1. © NERC All rights reserved Chris Turbitt Observatories Manager Geomagnetism Team British Geological Survey BGS Observatory Network

2. © NERC All rights reserved

3. Glatzmaier & Roberts, 1995 Jackson et al. (2000)

4. © NERC All rights reserved Total Field (nT)

5. © NERC All rights reserved Ascension Port Stanley South Georgia

6. © NERC All rights reserved Variation at 2015.0 from BGS Model Annual Rate of Change Variation

7. © NERC All rights reserved

9. St. Patrick’s day storm 2015 – the largest storm this solar cycle Fast Coronal Mass Ejection launched from the Sun 2015-03-15 02:00Z SUN CME Arrived at Earth 2015-03-17 04:45Z Alaska Δ declination > 8° within ¼ hour

10. © NERC All rights reserved Magnetic Field Components Declination (Variation) is the angle between True North and the local magnetic meridian True North Magnetic North Horizontal Component (H) Vertical Component (Z) Total Field (F) Inclination is the angle between the H component and the total field (F) Declination (D) Inclination (I)

11. © NERC All rights reserved Reduction of data and application to global magnetic field models Output of models: Charts of the field strength, direction and the and rate of change (secular variation) Magnetic Measurement Objectives Regular (annual) measurements of the earth’s main field strength & direction Spot values of three components field: D, I and F made at precisely the same position Often in difficult locations and weather conditions

12. © NERC All rights reserved Royal Navy South Atlantic Sites 1993-2015

13. © NERC All rights reserved BGS Reference Documents Guide to South Atlantic Sites Magnetic Observation Instructions (full measurement / fluxgate-theodolite with single proton / proton only)