Characteristic of Sporadic-E over the anomaly crest region during the low solar cycle

Abstract

The paper describes the nature of Sporadic E layer over anomaly crest region Bhopal, (Geo.Lat.23.2° N, Geo. Long77.4° E, and Dip latitude18.4 °) over a four year period covering the ending phase of 23rd Solar Cycle and starting phase of 24th solar cycle. This particular period is felt to be very suitable for examining the sunspot number and it encompasses periods of low solar activities. We also included the space weather activities along with it. We have taken auroral electrojet index (AE) and, disturbed storm time index (Dst) to characterize the storm intensity. The sunspot number (Rz) and solar flux (F10.7) described of solar activities. The occurrence probability of Sporadic- E, layer is highest in summer solstice, moderate during equinox and low during winter solstice. Remarkable occurrence peaks appear from June to July in summer and from December to January in winter. The layer occurrence showed a double peak variation with distinct layer groups, in the morning and the other during evening .The morning layer descent was associated with layer density increase indicating the strengthening of the layer while it decreased during the evening layer descent. The result indicates the presence of semi-diurnal tide over the location while the higher descent velocities could be due to the modulation of the ionization by gravity waves along with the tides. The irregularities associated with the gradient-drift instability disappear during the counter electrojet and the current flow is reversed in westward.