Imaging of polar cap patches with a low-cost airglow camera: pilot observations in Svalbard, Norway

Abstract

We evaluate the capability of a low-cost all-sky imager (ASI), which has been operative in Longyearbyen (78.1° N, 15.5° E), Norway, to detect 630.0 nm airglow signatures of polar cap patches. The ASI is composed of a small camera, with a charge-coupled device (CCD), manufactured by Watec Co. Ltd., a fish-eye lens, and an optical filter whose central wavelength is 632.0 nm and full-width half maximum (FWHM) is 10 nm. In Longyearbyen, another ASI equipped with a cooled electron-multiplying charge-coupled device (EMCCD) camera has been operative for observations of polar cap patches. We compare the images from the two systems and investigate the performance of the low-cost ASI. On the night of December 4, 2013, a series of polar cap patches were observed by the EMCCD ASI. The low-cost ASI also detected regions of enhanced 630.0 nm airglow passing through the fields-of-view. The quality of the raw images from the low-cost ASI obtained every 4 s were visibly much worse than that of the EMCCD ASI. However, an integration of 7-15 consecutive images made it possible to capture the temporal evolution and spatial structure of the patches, for example, their anti-sunward propagation and finger-like structures along the trailing edge. The estimated values of the absolute optical intensity from the low-cost ASI were found to be consistent with those from the EMCCD ASI, whereby the offset was < 100 R. This offset can be explained by the contribution of the background continuum emission to the low-cost ASI images, because the band width of the optical filter used for the low-cost ASI is ~ 3 times wider than that used for the EMCCD ASI. The results indicate that the airglow measurement with the low-cost ASI is feasible even for quantitative studies of F-region phenomena such as the dynamics of polar cap patches. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Dayside Transient Phenomena and Their Impact on the Magnetosphere and Ionosphere

“… 1984 ; Hosokawa et al. 2014 , 2016 , 2019 ). On the nightside the airglow patches leave the polar cap and enter the nightside auroral oval (Lorentzen et al.…”

“…Intense PMAF activity can also cause significant phase scintillation and loss of signal lock for satellite navigation signals . Recombination of the high-density plasma leads to weak 630.0 nm emissions that can be observed as airglow patches (Weber et al 1984;Hosokawa et al 2014Hosokawa et al , 2016Hosokawa et al , 2019. On the nightside the airglow patches leave the polar cap and enter the nightside auroral oval (Lorentzen et al 2004;Van Der Meeren et al 2015).…”

Observations of equatorial plasma bubbles using a low-cost 630.0-nm all-sky imager in Ishigaki Island, Japan

“…Similar small and low-cost ASIs have been deployed and installed into several places in the polar region in both hemispheres (Ogawa et al 2020). Hosokawa et al (2019) used one of the ASIs at Longyearbyen in Svalbard, Norway and confirmed its capability of detecting faint airglow signatures of polar cap patches whose airglow intensity is a few hundreds of Rayleigh. As a next step, we carried out a pilot observation at low latitudes to evaluate the feasibility of utilizing the ASIs for monitoring EPBs.…”

“…Hence, the derived absolute optical intensity in Rayleigh includes a certain contribution of background continuum emission. However, Hosokawa et al (2019) pointed out that the offset is ~ 20 R for the cases of airglow observations in the polar cap region.…”

“…Derivation of the absolute optical intensity in unit of Rayleigh has been done also using the calibration data obtained at NIPR. The procedure is documented in Hosokawa et al (2019) which employed the same imager for observing polar cap airglow patches in Longyearbyen (78.1° N, 15.5° E), Norway. When deriving the absolute optical intensity, we estimate the dark count using pixels outside the FOV of the ASI and subtract it from the raw count values.…”