GPS L1 signals absorption in high-latitude lower ionosphere during severe geomagnetic storm in June 2015

Abstract

Based on the results of an analysis of FORMOSAT-3/COSMIC radio occultation measurements, the absorption of DM-radio waves (wavelength ∼19 cm) in the lower high-latitude ionosphere of the Earth was detected. The maximum absorption value is ∼3 dB in the range from ∼60 to ∼90 km and, in some cases, it reaches ∼10 dB at altitudes from ∼90 to ∼95 km. A method for determining the vertical profiles of the absorption coefficient by solving the inverse problem of radiosonding in the Earth’s lower ionosphere is proposed. The absorption layers, caused by powerful bursts of X-ray radiation and strong changes in geomagnetic conditions during the storm, were reliably identified in individual sessions. It was found that, at altitudes from ∼90 to ∼100 km, the value of the absorption coefficient of DM-radio waves reached values (5.69 ± 1.35)·10−3 dB/km.