It is commonly assumed that the aurora borealis (Northern Hemisphere) and aurora australis (Southern Hemisphere) are mirror images of each other because the charged particles causing the aurora follow the magnetic field lines connecting the two hemispheres. The particles are believed to be evenly distributed between the two hemispheres, from the source region in the equatorial plane of the magnetosphere. Although it has been shown that similar auroral features in the opposite hemispheres can be displaced tens of degree in longitude1,2 and that seasonal effects can cause differences in global intensity3,4, the overall auroral patterns were still similar. Here we report observations that clearly contradict the common assumption about symmetric aurora: intense spots are seen at dawn in the Northern summer Hemisphere, and at dusk in the Southern winter Hemisphere. The asymmetry is interpreted in terms of inter-hemispheric currents related to seasons, which have been predicted5,6 but hitherto had not been seen.
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Østgaard, N. et al. Observations and model predictions of auroral substorm asymmetries in the conjugate hemispheres. Geophys. Res. Lett. 32 L05111 10.1029/2004GL022166 (2005)
Østgaard, N., Mende, S. B., Frey, H. U., Sigwarth, J. B., Aasnes, A. & Weygand, J. Auroral conjugacy studies based on global imaging. J. Atmos. Solar-Terr. Phys. (special issue) 69, 249–255 (2007)
Newell, P. T., Meng, C.-I. & Lyons, K. M. Suppression of discrete aurorae by sunlight. Nature 381, 766–767 (1996)
Liou, K., Newell, P. T., Meng, C.-I., Brittnacher, M. & Parks, G. Seasonal effects on auroral particle acceleration and precipitation. J. Geophys. Res. 106, 5531–5542 (2001)
Richmond, A. D. & Roble, R. G. Electrodynamic effects of therospheric winds from the NCAR thermospheric general circulation model. J. Geophys. Res. 92, 12365–12376 (1987)
Benkevich, L., Lyatsky, W. & Cogger, L. L. Field-aligned currents between the conjugate hemispheres. J. Geophys. Res. 105, 27727–27737 (2000)
Mende, S. B. et al. Far ultraviolet imaging from the IMAGE spacecraft. 2. Wideband FUV imaging. Space Sci. Rev. 91, 271–285 (2000)
Frank, L. A. et al. The Visible Imaging System (VIS) for the Polar spacecraft. Space Sci. Rev. 71, 297–328 (1995)
Stenbaek-Nielsen, H. C., Wescott, T. N., Davis, T. N. & Peterson, R. W. Auroral intensity differences at conjugate points. J. Geophys. Res. 78, 659–671 (1973)
Fillingim, M. O., Parks, G. K., Frey, H. U., Immel, T. J. & Mende, S. B. Hemispheric asymmetry of the afternoon electron aurora. Geophys. Res. Lett. 32 L03113 10.1029/2004GL021635 (2005)
Stubbs, T. J., Vondrak, R. R., Østgaard, N., Sigwarth, J. B. & Frank, L. A. Simultaneous observations of the auroral oval in both hemispheres under varying conditions. Geophys. Res. Lett. 32 L03103 10.1029/2004GL021199 (2005)
Heppner, J. P. & Meynard, N. C. Empirical high-latitude electric field models. J. Geophys. Res. 92, 4467–4489 (1987)
Cowley, S. W. H. Asymmetry effects associated with the X-component of the IMF in a magnettically open magnetosphere. Planet. Space Sci. 29, 809–818 (1981)
Sato, N., Nagaoka, T., Hashimoto, K. & Saemundsson, T. Conjugacy of isolated auroral arcs and non-conjugate auroral break-ups. J. Geophys. Res. 103, 11641–11652 (1998)
Lyatskaya, S., Lyatsky, W. & Khazanov, G. V. Relationship between substorm activity and magnetic disturbances in the two polar caps. Geophys. Res. Lett. 35 L20104 10.1029/2008GL035187 (2008)
Frank, L. A. & Sigwarth, J. B. Simultaneous images of the northern and southern auroras from the Polar spacecraft: an auroral substorm. J. Geophys. Res. 108 8015 10.1029/2002JA009356 (2003)
Frey, H. U. et al. Summary of quantitative interpretation of IMAGE Far Ultraviolet auroral data. Space Sci. Rev. 109, 255–283 (2003)
We are indebted to the IMAGE and Polar teams for the design and successful operations of the two missions. We especially thank S. B. Mende for the use of IMAGE FUV WIC data and J. B. Sigwarth for the use of Polar VIS Earth Camera data. This study was supported by the Norwegian Research Council, through the IPY-ICESTAR project 176045/S30
Author Contributions N.Ø is responsible for the project planning, K.M.L. is responsible for the data processing. The data were identified and analysed by K.M.L. and N.Ø. The manuscript was written by K.M.L. and N.Ø.
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Laundal, K., Østgaard, N. Asymmetric auroral intensities in the Earth’s Northern and Southern hemispheres. Nature 460, 491–493 (2009). https://doi.org/10.1038/nature08154
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