Figure 2

Intense PsA recorded in Scandinavia on March 29, 2017 (Case A). (a–d) Successive auroral images from Sodankylä (SOD) and Kevo (KEV), Finland, sampled every ~4 minutes from 00:04:00 to 00:16:00 UT. The original images were mapped to the geographic coordinates assuming an emission height of 110 km. The blue dot in each panel represents Arase’s magnetic footprint estimated using an empirical magnetic field model of the Earth’s magnetic field²⁶. The green dot indicates the point at which we obtained the highest cross-correlation coefficient between the chorus intensity from Arase and the auroral luminosity (the detailed procedures to derive this point are provided in the Material and Methods section of the Supplementary Material). (e) A time-series of optical intensity along the south-to-north cross-section, including the maximum cross-correlation point (MAX CCC), denoted by the horizontal green line. The cross-section is shown in the upper four panels by the vertical green line. (f) A frequency-time diagram of the electric field’s power spectral density from the Arase satellite showing lower-band chorus wave activity. The two horizontal white lines represent 0.5f_ce and 0.1f_ce at the magnetic equator.