The General Lighthouse Authorities of the United Kingdom and Ireland (GLA) provide marine Aids-to-Navigation (AtoNs) for the benefit and safety of all mariners within their waters. These AtoNs include traditional lighthouses, buoys and various radionavigation systems.
It is recognised that GPS, or more generally Global Navigation Satellite Systems (GNSS), have become the primary means of obtaining Position, Navigation and Timing (PNT) information at sea. Mariners may have come to believe that GPS is infallible, yet it is known to be vulnerable to solar activity, interference and system failures.
The Sun continuously releases random bursts of energy and highly charged particles. The impact of these emissions on the Earth is known as space weather. Bursts of electromagnetic energy can result in radio blackouts; bursts of high energy particles can increase ionising radiation and affect space craft performance; and bursts of magnetised plasma can result in the degradation and potential loss of radionavigation signals on Earth.
The amount of solar activity is linked with the natural sunspot cycle, which shows the number of sunspots peak approximately every 11 years, with the next peak due in 2013. Sunspots occur almost continuously, but normally give rise to weak solar events that generally go by unnoticed. However significant storms can occur at any time and as we approach peak activity, the number of space weather events will increase.
AtoNs generally report their position using radio systems, whether through the Automatic Identification System (AIS), public networks or dedicated links; and often use GNSS to calculate their position and to obtain timing information. Mariners use GNSS for PNT information; with this information integrated into many different bridge systems. Powerful solar storms can affect GNSS performance and the reception of their signals, which may lead to different correlated events, both on and off the ship. During very extreme and very rare storms, national power systems may be switched off to protect the infrastructure which would clearly affect those services relying on mains power without backup.
This paper reports the output of a study into the potential effects of space weather on GLA AtoN service provision and presents mitigating actions, where appropriate. The outcome of this study will help the GLA to continue to provide the highest level of AtoN availability, helping to ensure the safety of all mariners.
 Thompson A. P. et al, Surface Electric Fields and Geomagnetically Induced Currents in the Scottish Power Grid During the 30th October 2003 Geomagnetic Storm, British Geological Survey.
 UK & US Collaboration on space weather monitoring, http://www.number10.gov.uk/news/uk-us-higher-education-science-and-innovation-collaboration/.
 UK Cabinet Office, National Risk register of Civil Emergencies, 2012 edition.
 UK House of Commons Defence Committee, Developing Threats: Electro- -Magnetic Pulses (EMP), Tenth report of session 2010-12.
 United States National Space Weather Program Implementation Plan, 2nd Edition, July 2000.
 US National Space Weather Program: The implementation plan, 2nd ed. Committee for Space Weather, Office of the Federal Coordinator for Meteorological Services and Supporting Research Rep.OFCM-P31-2000, available online at www.ofcm.gov/nswp-ip/pdf/nswpip.pdf.
 US Space Weather Prediction Centre, http://www.swpc.noaa.gov/aurora/globeNE.html.