Ionospheric TEC, thermospheric cooling and Σ[O/N2] compositional changes during the 6–17 March 2012 magnetic storm interval (CAWSES II)

• Published in: Journal of atmospheric and solar-terrestrial physics 2014-08, Vol.115-116, p.41-51
• Main Authors: Verkhoglyadova, O.P., Tsurutani, B.T., Mannucci, A.J., Mlynczak, M.G., Hunt, L.A., Paxton, L.J.
• Format: Article
• Language: English
• Subjects: Geomagnetic storms; Ionosphere; Thermosphere
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2013.11.009

A series of four geomagnetic storms (the minimum SYM-H~−148nT) occurred during the March 6–17, 2012 in the ascending phase of the solar cycle 24. This interval was selected by CAWSES II for its campaign. The GPS total electron content (TEC) database and JPL's Global Ionospheric Maps (GIM) were used to study vertical TEC (VTEC) for different local times and latitude ranges. The largest response to geomagnetic activity is shown in increases of the low-latitude dayside VTEC. Several GPS sites feature post-afternoon VTEC “bite-outs”. During Sudden Impulse (SI+) event on March 8th a peak daytime VTEC restores to about quiet-time values. It is shown that the TIMED/SABER zonal flux of nitric oxide (NO) infrared cooling radiation correlates well with auroral heating. A factor of ~5 cooling increase is noted in some storms. The cooling radiation intensifies in the auroral zone and spreads towards the equator. Effects of the storm appear at lower latitudes ~18.6h later. The column density ratio Σ[O/N2] is analyzed based on TIMED/GUVI measurements. Both increases (at low latitudes) and decreases (from auroral to middle latitudes) in the ratio occurs during the geomagnetic storms. We suggest that the column density ratio could be enhanced at low to middle latitudes on the dayside partially due to the superfountain effect (atomic oxygen uplift due to ion-neutral drag). It is suggested that decreases in the Σ[O/N2] ratio at high to middle-latitudes may be caused by high thermospheric temperatures. During SI+s, there is an increase in Σ[O/N2] ratio at auroral latitudes. •Daytime ionospheric total electron content increased during the March 6–17, 2012 storms.•The TIMED/SABER zonal flux of nitric oxide (NO) infrared cooling radiation increased by a factor of about 5.•Cooling radiation increased at lower latitudes about 18.6h later than at auroral latitudes.•The column density ratio O/N2 increased at low latitudes and decreased from auroral to middle latitudes.•The column density ratio enhanced at low latitudes on the dayside possibly due to the superfountain effect.