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Two-dimensional (2D) aurora images with full spectrum have been captured by scientists in Japan using the newly-developed hyperspectral camera for auroral imaging (HySCAI).
Keogram of (a) all-sky camera and (b) HySCAI, and (c) time evolution of space-averaged spectrum of aurora emission measured by HySCAI on October 20-21, 2023. Image credit: Yoshinuma et al., doi: 10.1186/s40623-024-02039-y.
The aurora is a natural luminous phenomenon caused by interactions between precipitating particles and the constituents of the upper atmosphere.
Most of the observed spectrum consists of lines or bands of neutral or ionized nitrogen and oxygen atoms.
There is a variety of characteristic colors of aurorae, such as green and red, but there are multiple theories about the emission process by which they appear in different types of aurorae, and to understand the colors of aurorae, the light must be broken down.
Comprehensive (temporal and spatial) spectral observations are needed to study auroral emission processes and colors in detail.
“We’ve been observing the emission of light from plasma in a magnetic field in the Large Helical Device (LHD),” said Dr. Katsumi Ida from Japan’s National Institute for Fusion Science and colleagues.
“Various systems have been developed to measure the spectrum of light emitted from the plasma, and the processes of energy transport and atomic and molecular emission have been studied.”
“By applying this technology and knowledge to auroral observations, we can contribute to the understanding of auroral luminescence and the study of the energy production process of electrons that gives rise to auroral luminescence.”
The newly-developed camera, HySCAI, consists of an all-sky lens, monitor camera, galvanometer scanner, grating spectrograph, and electron multiplying charge coupled device.
“Aurora observation uses optical filters to obtain images of specific colors, which has the disadvantage of a limited acquisition wavelength with low resolution,” the researchers said.
“On the other hand, a hyperspectral camera has the advantage of obtaining a spatial distribution of the spectrum with high wavelength resolution.”
“We started a plan to develop a high-sensitivity hyperspectral camera in 2018 by combining a lens spectrometer with an EMCCD camera, which had been used in the LHD, with an image-sweep optical system using galvanometer mirrors.”
“It took five years from the planning stage to develop a highly sensitive system capable of measuring aurorae at 1kR (1 kilo-Rayleigh).”
“In May 2023, this system was installed at Swedish Space Corporation’s Esrange Space Center in Kiruna, Sweden, which is located just below the auroral belt and can observe aurorae with high frequency.”
“The system succeeded in acquiring hyperspectral images of the aurorae, that is, two-dimensional images of them broken down by wavelength.”
The team’s work was published in the journal Earth, Planets and Space.
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M. Yoshinuma et al. 2024. Development of hyperspectral camera for auroral imaging (HySCAI). Earth Planets Space 76, 96; doi: 10.1186/s40623-024-02039-y
