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2 Acta Geophysica

2 2014

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Mesospheric temperatures derived from three decades of hydroxyl airglow measurements from Longyearbyen, Svalbard (78°N)

Holmen S.E, Dyrland M.E, Sigernes F.

Acta Geophysica

2014

Vol. 62, no. 2

302--315

The airglow hydroxyl temperature record from Longyearbyen, Svalbard, is updated with data from the last seven seasons (2005/20062011/2012). The temperatures are derived from ground-based spectral measurements of the hydroxyl airglow layer, which ranges from 76 to 90 km height. The overall daily average mesospheric temperature for the whole temperature record is 206 K. This is by 3 K less than what Dyrland and Sigernes (2007) reported in their last update on the temperature series. This temperature difference is due to cold winter seasons from 2008 to 2010. 2009/2010 was the coldest winter season ever recorded over Longyearbyen, with a seasonal average of 185 K. Temperature variability within the winter seasons is investigated, and the temperature difference between late December (local minimum) and late January (local maximum) is approximately 8 K.

Cosmic factors influence on the inter-annual variations of the green 557.7 Nm line and red 630.0 Nm line nightglow intensities and their possible coupling with cloud covering at Abastumani (41.75°N, 42.82°E)

Todua M., Didebulidze G.G.

Acta Geophysica

2014

Vol. 62, no. 2

381--399

We studied the inter-annual distributions of the nightglow intensities of the thermosphere atomic oxygen red 630.0 nm and green 557.7 nm lines observed from Abastumani during cloudless nights, the planetary geomagnetic Ap index, solar F10.7, and galactic cosmic rays (GCRs) flux. It is demonstrated that: on magnetically weakly disturbed/ quiet conditions (Ap < 12) in equinoctial months the red line intensities are minimal, while those of the green line are maximal; the red line intensity increases in May–July and is comparatively low in June, where, unlike most mid-latitude regions, the green line intensity is maximal. The red and green line intensities increase with growing solar activity but their behaviors stay the same, which is considered as a possible regional manifestation of lower and upper atmosphere vertical coupling. It was also detected that, for cloudless nights in June, the number of magnetically disturbed day-nights is maximal and the decrease of the GCRs flux is the biggest during a year.