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

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Chris TurbittObservatories ManagerGeomagnetism Team

British Geological Survey

BGS Observatory Network

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© NERC All rights reservedGlatzmaier & Roberts, 1995Jackson et al. (2000)

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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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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)