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Long-term trends in geomagnetic daily variation


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.


  • Chapman, S. and J. Bartels, Geomagnetism, Vol. I, Oxford University Press, 1940.

  • Chulliat, A., E. Blanter, J.-L. Le Mouël, and M. Shnirman, On the seasonal asymmetry of the diurnal and semidiurnal geomagnetic variations, J. Geophys. Res., 110, A05301, doi: 10.1029/2004JA010551, 2005.

    Google Scholar 

  • Clilverd, M. A., T. D. G. Clark, E. Clarke, and H. Rishbeth, Increased magnetic storm activity from 1868 to 1995, J. Atmos. Solar-Terr. Phys., 60(10), 1047–1056, 1998.

    Article  Google Scholar 

  • Clilverd, M. A., E. Clarke, T. Ulrich, J. Linthe, and H. Rishbeth, Reconstructing the long-term aa index, J. Geophys. Res., 110, A07205, doi:10.1029/2004JA010762, 2005.

    Google Scholar 

  • Gustafsson, G., N. E. Papitashvili, and V. O. Papitashvili, A revised corrected geomagnetic coordinate system for Epochs 1985 and 1990, J. Atmos. Terr. Phys., 54, 1609–1631, 1992.

    Article  Google Scholar 

  • International Association of Geomagnetism and Aeronomy (IAGA), Division V, Working Group VMOD: Geomagnetic Field Modeling, The 10th-Generation International Geomagnetic Reference Field, Geophys. J. Int., 161(3), 561–565, 2005.

    Article  Google Scholar 

  • Jackson, A., A. R. T. Jonkers, and M. R. Walker, Four centuries of geomagnetic secular variation from historical records, Phil. Trans. R. Soc. Lond., A, 358, 957–990, 2000.

    Article  Google Scholar 

  • Laštovička, J. R., A. Akmaev, G. Beig, J. Bremer, and J. T. Emmert, Global change in the upper atmosphere, Science, 314, 1253–1254, 2006.

    Article  Google Scholar 

  • Le Mouël, J.-L., V. Kossobokov, and V. Courtillot, On long-term variations of simple geomagnetic indices and slow changes in magnetospheric currents: The emergence of anthropogenic global warming after 1990?, Earth Planet. Sci. Lett., 232, 273–286, 2005.

    Article  Google Scholar 

  • Lockwood, M., R. Stamper, and M. N. Wild, A doubling of the Sun’s coronal magnetic field during the past 100 years, Nature, 399, 437–439, 1999.

    Article  Google Scholar 

  • Mandea, M., E. Bellanger, and J.-L. Le Mouël, A geomagnetic jerk for the end of the 20th century?, Earth Planet. Sci. Lett., 183, 369–373, 2000.

    Article  Google Scholar 

  • Olsen, N., The solar cycle variability of lunar and solar daily geomagnetic variations, Ann. Geophys., 11, 254–262, 1993.

    Google Scholar 

  • Stamper, R., M. Lockwood, M. N. Wild, and T. D. G. Clark, Solar causes of the long-term increase in geomagnetic activity, J. Geophys. Res., 104, 28325–28342, 1999.

    Article  Google Scholar 

  • Svalgaard, L. and E. W. Cliver, The IDV index: Its derivation and use in inferring long-term variations of the interplanetary magnetic field strength, J. Geophys. Res., 110, A12103, doi:10.1029/2005JA011203, 2005.

    Article  Google Scholar 

  • Tobiska, W. K., T. Woods, F. Eparvier, R. Viereck, L. Floyd, D. Bouwer, G. Rottman, and O. R. White, The SOLAR2000 empirical solar irradiance model and forecast tool, J. Atmos. Solar-Terr. Phys., 62(14), 1233–1250, 2000.

    Article  Google Scholar 

  • Vogt, J., B. Zieger, A. Stadelmann, K.-H. Glassmeier, T. I. Gombosi, K. C. Hansen, and A. J. Ridley, MHD simulations of quadrupolar paleomagnetospheres, J. Geophys. Res., 109, A12221, doi:10.1029/2003JA010273, 2004.

    Article  Google Scholar 

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Correspondence to Susan Macmillan.

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Macmillan, S., Droujinina, A. Long-term trends in geomagnetic daily variation. Earth Planet Sp 59, 391–395 (2007).

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Key words

  • Geomagnetism
  • daily variations