GNSS Ionospheric Scintillations Observed in the Western Pacific Sector During the 1 December 2023 Geomagnetic Storm

A severe geomagnetic storm occurred on 1 December 2023. During this geomagnetic storm we found that strong ionospheric scintillations occurred from low-latitude to mid-latitude more than geomagnetic latitude 38° in the western Pacific sector along geomagnetic 170°W on 1 December 2023 by analyzing ground-based Global Navigation Satellite System (GNSS) observations. It is found that strong eastward penetration electric field (PEF) occurred from 10.12 to 13.12 UT (universal time) on 1 December 2023, corresponding to 18.12 to 21.12 LT (local time), i.e. the early evening period, in the western Pacific sector along geomagnetic 170°W. This intense eastward PEF mapped quickly along the geomagnetic field lines from high latitudes to the magnetic equator, and led to the occurrence of the intense eastward electric field from 10.12 to 13.12 UT on 1 December 2023 in the equatorial F region ionosphere along geomagnetic 170°W, which caused the uplifting of the equatorial F region ionosphere and provided suitable conditions for the growth of the generalized Rayleigh-Taylor instability (RTI), and then led to the occurrence of strong GNSS ionospheric scintillations in sequence from low-latitude to mid-latitude along geomagnetic 170°W in the northern and southern hemispheres on 1 December when GNSS ionospheric scintillations rarely occur in those regions.