Abstract
The geomagnetic field one can measure at the Earth’s surface or on board satellites is the sum of contributions from many different sources. These sources have different physical origins and can be found both below (in the form of electrical currents and magnetized material) and above (only in the form of electrical currents) the Earth’s surface. Each source happens to produce a contribution with rather specific spatio-temporal properties. This fortunate situation is what makes the identification and investigation of the contribution of each source possible, provided appropriate observational data sets are available and analyzed in an adequate way to produce the so-called geomagnetic field models. Here we provide a general overview of the various sources that contribute to the observed geomagnetic field, and of the modern data that enable their investigation via such procedures.The Earth has a large and complicated magnetic field, a major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. What is measured at or near the surface of the Earth, however, is the superposition of the core field and of additional fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere and oceans, and by currents induced in the Earth by the time-varying external fields. The sophisticated separation of these various fields and the accurate determination of their spatial and temporal structure based on magnetic field observations is a significant challenge, which requires advanced modeling techniques (see e.g., Hulot et al. 2007). These techniques rely on a number of mathematical properties which we review in the accompanying chapter by Sabaka et al. (2010), entitled Mathematical Properties Relevant to Geomagnetic Field Modeling. But as many of those properties have been derived by relying on assumptions motivated by the nature of the various sources of the Earth’s magnetic field and of the available observations, it is important that a general overview of those sources and observations be given. This is precisely the purpose of the present chapter. It will first describe the various sources that contribute to the Earth’s magnetic field (Sect. 1) and next discuss the observations currently available to investigate them (Sect. 2). Special emphasis is given on data collected by satellites, since these are extensively used for modeling the present magnetic field. We will conclude with a few words with respect to the way the fields those sources produce can be identified and investigated, thanks to geomagnetic field modeling.
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Notes
- 1.
Actually the satellite revisits that region already after about 12 h, but this will be for a different local time. Because of external field contributions – which heavily depend on local time – it is safer to rely on data taken at similar local time conditions, which results in the above stated sampling recurrence of 24 h.
References
Alexandrescu MM, Gibert D, Le Mouël JL, Hulot G, Saracco G (1999) An estimate of average lower mantle conductivity by wavelet analysis of geomagnetic jerks. J Geophys Res 104: 17735–17745
Cain JC (2007) POGO (OGO-2, -4 and -6 spacecraft). In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg, pp 828–829
Campbell WH (1989) The regular geomagnetic field variations during quiet solar conditions. In: Jacobs JA (ed) Geomagnetism, vol 3. Academic, London, pp 385–460
Constable S (2007) Geomagnetic induction studies. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam, pp 237–276
Cowling TG (1957) Magnetohydrodynamics. Wiley Interscience, New York
Dunlop D, Özdemir Ö (2007) Magnetizations in rocks and minerals. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam, pp 277–336
Finlay CF, Dumberry M, Chulliat A, Pais A (2010) Short timescale core dynamics: theory and observations. Space Sci Rev 155:177–218. doi:10.1007/s11214-010-9691-6
Friis-Christensen E, Lühr H, Hulot G (2006) Swarm: a constellation to study the Earth’s magnetic field. Earth Planets Space 58:351–358
Friis-Christensen E, Lühr H, Hulot G, Haagmans R, Purucker M (2009) Geomagnetic research from space. EOS Trans AGU 90(25):213–215
Gubbins D, Zhang K (1993) Symmetry properties of the dynamo equations for paleomagnetism and geomagnetism. Phys Earth Planet Int 75:225–241
Hemant K, Maus S (2005) Geological modeling of the new CHAMP magnetic anomaly maps using a geographical information system technique. J Geophys Res 110:B12103. doi:10.1029/2005JB003837
Hulot G, Le Mouël JL (1994) A statistical approach to the Earth’s main magnetic field. Phys Earth Planet Int 82:167–183. doi:10.1016/0031-9201(94)90070-1
Hulot G, Sabaka TJ, Olsen N (2007) The present field. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam, pp 33–75
