Susan Macmillan
British Geological Survey
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Susan Macmillan.
Earth, Planets and Space | 2015
Erwan Thébault; Christopher C. Finlay; Ciaran Beggan; Patrick Alken; Julien Aubert; Olivier Barrois; F. Bertrand; T. N. Bondar; Axel Boness; Laura Brocco; Elisabeth Canet; Aude Chambodut; Arnaud Chulliat; Pierdavide Coïsson; François Civet; Aimin Du; Alexandre Fournier; Isabelle Fratter; N. Gillet; Brian Hamilton; Mohamed Hamoudi; Gauthier Hulot; Thomas Jager; Monika Korte; Weijia Kuang; Xavier Lalanne; Benoit Langlais; Jean-Michel Leger; Vincent Lesur; F. J. Lowes
The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic field.
Earth, Planets and Space | 2000
Mioara Mandea; Susan Macmillan
The eighth generation of the International Geomagnetic Reference Field (IGRF) was adopted in 1999 by the International Association of Geomagnetism and Aeronomy (IAGA) Division V, Working Group 8. This differs from the previous generation by the addition of the IGRF 2000 which comprises a main-field model for the epoch 2000.0 and a predictive secular-variation model for 2000.0–2005.0. This paper lists the IGRF coefficients and includes contour maps computed using IGRF 2000.
Earth, Planets and Space | 2005
Susan Macmillan; Stefan Maus
The International Geomagnetic Reference Field (IGRF) 10th Generation was adopted in 2004 by the International Association of Geomagnetism and Aeronomy (IAGA) Working Group V-MOD. It is the latest version of a standard mathematical description of the Earth’s main magnetic field and is used widely in studies of the Earth’s deep interior, its crust and its ionosphere and magnetosphere. This generation differs from the previous generation with the replacement of the secular-variation model for 2000.0–2005.0 with a main-field model at 2005.0 and a secular-variation model for 2005.0–2010.0. The IGRF is the product of a huge collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and from observatories and surveys around the world. This paper lists the new coefficients and includes contour maps and pole positions.
Geophysical Research Letters | 2000
Nils Olsen; Richard Holme; G. Hulot; Terence J. Sabaka; Torsten Neubert; L. Tøffner‐Clausen; Fritz Primdahl; John Leif Jørgensen; Jean-Michel Leger; D. Barraclough; Jeremy Bloxham; J. C. Cain; Catherine Constable; V. Golovkov; Andrew Jackson; P. Kotzé; B. Langlais; Susan Macmillan; M. Mandea; Jose M. G. Merayo; L. Newitt; Michael E. Purucker; T. Risbo; M. Stampe; Alan Thomson; Coerte V. Voorhies
Magnetic measurements taken by the Orsted satellite during geomagnetic quiet conditions around Jan-uary 1, 2000 have been used to derive a spherical harmonic model of the Earths magnetic field for epoch 2000.0. The maximum degree and order of the model is 19 for internal, and 2 for external, source fields; however, coefficients above degree 14 may not be robust. Such a detailed model exists for only one previous epoch, 1980. Achieved rms misfit is < 2 nT for the scalar intensity and < 3 nT for one of the vector components perpendicular to the magnetic field. For scientific purposes related to the Orsted mission, this model supercedes IGRF 2000.
Earth, Planets and Space | 2013
Nils Olsen; Eigil Friis-Christensen; Rune Floberghagen; Patrick Alken; Ciaran Beggan; Arnaud Chulliat; Eelco Doornbos; Joao Encarnacao; Brian Hamilton; Gauthier Hulot; Jose van den IJssel; Alexey Kuvshinov; Vincent Lesur; H. Lühr; Susan Macmillan; Stefan Maus; Max Noja; Poul Erik Holmdahl Olsen; Jaeheung Park; Gernot Plank; Christoph Püthe; Jan Rauberg; Patricia Ritter; Martin Rother; Terence J. Sabaka; Reyko Schachtschneider; Olivier Sirol; Claudia Stolle; E. Thébault; Alan Thomson
Swarm, a three-satellite constellation to study the dynamics of the Earth’s magnetic field and its interactions with the Earth system, is expected to be launched in late 2013. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, in order to gain new insights into the Earth system by improving our understanding of the Earth’s interior and environment. In order to derive advanced models of the geomagnetic field (and other higher-level data products) it is necessary to take explicit advantage of the constellation aspect of Swarm. The Swarm SCARF (SatelliteConstellationApplication andResearchFacility) has been established with the goal of deriving Level-2 products by combination of data from the three satellites, and of the various instruments. The present paper describes the Swarm input data products (Level-1b and auxiliary data) used by SCARF, the various processing chains of SCARF, and the Level-2 output data products determined by SCARF.
