5:15 PM - 7:15 PM
[PEM12-P17] Variations of OH airglow intensity before and after energetic particle precipitation events
Keywords:Polar mesopause, OH airglow, Aurora, Ground-based spectral observation, Antarctic
We have been conducting spectral observations of OH (8-4) airglow which is emitted at an altitude of approximately 86 km, at Syowa Station during the winter season. From these observations, we derived the rotational line intensity of OH (8-4) airglow (OH airglow intensity) and the rotational temperature. This study investigates the effects of energetic particle precipitation (EPP) into the middle atmosphere in the mesopause region during auroral activity. It is believed that EPP produces NOx and HOx in the upper atmosphere, which subsequently leads to the destruction of ozone molecules. Therefore, OH airglow intensity is expected to fluctuate due to changes in atmospheric composition in the upper polar mesosphere associated with EPP.
We extracted EPP events from imaging riometer observation data at Syowa Station from 2016 to 2023 (and in May 2024). We defined EPP events as instances where cosmic radio noise absorption (CNA) values exceeded 1.0 dB, even momentarily. All sky image data taken by color digital cameras at Syowa Station were used to check nightly weather conditions and aurora activities. There were 16 nights when EPP events occurred and high-quality OH spectral data were available. These data were used for a superposed epoch analysis. The time when CNA values exceeded 1.0 dB was defined as time zero, and OH spectral data from one hour before and after this time were superposed. The OH airglow intensity peaked a few minutes after the CNA value first exceeded 1.0 dB, then decreased afterward and appeared to return to approximately the same level as before.
In this presentation, we present the analysis results of OH (8-4) airglow spectral data observed at Syowa Station from 2016 to 2018 and 2021 to 2024. We discuss variations in OH airglow intensity associated with EPP events and their mechanisms, with a particular focus on data obtained in May 2024.
We extracted EPP events from imaging riometer observation data at Syowa Station from 2016 to 2023 (and in May 2024). We defined EPP events as instances where cosmic radio noise absorption (CNA) values exceeded 1.0 dB, even momentarily. All sky image data taken by color digital cameras at Syowa Station were used to check nightly weather conditions and aurora activities. There were 16 nights when EPP events occurred and high-quality OH spectral data were available. These data were used for a superposed epoch analysis. The time when CNA values exceeded 1.0 dB was defined as time zero, and OH spectral data from one hour before and after this time were superposed. The OH airglow intensity peaked a few minutes after the CNA value first exceeded 1.0 dB, then decreased afterward and appeared to return to approximately the same level as before.
In this presentation, we present the analysis results of OH (8-4) airglow spectral data observed at Syowa Station from 2016 to 2018 and 2021 to 2024. We discuss variations in OH airglow intensity associated with EPP events and their mechanisms, with a particular focus on data obtained in May 2024.