Articles | Volume 41, issue 1
Regular paper
16 Jan 2023
Regular paper |  | 16 Jan 2023

Storm time polar cap expansion: interplanetary magnetic field clock angle dependence

Beket Tulegenov, Joachim Raeder, William D. Cramer, Banafsheh Ferdousi, Timothy J. Fuller-Rowell, Naomi Maruyama, and Robert J. Strangeway

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Cited articles

Aikio, A. T., Pitkänen, T., Kozlovsky, A., and Amm, O.: Method to locate the polar cap boundary in the nightside ionosphere and application to a substorm event, Ann. Geophys., 24, 1905–1917,, 2006. a
Aikio, A. T., Pitkänen, T., Honkonen, I., Palmroth, M., and Amm, O.: IMF effect on the polar cap contraction and expansion during a period of substorms, Ann. Geophys., 31, 1021–1034,, 2013. a
Blanchard, G. T., Lyons, L. R., Samson, J. C., and Rich, F. J.: Locating the polar cap boundary from observations of 6300 Åauroral emission, J. Geophys. Res., 100, 7855,, 1995. a
Browett, S. D., Fear, R. C., Grocott, A., and Milan, S. E.: Timescales for the penetration of IMF By into the Earth's magnetotail, J. Geophys. Res., 122, 579–593,, 2017. a
Cowley, S. W. H.: The causes of convection in the Earth's magnetosphere: A review of developments during the IMS, Reviews of Geophysics, 20, 531,, 1982. a, b
Short summary
We study how the polar regions of the Earth connect to space along magnetic field lines. While the Earth's magnetic field is mostly the shape of a dipole, at high latitudes the field lines tend to be open and connect to interplanetary space. This area of open field line is called the polar cap, and it is highly dynamic. Through data analysis and computer simulations, we find that the shape of the polar cap is closely controlled by the magnetic field embedded in the solar wind.