month should significantly raise alert levels for major flare activity.
Why Long-Lived Regions Are More Explosive
The most likely explanation involves the roots of the magnetic field: active regions that persist for weeks or months are presumably anchored more deeply in the solar interior, where the magnetic field is stronger. This deeper anchoring allows the active region to be continuously replenished with magnetic flux from below, maintaining its intensity even as surface-level processes work to weaken it. Understanding these structures better could provide insight into processes deep within the Sun that drive the solar cycle and determine the overall level of solar activity, with direct benefits for space weather forecasting.
This article is based on reporting by science.nasa.gov. Read the original article.
