(Phys.org) —Something unexpected is happening on the Sun. 2013 was supposed to be the year of "solar maximum," the peak of the 11-year sunspot cycle. Yet 2013 has arrived and solar activity is relatively low. Sunspot numbers are well below their values from 2011, and strong solar flares have been infrequent.
The image above shows the Earth-facing surface of the Sun on February 28, 2013, as observed by the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory. HMI observes the solar disk at 6173 Ångstroms, a wavelength designed to study surface oscillations and the magnetic field.
HMI observed just a few small sunspots on an otherwise clean face, which is usually riddled with many spots during peak solar activity.
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