Here at Science World, one of our favorite topics is the sun. We’ve been able to provide you with a number of informational pieces regarding events and phenomena such as the ebb and flow of the sun’s activity throughout its roughly 11 year solar cycle.
As the sun goes through this process – from when it’s least active (solar minimum) to its most active (solar maximum) and back again – it undergoes what scientists describe as a “complete makeover” when its magnetic field reverses or flips its polarity. The sun’s magnetic north becomes its south and vice versa, causing effects that can ripple throughout our solar system.
Scientists say that our sun, which is nearing the peak of its current solar cycle, is about to flip its magnetic poles. The current solar cycle that began in 2008 or 2009 is the 24th since scientists started tracking them back in 1755. Compared to previous solar cycles, researchers have said that the current cycle appears to be weaker than any other before it, perhaps the weakest in 100 years.
While not much is known about the actual mechanics behind this polarity flip, solar scientists at Stanford University’s Wilcox Solar Observatory are keeping an eye on the sun’s magnetic field, monitoring and measuring it every day, as they have done since 1975.
The daily monitoring efforts allow these researchers to observe and identify the magnetic polarity reversal as it actually takes place on the sun’s surface. This upcoming shift in the Sun’s poles will be the fourth the observatory has watched.
While we laypeople tend to label the sun’s magnetic poles as north and south, Todd Hoeksema, a solar physicist and Director of the Wilcox Solar Observatory, suggests that we think of the poles as positive and negative. “It’s best not to think of it like a big bar magnet. That works OK for Earth but not the Sun. Think of the Sun as having a large number of smaller magnetic fields scattered over the surface,” he said.
Of course, hearing that the sun is about undergo a significant event like a pole reversal can alarm some people who may wonder if they might be in danger. But, according to Hoeksema we have nothing to worry about.
“When it happened about eleven or twelve years ago, you probably didn’t even notice,” he said.
Hoeksema explains that the pole reversal process takes place over time throughout the solar cycle where sunspots come up at the Sun’s mid-latitudes (equator) and spread out toward its poles. Gradually, as the magnetic flux (a measurement of the quantity of magnetism) that comes up with the sunspots moves pole-ward it erodes the existing polar fields and replaces them with magnetic fields that have the opposite polarity.
“What we’re seeing recently is more activity in the (sun’s) southern hemisphere and that’s the pole that’s just about to switch or is switching right now,” said Hoeksema.
He also pointed out that the sun’s northern pole switched about a year ago in the summer of 2012.
The sun’s two hemispheres (north and south) aren’t in perfect synchronization with each other and the number of sunspots that emerge in each of the hemispheres can be different.
Because of this, according to Hoeksema, the sun’s ‘new’ polarity that moves poleward is generally different in the north and south in both timing and strength which causes one geographic pole to change its magnetic field direction before the other.
Since it is at or near its peak of activity, the sun is has been pumping out a lot of energy particles throughout the solar system via the solar wind. Because of this outpouring of sun particles, according to Hoeksema, we’re actually being shielded from the high energy particles that come at us from other parts of the galaxy.
Along with their ground-based Wilcox Solar Observatory at Stanford, Hoeksema and his fellow scientists also use some sophisticated observational tools in space, too. One is as an instrument aboard NASA’s Solar Dynamic Observatory (SDO) called the ‘Helioseismic and Magnetic Imager’ (HMI) which allows the team to measure the sun’s magnetic field every 45 seconds.
These measurements help scientists zero in on where and what kind of solar activity is taking place on the Sun, something that Hoeksema and his colleagues hope will help scientists better predict potentially dangerous space weather.
Dr. Todd Hoeksema joins us this weekend on the radio edition of “Science World.” To listen to our conversation either tune into the show (see right column for scheduled times) or check out the interview below.
Also check out the video below.
Solar physicist Todd Hoekserma explains sun’s magnetic reversal (Stanford University)