Hulot G, Olsen N, Thébault E, Hemant K (2009) Crustal concealing of small-scale core-field secular variation. Geophys J Int 177:361–366. doi:10.1111/j.1365-246X. 2009.04119.x
Hulot G, Finlay C, Constable C, Olsen N, Mandea M (2010) The magnetic field of planet Earth. Space Sci Rev 152:159–222. doi:10.1007/s11214-010-9644-0
Jackson A, Finlay CC (2007) Geomagnetic secular variation and its application to the core. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam
Jacobs JA (1953) The earth’s inner core. Nature 172:297–300
Jankowski J, Sucksdorff C (1996) IAGA guide for magnetic measurements and observatory practice. IAGA, Warszawa
Kivelson MG, Russell CT (1995) Introduction to space physics. Cambridge University Press, Cambridge
Kuvshinov A (2008) 3-D global induction in the oceans and solid earth: recent progress in modeling magnetic and electric fields from sources of magnetospheric, ionospheric and oceanic origin. Surv Geophys 29(2):139–186
Kuvshinov A (2012) Deep electromagnetic studies from land, sea, and space: progress status in the past 10 years. Surv Geophys 33:169–209. doi:10.1007/s10712-011-9118-2
Kuvshinov AV, Olsen N (2005) 3D modeling of the magnetic field due to ocean flow. In: Reigber C, Lühr H, Schwintzer P, Wickert J (eds) Earth observation with CHAMP, results from three years in orbit. Springer, Berlin
Kuvshinov AV, Olsen N (2006) A global model of mantle conductivity derived from 5 years of CHAMP, Ørsted, and SAC-C magnetic data. Geophys Res Lett 33:L18301. doi:10.1029/2006GL027083
Kuvshinov AV, Sabaka TJ, Olsen N (2006) 3-D electromagnetic induction studies using the Swarm constellation. Mapping conductivity anomalies in the Earth’s mantle. Earth Planets Space 58:417–427
Langel RA, Hinze WJ (1998) The magnetic field of the Earth’s lithosphere: the satellite perspective. Cambridge University Press, Cambridge
Langel RA, Estes RH, Mead GD (1982) Some new methods in geomagnetic field modeling applied to the 1960–1980 epoch. J Geomagn Geoelectron 34:327–349
Lesur V, Jackson A (2000) Exact solution for internally induced magnetization in a shell. Geophys J Int 140:453–459
Lesur V, Wardinski I, Rother M, Mandea M (2008) GRIMM: the GFZ reference internal magnetic model based on vector satellite and observatory data. Geophys J Int 173:382–394
Lesur V, Olsen N, Thomson AW (2011) Geomagnetic core field models in the satellite era. In: Mandea M, Korte M (eds) Geomagnetic observations and models. IAGA special Sopron book series, chap 11, vol 5. Springer, Heidelberg, pp 277–294. doi:10.1007/978-90-481-9858-0_11
Lowes FJ (1966) Mean-square values on sphere of spherical harmonic vector fields. J Geophys Res 71:2179
Lühr H, Maus S (2006) Direct observation of the F region dynamo currents and the spatial structure of the EEJ by CHAMP. Geophys Res Lett 33:L24102. doi:10.1029/2006GL028374
Lühr H, Maus S, Rother M (2002) First in situ observation of night-time F region currents with the CHAMP satellite. Geophys Res Lett 29(10). doi:10.1029/2001GL013845
Maus S (2007a) CHAMP magnetic mission. In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg, pp 59–60
Maus S (2007b) Electromagnetic ocean effects. In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg
Maus S, Haak V (2003) Magnetic field annihilators: invisible magnetization at the magnetic equator. Geophys J Int 155:509–513
Maus S, Lühr H (2005) Signature of the quiet-time magnetospheric magnetic field and its electromagnetic induction in the rotating Earth. Geophys J Int 162:755–763
Maus S, Lühr H (2006) A gravity-driven electric current in the Earth’s ionosphere identified in CHAMP satellite magnetic measurements. Geophys Res Lett 33:L02812. doi:10.1029/2005GL024436
Maus S, Yin F, Lühr H, Manoj C, Rother M, Rauberg J, Michaelis I, Stolle C, Müller R (2008) Resolution of direction of oceanic magnetic lineations by the sixth-generation lithospheric magnetic field model from CHAMP satellite magnetic measurements. Geochem Geophys Geosyst 9(7):Q07021. doi:10.1029/2008GC001949
Merrill R, McFadden P, McElhinny M (1998) The magnetic field of the earth: paleomagnetism, the core, and the deep mantle. Academic, San Diego
Newitt LR, Barton CE, Bitterly J (1996) Guide for magnetic repeat station surveys. International Association of Geomagnetism and Aeronomy, Boulder
Nimmo F (2007) Energetics of the core. In: Treatise on geophysics, G. Schubert (ed), vol 8. Elsevier, Amsterdam, pp 31–65
Olsen N (1997a) Ionospheric F region currents at middle and low latitudes estimated from Magsat data. J Geophys Res 102(A3):4563–4576
Olsen N (1997b) Geomagnetic tides and related phenomena. In: Wilhelm H, Zürn W, Wenzel H-G (eds) Tidal phenomena. Lecture notes in earth sciences, vol 66. Springer, Berlin/New York
Olsen N (2007a) Ørsted. In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg, pp 743–745
