Deep Minimum

Solar physicists at the American Astronomical Society are taking various approaches to explain the recent record-setting decrease in energetic activity on the Sun. The rate of activity, such as coronal mass ejections and solar flares, fluctuates within 11-year solar cycles. The evolution of cycles, indicated by sun spots, is characterized by a peak in activity known as solar maximum and a corresponding decrease in activity called solar minimum. This past cycle’s solar minimum is described as “surprisingly deep and long,” and even “the deepest on record,” but scientists have yet to explain the peculiar geomagnetic activity, weakness of solar magnetic fields, and deflection of cosmic rays.

One approach towards figuring it out looks at the meridional flow, a current that moves from the equator to the poles. Another method examines the jet stream to track acoustic oscillations of the Sun and predict the timing of cycles. Yet another predictor of cycle timing uses magnetic maps to track regional differences on the Sun’s surface. This past cycle’s high-speed meridional flow and frequency shifts make for an “interesting minimum” for helioscientists, but the data poses more questions than answers.

While the latest minimum set records for length and stark inactivity, it’s notable that previous records include only a few cycles. Heliophysical forecasting research continues to unfold over many solar cycles to reveal the patterns of energetic activity of our home star.

Image by Nasa/Goddard on Flickr courtesy of Creative Commons Licensing.