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© NERC All rights reserved
Chris TurbittObservatories ManagerGeomagnetism Team
British Geological Survey
BGS Observatory Network
© NERC All rights reserved
© NERC All rights reservedGlatzmaier & Roberts, 1995Jackson et al. (2000)
© NERC All rights reserved
Total Field (nT)
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Ascension
Port Stanley
South Georgia
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Variation at 2015.0 from BGS ModelAnnual Rate of Change Variation
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© NERC All rights reserved
© NERC All rights reserved
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
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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)
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• 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 locationsand weather conditions
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Royal Navy South Atlantic Sites 1993-2015
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
Ascension, Donkey PlainAscension, Round TowerSt HelenaTristan da CunhaFalklands, Sapper HillFalklands, Navy PointS. Georgia, Susa PointDeception Is.King George Is, Potters CoveJames Ross Is, CoastAdelaide Is, RotheraAstrolabe IsJanus
Site occupied - full measurement Site occupied - part measurement
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BGS Reference Documents
Guide to South Atlantic Sites
Magnetic Observation Instructions
(full measurement / fluxgate-theodolite with
single proton / proton only)