House of Lords Arctic Committee – supplementary evidence on “sferics” and space weather impacts on communications.
During the evidence session of 28 October 2014, Lord Hunt of Chesterton asked about the use of Met Office lightning detection data (“sferics”) to provide information on the changing Arctic environment. The Met Office offered to supply further detail.
Lord Addington was interested in how electronic communications were impacted by the Arctic environment. Space weather can result in geomagnetic variations, aurora, and can affect a number of technologies, including satellite communications and positioning. Space weather predominantly affects the polar regions (the Earth's northern magnetic pole is located in the Arctic Ocean near the Canadian Arctic Archipelago) and the extent of geomagnetic activity, indicated by the aurora oval, extends to lower latitudes proportionate to the magnitude of the geomagnetic storm.
We have therefore also included a short note on the impacts of space weather and the Met Office’s space weather operations centre.
Arrival Time Difference (ATD) thunderstorm detection system
Since the mid-1980s the Met Office has operated a system for remote detection of lightning, by detecting low frequency radio waves that are triggered by lightning pulses and travel long distances (“sferics”).
In recent years the system coverage has included most of the globe, although detection efficiency over the Arctic is not as good as in some other regions such as Europe. The data are made available in near-real time to national meteorological services around the world. In the past they have also been made available to the wider research community, although we are not aware of the level of uptake.
The observing system is primarily designed to aid immediate detection and short term forecasting, and has evolved over the years as detection efficiency has improved and more detecting stations added. Detecting long term trends using these data, particularly over the Arctic, would therefore be problematic, and we are not aware of any such studies. Geostationary satellite-based systems due for implementation over the next decade or so offer the prospect of improved lightning detection globally.
Space weather impacts on satellites and electronic communications
For most of the time the Earth's magnetosphere shields satellites from the high energy radiation in space. During significant space weather events this shielding breaks down and geostationary satellites can become exposed and prone to damage. Forty seven satellites suffered temporary outages during the geomagnetic storm in Oct 2003 and two were damaged in 2012. Given the range of spacecraft in operation today the Royal Academy of Engineering estimated 10% of the satellite fleet might suffer from a temporary outage during an extreme event.
During space weather radiation storms, the high energy particles flow towards polar regions along magnetic field lines. These produce a ‘Polar Cap Absorption’ (PCA) event producing a HF communications blackout over the polar regions which typically lasts a few days. As satellite communications don’t work at such high latitudes this result in a communication blackout over the poles resulting in airlines (typically those flying from the US to Asia) having to avoid the polar regions for safety purposes.
During a severe space weather event, the increase in the radiation environment is more pronounced near the polar regions, which also increases the risk of Single Event Upsets to aircraft avionics.
Global Navigation Satellite Systems (GNSS) often known as Global Positioning Satellites (GPS) would also be impacted making such systems inoperable for a number of days. This will cause operational impacts to industries such as aviation and shipping but could also impact those which rely on GNSS for critical timing information. An extreme geomagnetic storm will also result in an expansion of the Earth's atmosphere which disrupts the orbit of satellites in a low Earth orbit degrading predictions of their position. It can take several days to reacquire positioning data and regain communication with the satellite.
Radio blackouts and loss of long distance communication
Much or our long distance communications relies on the state of a layer in the atmosphere called the ionosphere. HF communications are bounced off the ionosphere to travel beyond line of sight and spacecraft operators communicate with their satellites at VHF, UFH and higher frequencies, which pass through the ionosphere.
During solar flares the intense burst of radiation interferes with the ionosphere, absorbing HF communications signals and causing radio blackouts on the sun-lit side of the Earth. During geomagnetic and solar radiation storms the ionosphere is modified, making it difficult for VHF etc to pass through so communications signals may be degraded in or near the polar regions. As a result mobile satellite communications are of very poor quality or may also be completely unavailable. This impact is at its strongest around dusk and dawn.
Met Office Space Weather Operations Centre
The Government funds the Met Office Space Weather Operations Centre (MOSWOC) which provides operational 24/7 forecasts, alerts and warnings of the impacts of space weather to help protect the UK from the serious threats posed by space weather events.
Through our work with other partners in the UK, the Met Office will help to ensure that efforts are coordinated as part of an international programme with the US National Oceanic and Atmospheric Administration (NOAA) National Weather Service Space Weather Prediction Centre (SWPC).
The Met Office is also a member of International Space Environment Services (ISES) - international body for space weather - and is a designated Regional Warning Centre.
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