Abstract:
We have studied aurora computed tomography, which is a method to reconstruct three-dimensional (3-D) structure of auroral luminosity from multiple auroral monochromatic images simultaneously obtained by network observation, in cooperation with the Swedish Institute of Space Physics. As an evolution of this method, we present a generalized aurora computed tomography (G-ACT) that retrieves differential flux of incident auroral electrons from a variety of observational data, such as electron density enhancement from the EISCAT radar, cosmic noise absorption (CNA) from imaging riometer, as well as the auroral monochromatic images. In this study, we evaluate feasibility of the G-ACT by numerical simulation.
Assuming the energetic and spatial distributions of incident electrons at 300 km over the EISCAT radar site, we solve the forward problem. The forward analysis involves the model calculations of electron density enhancement and auroral emission for assumed incident electrons and the mapping of the results to the instruments, i.e., ALIS (Auroral Large Imaging System) cameras, the EISCAT radar, and the imaging riometer at Kilpisjarvi. The obtained auroral images, electron density profile, and CNA are used for the inversion analysis. The inversion analysis is based on the constrained least squares method. The hyper-parameters corresponding to weight of each data are determined by the cross-validation method. The results indicate that this method is capable of reconstructing total energy flux and characteristic energy of incident auroral electrons. Since recent observations are conducted with various instruments, the G-ACT will be a valuable method for studying auroral phenomena in the near future.
