The flipping polarity

Adventures on Earth for August 18, 2010 edition
The latest issue of Earth Magazine examines the issue of the Earth’s magnetic field reversing. The magnetic field has been weakening, a possible indicator that a change is coming.
The questions for which we have no finite answer are when it will occur and what effects it will have.
The Earth’s magnetic field is caused by differential rotation of the solid iron inner core and the molten iron outer core.
There are four zones in our home planet, the solid iron inner core, the molten iron outer core, the viscous rock mantle, and the crustal surface.
The differential rotation of the two inner iron cores acts like a dynamo, putting out a magnetic field that envelops the planet.
The interaction of solar wind with the magnetic field is responsible for the aurorae that dance over polar skies.
Over time the polarity of the magnetic field has changed. The periods between changes vary, so there is no certain time measure.
The polarity flips were revealed when scientists began exploring the issue of plate tectonics, the movement of solid continents on a bed of viscous rock of the mantle.
On either side of the Mid-Atlantic Ridge, where new seabed oozes out, the polarity flips show up as bands.
When molten rock comes to the surface (or to the seafloor), the polarity in effect at that time locks the magnetism of the rock in place. To sort out when flips have occurred, scientists measure the alternating bands and date the rock.
The last reversal took place some 780,000 years ago, a time before humans arrived on the scene. So we don’t know exactly what takes place during the reversal process.
What we do know is that the process can play out over thousands of years in some cases, or in much shorter periods.
In the past, reversals have occurred in relatively rapid bursts, alternating with long periods of quiescence when nothing happens. The current period is apparently one of those long periods of quiescence.
Still, the polarity varies within that long period. We know that magnetic north moves across northern Canada. The movement of the pole requires those navigating by compass to adjust their compasses to magnetic north accordingly. The difference between magnetic north and true north is known as declination.
The magnetic field protects the planet from solar wind. As the magnetic field weakens preceding a polarity flip, there is concern that the loss or weakening of the magnetic will allow solar wind to reach the surface of the planet.
In the past, however, we do not see negative effects on life because of polarity flips. But we live in a highly technical world that can be affected by solar wind. Solar flares can disrupt radio communications, satellites, and shut down power grids.
What will happen and when it will happen remain unknown, but the reversal will happen. Until then, there is time for engineers to study ways to protect against solar wind effects on our technology.