Mid-Latitude Daytime F₂-Layer Disturbance Mechanism under Extremely Low Solar and Geomagnetic Activity in 2008–2009

• Main Authors: Andrey V. Mikhailov, Loredana Perrone, Anatoly A. Nusinov
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Remote Sensing
• Subjects: quiet-time F₂-layer disturbances; sudden stratospheric warming; retrieved thermospheric parameters
• Online Access: https://www.mdpi.com/2072-4292/13/8/1514
• ISSN: 2072-4292

European near-noontime ionosonde observations were considered during the period of deep solar minimum in 2008–2009 to analyze f_oF₂ perturbations not related to solar and geomagnetic activity. Sudden stratospheric warming (SSWs) events in January 2008 and 2009 were analyzed. An original method was used to retrieve aeronomic parameters from observed electron concentration in the ionospheric F-region. Atomic oxygen was shown to be the main aeronomic parameter responsible both for the observed day-to-day and long-term (during SSWs) f_oF₂ variations. Atomic oxygen rather than neutral temperature mainly controls the decrease of thermospheric neutral gas density in the course of the SSW events. Day-to-day variations of thermospheric circulation and an intensification of eddy diffusion during SSWs are suggested to be the processes changing the atomic oxygen abundance in the upper atmosphere for the periods in question. Recent Global-Scale Observations of the Limb and Disk (GOLD) observations of O/N₂ column density confirm the depletion of the atomic oxygen abundance not related to geomagnetic activity during SSWs.