Seasonal and solar cycle variations of night-time anomalous enhancements in total electron content

Seasonal and solar cycle variations of the various characteristics of night-time anomalous enhancements in total electron content (TEC) of the ionosphere are presented for a low latitude station, Hawaii by considering TEC data for a full solar cycle. All the characteristics of the TEC enhancements have seasonal and solar cycle dependence. TEC enhancement characteristics such as frequency of occurrence, amplitude and duration are positively correlated with solar activity. The possible source mechanisms for the observed enhancements are also discussed.