South Atlantic Anomaly and South Georgia Magnetic Observatory
Why is BGS re-establishing a magnetic observatory on South Georgia?
The South Georgia observatory will plug a significant gap in the global network of magnetic observatories. In particular South Georgia observatory will allow better monitoring of the South Atlantic Anomaly and of changes occurring deep within the Earth. By establishing the new observatory, BGS will re-start continuous magnetic observations in South Georgia, last carried out in 1982.
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What is the South Atlantic Anomaly?
The Earth’s magnetic field, generated deep within the planet, is a shield against particle radiation from space. In the South Atlantic this shield is much weaker than elsewhere across the globe and radiation from space therefore penetrates deeper into the atmosphere. This region is known as the South Atlantic Anomaly (SAA) and the radiation in the SAA is a known hazard to satellites, spacecraft and high-altitude aircraft.
Monitoring changes in magnetic field
The radiation input into the atmosphere depends on the Sun’s magnetic and radiation activity and the geometry (or ‘shape’) of the Earth’s magnetic field. So, understanding the space environment, particularly during magnetic storms, is important. Equally important is understanding any changes over time in the magnetic field observed across the surface of the Earth — see also Long-term monitoring of the Earth’s magnetic field.
A magnetic reversal in progress?
The South Atlantic Anomaly (SAA) is known to be growing in extent and spreading westwards from South Africa, as the Earth’s internal magnetic field rapidly weakens in this region. This may be early evidence of a forthcoming reversal in the direction of the Earth’s internal magnetic field. We do not know in detail precisely what occurs during such reversals, including the changes observed in the magnetic field and the time a reversal takes to complete. However these factors are important in knowing where the radiation risk may be increased and how the atmosphere might respond.
Earth’s magnetic field has had many highs, lows and reversals in its past. The last reversal was around 800,000 years ago. So the Earth is known to be able to re-generate its field and has done so during human pre-history. Understanding the development of the SAA may therefore be significant in understanding the reversal process and its impact on life and the natural environment.
New South Georgia Magnetic Observatory
By establishing a magnetic observatory on South Georgia BGS geomagnetists will specifically help to develop our understanding of the SAA by:
Joined up monitoring
Directly observing changes in the SAA in a region (mid Atlantic Ocean) poorly covered by permanent magnetic observatories. In the middle of the ocean only Ascension Island, Tristan da Cunha and St Helena observatories can provide monitoring of the magnetic field and its changes. We need to better relate observations of the SAA made separately on the land masses of Africa and South America. South Georgia observatory will therefore be a key addition to this small network of observatories.
Providing new data to construct better mathematical models of the magnetic field. Such models can be used to infer how the flow of liquid iron in the outer core of the Earth is changing. This fluid flow sustains our magnetic field and forecasting how it changes in time will help improve predictions of future change in the SAA.
Understanding the complete ‘Earth System’
Promoting collaboration between space scientists, concerned with Earth’s space environment, and geoscientists, concerned with Earth’s other environments. There are major communities of these researchers both in the UK and internationally and the expertise of both space- and geo-scientists are needed to fully understand the complete ‘Earth system’. Measuring, monitoring and modelling the Earth’s magnetic field is a key aspect of this understanding and that is BGS’ contribution to this endeavour.