Auroral spectral estimation with wide-band color mosaic CCDs

Abstract

Abstract. Color mosaic CCDs use a matrix of different wide-band micro-filters in order to produce images with several (often three) color channels. These devices are increasingly employed in auroral studies to provide time sequences of two dimensional luminosity maps, but the color information is typically only used for qualitative analysis. In this study we use Backus–Gilbert linear inversion techniques to obtain quantitative measures of effective spectral resolution for multi-channel color mosaic CCDs. These techniques also allow us to explore the possibility of further improvements by modifying or combining multiple detectors. We consider two spectrally calibrated commercial color CCDs (Sony ICX285AQ and ICX429AKL) in order to determine effective wavelength resolution of each device individually, together, and with additional filters. From these results we develop methods to enhance the utility of existing data sets, and propose ways to improve the next generation of low-cost color auroral imaging systems.

On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

“…The Canadian network of Rainbow operates with 5 s exposure at a 6 s cadence. Rainbow data include three color channels (red, green, and blue) that can be used to evaluate the ratio among the three color components of the auroras, which may bear some information on the flux spectral property of the precipitation [ Jackel et al ., ]. In particular, as one can see from Figures 2 and 3 in Jackel et al .…”

“…In particular, as one can see from Figures 2 and 3 in Jackel et al . [], the channel passbands of Rainbow CCD, although rather wide, are purposely designed to preferentially select 630 and 558 nm. The red‐to‐green intensity ratio of Rainbow is thus to be used in this study as a qualitative indicator of the relative strength of the red‐line aurora as compared to the green‐line one.…”

“…We have made preliminary test on the spectral filters of Rainbow and deduced that as long as the red‐to‐green ratio is ≥1/3, the red‐channel data number seen by Rainbow is unlikely to be mainly contributed by a passband leakage from auroral emission lines other than 630 nm. Therefore, the red‐to‐green ratio may deliver some information on the relative brightness of the red‐line aurora and in turn the “softness” of precipitation flux spectrum [ Jackel et al ., ]. For the patches shown in Figures and , we note that the red‐to‐green ratio shows a noticeable increase during each on time of the patch.…”