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Earth, Planets and Space
Fig. 2 | Earth, Planets and Space

Fig. 2

From: Latitudinal and interhemispheric differences of the ionospheric semi-diurnal lunitidal perturbations during the 2009 Arctic sudden stratospheric warming event in the eastern Asia–Australia sector

Fig. 2

The stratospheric polar temperature and wind, the planetary wave activity, and the solar and geomagnetic indices as a function of cumulative days from 1 January 2009. a T (red) is the temperature at 90°N, 10 hPa and U is the zonal mean zonal wind at 60°N, 10 hPa. The vertical dashed lines mark the initiation dates of the decrease and reversal of U. b Z1 and Z2 are the planetary-wave amplitudes of zonal wavenumber 1 and 2 components, respectively, calculated from the geopotential height at 60°N, 10 hPa. c The Kp (blue) and F10.7 (red) indices

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