Olsen N (2007b) Natural sources for electromagnetic induction studies. In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg
Olsen N, Lühr H, Sabaka TJ, Mandea M, Rother M, Tøffner-Clausen L, Choi S (2006) CHAOS – a model of Earth’s magnetic field derived from CHAMP, Ørsted, and SAC-C magnetic satellite data. Geophys J Int 166:67–75. doi:10.1111/j.1365-246X. 2006.02959.x
Olsen N, Mandea M, Sabaka TJ, Tøffner-Clausen L (2009) CHAOS-2 – a geomagnetic field model derived from one decade of continuous satellite data. Geophys J Int 179(3):1477–1487. doi:10.1111/j.1365-246X.2009.04386.x
Olsen N, Hulot G, Sabaka TJ (2010a) Measuring the Earth’s magnetic field from space: concepts of past, present and future missions. Space Sci Rev 155:65–93. doi:10.1007/s11214-010-9676-5
Olsen N, Mandea M, Sabaka TJ, Tøffner-Clausen L (2010b) The CHAOS-3 geomagnetic field model and candidates for the 11th generation of IGRF. Earth Planets Space 62:719–727
Parkinson WD, Hutton VRS (1989) The electrical conductivity of the earth. In: Jacobs JA (ed) Geomagnetism, vol 3. Academic, London, pp 261–321
Purucker ME (2007) Magsat. In: Gubbins D, Herrero-Bervera E (eds) Encyclopedia of geomagnetism and paleomagnetism. Springer, Heidelberg, pp 673–674
Purucker M, Whaler K (2007) Crustal magnetism. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam, pp 195–235
Purucker M, Langlais B, Olsen N, Hulot G, Mandea M (2002) The southern edge of cratonic North America: evidence from new satellite magnetometer observations. Geophys Res Lett 29(15):8000. doi:10.1029/2001GL013645
Rastogi RG (1989) The equatorial electrojet: magnetic and ionospheric effects. In: Jacobs JA (ed) Geomagnetism, vol 3. Academic, London, pp 461–525
Richmond AD (1989) Modeling the ionospheric wind dynamo: a review. In: Campbell WH (ed) Quiet daily geomagnetic fields. Birkhäuser Verlag, Basel
Richmond AD (2002) Modeling the geomagnetic perturbations produced by ionospheric currents, above and below the ionosphere. J Geodynamics 33:143–156
Roberts PH (2007) Theory of the geodynamo. In: Treatise on geophysics, vol 8. Elsevier, Amsterdam, pp 67–106
Runcorn SK (1975) On the interpretation of lunar magnetism. Phys Earth Planet Int 10:327–335
Sabaka TJ, Olsen N (2006) Enhancing comprehensive inversions using the Swarm constellation. Earth Planets Space 58:371–395. http://www.terrapub.co.jp/journals/EPS/pdf/2006/5804/58040371.pdf
Sabaka TJ, Olsen N (2004) Purucker ME Extending comprehensive models of the Earth’s magnetic field with Ørsted and CHAMP data. Geophys J Int 159:521–547. doi:10.1111/j.1365-246X.2004.{02421}.x
Sabaka TJ, Olsen N, Langel RA (2002) A comprehensive model of the quiet-time near-Earth magnetic field: phase 3. Geophys J Int 151:32–68
Sabaka TJ, Hulot G, Olsen N (2010) Mathematical properties relevant to geomagnetic field modeling. In: Freeden W, Nashed Z, Sonar T (eds) Handbook of geomathematics, chap 17. Springer, Heidelberg, pp 504–538. doi:10.1007/978-3-642-01546-5_17
Schmucker U (1985) Magnetic and electric fields due to electromagnetic induction by external sources. In: Landolt-Börnstein, new-series, 5/2b, W. Martienssen (ed). Springer, Berlin/Heidelberg, pp 100–125
Schott J-J, Thebault E (2011) Modeling the Earth’s magnetic field from global to regional scales. In: Mandea M, Korte M (eds) Geomagnetic observations and models. IAGA special Sopron book series, chap 9, vol 5. Springer, Heidelberg. doi:10.1007/978-90-481-9858-0_2
Thebault E, Hemant K, Hulot G, Olsen N (2009) On the geographical distribution of induced time-varying crustal magnetic fields. Geophys Res Lett 36:L01307. doi:10.1029/2008GL036416
Thébault E, Purucker M, Whaler KA, Langlais B, Sabaka TJ (2010) The magnetic field of the Earth’s lithosphere. Space Sci Rev 155:95–127. doi:10.1007/ s11214-010-9667-6
Thomson AWP, Lesur V (2007) An improved geomagnetic data selection algorithm for global geomagnetic field modeling. Geophys J Int 169(3):951–963
Turner GM, Rasson JL, Reeves CV (2007) Observation and measurement techniques. In: Kono M (ed) Treatise on geophysics, vol 5. Elsevier, Amsterdam
Tyler RH, Maus S, Lühr H (2003) Satellite observations of magnetic fields due to ocean tidal flow. Science 299:239–241
Voorhies CV, Sabaka TJ, Purucker M (2002) On magnetic spectra of Earth and Mars. J Geophys Res 107(E6):5034
Wicht J, Harder H, Stellmach S (2010) Numerical dynamo simulations – from basic concepts to realistic models. In: Freeden W, Nashed Z, Sonar T (eds) Handbook of geomathematics. Springer, Heidelberg
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Olsen, N., Hulot, G., Sabaka, T.J. (2015). Sources of the Geomagnetic Field and the Modern Data That Enable Their Investigation. In: Freeden, W., Nashed, M., Sonar, T. (eds) Handbook of Geomathematics. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-54551-1_5
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