11:00 AM - 11:15 AM
[PEM10-02] Reconstruction of the three-dimensional ionospheric conductivity using Aurora Computed Tomography
Keywords:Pulsating aurora, Electric conductivity, Tomography, Field-aligned current, Ionosphere
The three-dimensional (3-D) current system is essential to understand the Magnetosphere-Ionosphere coupling process because they are connected through the filed-aligned current (FAC). The pulsating aurora (PsA), which typically has a patchy shape and quasi-periodic modulation in its luminosity with a time scale of seconds, emerges over a long time from around midnight to the morning side. In several previous studies, magnetic field observations by satellites showed that PsAs were accompanied by FACs. These FACs are thought to be driven by the inhomogeneity of the electric conductivity in the ionosphere. However, it is not completely clear which part of the PsA the FACs associated with the PsA flow and how they are closed in the ionosphere. One reason for this is the difficulty in observing the ionospheric conductivity of PsAs, which fluctuates within seconds. Ground-based observations are useful for studying the 3-D current system of PsAs, which have a long appearance time and a large time variability. This study aims to reconstruct the 3-D distribution of ionospheric conductivity from monochromatic auroral images acquired by all-sky cameras installed at multiple ground-based stations using Aurora Computed Tomography (ACT).
First, we reconstructed the 3-D distribution of volume emission rate from the auroral images using ACT. We used 427.8 and 557.7 nm auroral images. The 427.8 nm auroral images were obtained at Abisko (68.36°N, 18.82°E), Kilpisjärvi (69.05°N, 20.78°E), and Skibotn (69.35°N, 20.36°E) while the 557.7 nm ones at Kilpisjärvi, Skibotn, and Tromsø (69.58°N, 19.23°E). The temporal resolution was 2 seconds. Second, we derived the 3-D distribution of ionospheric electron density from the volume emission rate using the continuity equation of electron density. Finally, the 3-D Pedersen and Hall conductivities were reconstructed by combining the neutral atmosphere model MSIS. We also quantitatively evaluated the FAC by the inhomogeneity of the electric conductivities under the assumption that the ionospheric electric field was uniform. We will show the analysis results for some PsA events in the presentation.
First, we reconstructed the 3-D distribution of volume emission rate from the auroral images using ACT. We used 427.8 and 557.7 nm auroral images. The 427.8 nm auroral images were obtained at Abisko (68.36°N, 18.82°E), Kilpisjärvi (69.05°N, 20.78°E), and Skibotn (69.35°N, 20.36°E) while the 557.7 nm ones at Kilpisjärvi, Skibotn, and Tromsø (69.58°N, 19.23°E). The temporal resolution was 2 seconds. Second, we derived the 3-D distribution of ionospheric electron density from the volume emission rate using the continuity equation of electron density. Finally, the 3-D Pedersen and Hall conductivities were reconstructed by combining the neutral atmosphere model MSIS. We also quantitatively evaluated the FAC by the inhomogeneity of the electric conductivities under the assumption that the ionospheric electric field was uniform. We will show the analysis results for some PsA events in the presentation.