Fig. 6From: Monitoring of equatorial plasma bubbles using aeronautical navigation system: a feasibility studya, b 630.0Â nm all-sky images obtained from Ishigaki Island, respectively, on the nights of Oct 31 and November 1, 2021. c, d S4 index obtained from a GNSS receiver in Ishigaki on the nights of Oct 31, and November 1, 2021Back to article page