The last “sunspot maximum” occurred in 2000 and was followed by a period of decreasing sunspot numbers, but scientists are now seeing evidence suggesting the number may be starting to rise again. If the normal pattern continues they should peak around 2011.

An example of what can be expected in the next few years, as solar activity starts to rise again, occurred on 13 December 2006 when a massive solar flare ejected huge amounts of energy and matter from the sun’s surface into space.

“The impact of this event on GPS users would have been variable, largely dependent on the GPS receiver in use. Solar radio bursts compromise GPS operation by directly increasing the system noise of the GPS receiver lowering the signal to noise ratio (SNR) of the signal from each satellite being tracked by the receiver. If the SNR from a given satellite drops to a level at which the receiver can no longer track, a loss of lock occurs on that satellite. Each satellite tracking loss reduces the accuracy of the navigation solution, until a navigation solution is no longer possible,” said Dr Mike Terkildsen from the IPS Radio and Space Services, which acts as the Australian Space Weather Agency.

“We observed significant signal degradation in a number of GPS receivers for the duration of the 2-hour burst and complete drop-outs in GPS satellite tracking for a five-minute period near the peak of the solar burst. Other receivers continued to track all satellites throughout the burst on a reduced signal to noise level,” he said.

The resulting high levels of magnetic-field activity (a magnetic storm) on 14 December 2006 degraded the accuracy of some GPS positions, caused disruptions to magnetic surveying operations and induced anomalous electrical currents in satellite circuits, power lines and pipelines.

“Long pipelines are affected by the variations of the Earth’s magnetic field such as those that occur during geomagnetic storms. These variations, referred to as the primary or source fields, induce a secondary magnetic field and associated electric field at the Earths surface often referred to as the geoelectric field,” said Dr Richard Marshall also from the IPS Radio and Space Services.

“This geoelectric field drives currents in long pipelines referred to as ‘telluric currents’ which depend on the pipeline’s resistivity, geometry, and orientation with respect to the geoelectric field. As a result of variations in the pipeline structure and soil conductivities, the ‘telluric currents’ give rise to pipe-to-soil potentials (PSPs) which can vary at different points along the pipeline and may contribute to corrosion,” he said.

During times of significant geomagnetic activity, cathodic protection systems designed to protect pipelines from corrosion may need to be adjusted to compensate for these telluric current-associated PSPs. Some cathodic protection units have feedback systems so that the voltage applied to the pipeline varies in relation to the amount of telluric current activity.

Dr Marshall also noted that the Australian Standard for the Cathodic protection of metals, Part 1: Pipes and cables (AS2832.1) stipulates that during surveys of structures to be evaluated for telluric stray current effects “the potential of structures that are subject to telluric current effects shall not be more positive than the protection criteria for more than 10% of the test period. When determining the extent of the potential variations, an assessment should be made of the degree of ionospheric disturbance at the time of the recording.”

“Although solar flare activity of this nature is not common during solar minimum, they are likely to increase in occurrence frequency as we approach solar maximum,” Dr Terkildsen said.

IPS Radio and Space Services continually monitor the space weather environment for geomagnetic and ionospheric disturbances. They are working with industry groups to develop services and contingency measures ahead of sunspot maximum due around 2011.