Abstract
Abstract. The auroral emission of the first negative system of N2+ at 427.8 nm is analyzed using simultaneous measurements from the ground with ALIS (Auroral Large Imaging System) and from space with optical (MAC) and particle (ESA) instruments of the Reimei satellite. The study has two main objectives. The first is validation of the absolute calibration of the ALIS and the Reimei MAC cameras. The other task is to evaluate different cross sections of the electron excitation of N2+ that are used for the modeling of the auroral 1N system emissions. The simultaneous measurements of the 427.8 nm emission by ALIS and Reimei imagers show excellent agreement, indicating that the calibration of the two instruments is correct. Comparison of the 427.8 nm emission intensity calculated using the incident electron flux measured by the Reimei particle instruments with intensities measured by the optical imagers show that the best match is reached with the cross section from Shemansky and Liu (2005).
Highlights
The auroral 427.8 nm emission, produced by the transition from the N+2 (B2 u+) state to the first vibrational level of the ground state N+2 (X2 g+), is caused by simultaneous electron impact ionization and excitation of molecular nitrogen in the ionosphere, and is one of the best understood emissions
The objective of this study is to use simultaneous measurements of the intensity of the 427.8 nm 1 NG emission from ALIS (Auroral Large Imaging System) and the intensity and electron flux from the Reimei satellite to intercalibrate the optical and particle measurements, and to evaluate different sets of cross sections and spectroscopic parameters to find the best fit to the experimental data
The satellite is in a sun-synchronous orbit at an altitude of about ∼ 630 km. It carries a payload consisting of Electron/Ion energy Spectrum Analysers (ESA/ISA) (Asamura et al, 2003) and a Muti-Spectral Auroral Imaging Camera (MAC) (Obuchi et al, 2008; Sakanoi et al, 2003), which enables it to make multi-spectral optical measurements of the aurora and the precipitating particles simultaneously
Summary
The auroral 427.8 nm emission, produced by the transition from the N+2 (B2 u+) state to the first vibrational level of the ground state N+2 (X2 g+), is caused by simultaneous electron impact ionization and excitation of molecular nitrogen in the ionosphere, and is one of the best understood emissions. The strong discrepancies between the observed and calculated results were demonstrated The authors attributed this disagreement to the possible input of the other auroral emissions in the measured intensity as well as to the effect of the ground albedo, which is difficult to take into account in the calculations. The objective of this study is to use simultaneous measurements of the intensity of the 427.8 nm 1 NG emission from ALIS (Auroral Large Imaging System) and the intensity and electron flux from the Reimei satellite to intercalibrate the optical and particle measurements, and to evaluate different sets of cross sections and spectroscopic parameters to find the best fit to the experimental data
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