Abstract The spectrum of high‐altitude blue auroral emissions was observed with HyperSpectral camera for auroral imaging (HySCAI) during morning astronomical twilight in Kiruna. Auroral resonance scattering of an N2+ ${\mathrm{N}}{2}^{+}$ 1NG (0, 1) (427.8 nm) emission starts to increase from the east, and then the increase of this resonance scattering emission extends to the magnetic zenith. The volume emission rate is evaluated from the rise in resonance scattering emission (time derivative of emission intensity). The volume emission rate of N2+ ${\mathrm{N}}{2}^{+}$ (427.8 nm) reaches its maximum when the sunlight shadow height reaches 200 km, although the GLOW model predicted a peak altitude of N2+ ${\mathrm{N}}{2}^{+}$ (427.8 nm) of 120 km. The higher altitude of the resonance scattering emission peak observed with HySCAI supports the idea that N2+ ${\mathrm{N}}{2}^{+}$ is produced by the charge exchange between N2 ${\mathrm{N}}{2}$ and O+ ${\mathrm{O}}^{+}$ existing at high altitudes. However, we cannot rule out another possible mechanism of upflowing N2+ ${\mathrm{N}}{2}^{+}$ ions.
Observations from the Little Bunker
Last updated: November 30, 2025 04:25 AM
Atmospheric CO₂
426.8 ppm
+18.1
ppm/year
Atmospheric CH₄
1927.61 ppb
+2.73
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year