Stanford Physicists Monitoring Huge Solar Event
Every 11 years, the sun undergoes a complete makeover when the polarity of its magnetic field – its magnetic north and south – flips. The effects of this large-scale event ripple throughout the solar system.
Although the exact internal mechanism that drives the shift is not entirely understood, researchers at Stanford’s Wilcox Solar Observatory have monitored the sun’s magnetic field on a daily basis since 1975 and can identify the process as it occurs on the sun’s surface. This will be the fourth shift the observatory has monitored.
New polarity builds up throughout the 11-year solar cycle as sunspots – areas of intense magnetic activity – appear as dark blotches near the equator of the sun’s surface. Over the course of a month, a sunspot spreads out, and gradually that magnetic field migrates from the equator to one of the sun’s poles.
As the polarity moves toward the pole, it erodes the existing, opposite polarity, said Todd Hoeksema, a solar physicist at Stanford since 1978 and director of the Wilcox Solar Observatory. The magnetic field gradually reduces toward zero, and then rebounds with the opposite polarity.