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article imageAuroras in prospect as Sun's magnetic field nears 11 year flip

By Robert Myles     Nov 11, 2013 in Science
Stanford - Physicists at California’s Stanford University are preparing to monitor a rare event that comes round only once every 11 years and whose effects will reverberate through the solar system.
The Sun is about to reverse its polarity, when its magnetic north and south "flip." Such an occurrence is now imminent, say the Stanford scientists.
What causes the Sun to shift its polarity is not clearly understood but such changes in the Sun’s magnetic field have now been monitored by Stanford’s Wilcox Solar Observatory on a daily basis since 1975. In the intervening 38 years, they observed three previous shifts in the Sun’s polarity and have become familiar with the process as it is observed on the Sun’s surface.
During a solar cycle lasting 11 years, reverse polarity builds as sunspots appear as dark blotches near the Sun’s equator. Sunspots are symptomatic of the intense magnetic activity being experienced by the Sun. A sunspot will spread out over the course of a month, and the magnetic field associated with it will gradually migrate to one of the Sun’s poles.
October 2013, as WUWT reported, saw the biggest increase in sunspot activity yet observed in the current solar cycle.
As Todd Hoeksema, a solar physicist at Stanford and director of the Wilcox Solar Observatory explained, when the polarity moves towards the pole, it erodes the existing opposite polarity. He compared the phenomenon to Earth’s ocean tides, adding, “It’s kind of like a tide coming in or going out. Each little wave brings a little more water in, and eventually you get to the full reversal.”
When the Sun’s magnetic field flips, the effects are experienced not just here on Earth but throughout the solar system and beyond. At the peak of the Sun’s magnetic field reversal, there’s usually a surge of solar flares and mass ejections of charged particles from the Sun’s surface. These exert an influence over an area of space called the heliosphere. The heliosphere stretches well beyond the orbit of Pluto into an area of space, the threshold of interstellar space, currently being traversed by NASA’s Voyager space probe.
On Earth the effects of the Sun’s changing magnetic field and bursts of charged particles interact with Earth’s own magnetic field. This gives rise to both an increased incidence and wider visible range of auroras. But such bursts of solar activity also have a downside since they can also disrupt systems relying on electronic components like power distribution grids and GPS satellites.
And the effects of the solar "flip" are by no means exclusive to Earth. Said Hoeksema. “Jupiter has storms, Saturn has auroras, and this is all driven by activity of the Sun.”
Because Stanford’s Wilcox Solar Observatory data sets span almost four decades, it holds one of the most complete records encompassing daily changes in the Sun’s magnetic field. During the current solar cycle, one of the curiosities noted by Stanford observers is that the sun's hemispheres are changing at different rates. The Sun’s northern hemispheric magnetic field flipped during summer 2013; physicists now await the imminent flip of the magnetic field in the southern hemisphere.
Another curiosity of this solar cycle was has been the relative weakness of the magnetic fields at the solar poles measured two or three years ago. These were only half what they usually are at the solar minimum indicating that the upcoming solar cycle will be weak as well, a projection which, says Hoeksma, is being borne out by current measurements
Looking ahead Hoeksma added, “What happens in the next cycle will be interesting. Technologically, it’s something we need to pay more attention to as time goes on.”
He may have a point. A weak solar cycle has coincided with a rash of electronic gadgets becoming more and more part of daily life here on Earth. Just think back 11 years to a smartphone-free existence, an iPad-less planet and a time when Wi-Fi sounded like a pretentious name one might give a pet dog.
The next solar cycle might not be so gadget-friendly.
More about Solar cycle, Solar flares, sunspots, stanford university, auroras
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