Earth, Planets and Space | 2013
Susan Macmillan; Nils Olsen
The ESA Swarm mission to identify and measure very accurately the different magnetic signals that arise in the Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere, which together form the magnetic field around the Earth, has increased interest in magnetic data collected on the surface of the Earth at observatories. The scientific use of Swarm data and Swarm-derived products is greatly enhanced by combination with observatory data and indices. As part of the Swarm Level-2 data activities plans are in place to distribute such ground-based data along with the Swarm data as auxiliary data products. We describe here the preparation of the data set of ground observatory hourly mean values, including procedures to check and select observatory data spanning the modern magnetic survey satellite era. We discuss other possible combined uses of satellite and observatory data, in particular those that may use higher cadence 1-second and 1-minute data from observatories.
Earth, Planets and Space | 2005
Vincent Lesur; Susan Macmillan; Alan Thomson
We describe the candidate models submitted by the British Geological Survey for the 12th generation International Geomagnetic Reference Field. These models are extracted from a spherical harmonic ‘parent model’ derived from vector and scalar magnetic field data from satellite and observatory sources. These data cover the period 2009.0 to 2014.7 and include measurements from the recently launched European Space Agency (ESA) Swarm satellite constellation. The parent model’s internal field time dependence for degrees 1 to 13 is represented by order 6 B-splines with knots at yearly intervals. The parent model’s degree 1 external field time dependence is described by periodic functions for the annual and semi-annual signals and by dependence on the 20-min Vector Magnetic Disturbance index. Signals induced by these external fields are also parameterized. Satellite data are weighted by spatial density and by two different noise estimators: (a) by standard deviation along segments of the satellite track and (b) a larger-scale noise estimator defined in terms of a measure of vector activity at the geographically closest magnetic observatories to the sample point. Forecasting of the magnetic field secular variation beyond the span of data is by advection of the main field using core surface flows.
Earth, Planets and Space | 2007
Susan Macmillan; Anna Droujinina
Long-term changes in the magnetic environment of the Earth are of interest to those studying space weather and climate change, particularly in the upper atmosphere. In this paper we examine long-term changes in daily variation as derived from hourly mean values from 14 geomagnetic observatories around the world. Their time series date back to the beginning of the 20th century. We find that there are similar features in all the records, with peaks in the amplitudes of the daily variation occurring in the 1950s and 1980s, and a small upward trend of 1.3 nT/century corresponding to an increase of over 10%. The extrema coincide with those seen in solar irradiance proxy data, in particular the F10.7 flux density dataset which starts in 1947.
Eos, Transactions American Geophysical Union | 2005
Stefan Maus; Susan Macmillan
The International Association of Geomagnetism and Aeronomy (IAGA) released the 10th Generation International Geomagnetic Reference Field (IGRF) on 12 December 2004. This is the latest version of a standard mathematical description of the Earths main magnetic field, and is used widely in studies of the Earths deep interior, crust, ionosphere, and magnetosphere. The coefficients were finalized by a task force of IAGA, Division V, Working Group V-MOD: Geomagnetic Field Modeling. The IGRF is the product of a large collaborative effort between magnetic field modelers and the institutes around the world involved in collecting and disseminating magnetic field data from satellites and observatories.
Earth, Planets and Space | 2000
Susan Macmillan; J. M. Quinn
The method of derivation of the joint UK/US spherical harmonic geomagnetic main-field and secular-variation models is presented. Early versions of these models, with the main field truncated at degree 10, are the UK/US candidates for the IGRF 2000 model. The main-field model describes the Earth’s magnetic field at the 2000.0 epoch, while the secular-variation model predicts the evolution of this field between 2000.0 and 2005.0. A revised 1995.0 main-field model was also generated. Regional models for the continental US, Alaska and Hawaii were also produced as a by-product of the UK/US global modelling effort.