Observations of plasma depletions in 557.7-nm images over Kavalur

摘要

An all sky imaging system was operated at Kavalur (12.56°N, 78.8°E, 4.6°N, geomagnetic), India, during February-April 2002. We observed plasma depletions in the 557.7- and 630.0-nm images in several nights and found that in most of the nights, the 557.7-nm depletions appeared around midnight and became very pronounced in the postmidnight hours. A simulation is carried out to understand the important physical parameters that influence the emissions of the 557.7 nm in various local times and solar activities, and that result in the appearance of depletions in the integrated images.