Abstract
In recent years, aurora observation networks using high-sensitivity cameras have been developed in the polar regions. These networks allow dimmer auroras such as pulsating auroras (PsAs) to be observed with a high signal-to-noise ratio. We reconstructed the horizontal distribution of precipitating electrons using computed tomography with monochromatic PsA images obtained from three observation points. The three-dimensional distribution of the volume emission rate (VER) of the PsA was also reconstructed. The characteristic energy of the reconstructed precipitating electron flux ranged from 6 keV to 23 keV, and the peak altitude of the reconstructed VER ranged from 90 to 104 km. We evaluated the results using a model aurora and compared the model’s electron density with the observed electron density. The electron density was reconstructed correctly to some extent, even after a decrease in PsA intensity. These results suggest that the horizontal distribution of precipitating electrons associated with PsAs can be effectively reconstructed from ground-based optical observations.
Highlights
Aurora computed tomography (ACT) is a method for reconstructing the three-dimensional (3-D) volume emission rate (VER) of auroral emission based on monochromatic auroral images obtained from multiple observation points (e.g., Aso et al, 1990). 30 The horizontal distribution of precipitating electron flux can be simultaneously obtained by ACT without rocket or satellite observations (Tanaka et al, 2011)
The ACT method is 135 helpful for investigating pulsating auroras (PsAs)-associated temporal variations in the horizontal distribution of precipitating electrons without rocket or satellite observations. 3.3 Volume emission rate Figure 4a shows the 3-D distributions of VERs derived from the reconstructed electron flux by solving the forward problem
4 Conclusions We applied the ACT method to PsA patches for the first time and reconstructed the horizontal distribution of precipitating electrons from 427.8-nm auroral images obtained from three observation points
Summary
Aurora computed tomography (ACT) is a method for reconstructing the three-dimensional (3-D) volume emission rate (VER) of auroral emission based on monochromatic auroral images obtained from multiple observation points (e.g., Aso et al, 1990). 30 The horizontal distribution of precipitating electron flux can be simultaneously obtained by ACT without rocket or satellite observations (Tanaka et al, 2011). 30 The horizontal distribution of precipitating electron flux can be simultaneously obtained by ACT without rocket or satellite observations (Tanaka et al, 2011). It has been difficult to apply ACT to PsAs because the signal-to-noise ratio (SNR) of PsA images is lower than those of discrete aurora images. A WMI consists of a highly 45 sensitive CCD camera made by Watec Co., Ltd (Japan). These cameras are suitable for studying very faint auroral structures such as PsAs. In this study, we attempted to use these high-sensitivity cameras and ACT methods to reconstruct the 3-D VER of a PsA and the horizontal distribution of precipitating electrons for the first time
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