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

K. Niranjan (1) , P. S. Brahmanandam (1) , P. Ramakrishna Rao (1) , G. Uma (1) , D. S. V. V. D. Prasad (1) , P. V. S. Rama Rao (1)

1 Department of Physics

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).

Domaines: Océan, Atmosphère; Sciences de la Terre

K. Niranjan, P. S. Brahmanandam, P. Ramakrishna Rao, G. Uma, D. S. V. V. D. Prasad, et al.. Post midnight spread-F occurrence over Waltair (17.7° N, 83.3° E) during low and ascending phases of solar activity. Annales Geophysicae, 2003, 21 (3), pp.745-750. ⟨hal-00317019⟩