Post midnight spread-F occurrence over Waltair (17.7° N, 83.3° E) during low and ascending phases of solar activity

• Main Authors: K. Niranjan, P. S. Brahmanandam, P. Ramakrishna Rao, G. Uma, D. S. V. V. D. Prasad, P. V. S. Rama Rao
• Format: Article
• Language: English
• Published: Copernicus Publications 2003-03-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/21/745/2003/angeo-21-745-2003.pdf

A study carried out on the occurrence of post midnight spread-F events at a low-latitude station, Waltair (17.7° N, 83.3° E), India revealed that its occurrence is maximum in the summer solstice months of the low solar activity period and decreases with an increase in the sunspot activity. The F-region virtual height variations show that 80% of these spread-F cases are associated with an increase in the F-region altitude. It is suggested with the support of the night airglow 6300 A zenith intensity data obtained with co-located ground-based night airglow photometer and electron temperature data from the Indian SROSS C2 satellite that the seasonal variation of the occurrence and probable onset times of the post midnight spread-F depend on the characteristics of the highly variable semipermanent equatorial Midnight Temperature Maximum (MTM).<br><br><b>Key words. </b>Ionosphere (ionospheric irregularities; ionosphere atmosphere interactions) Atmospheric composition and structure (airglow and Aurora)