Solar flux influence on propagation of disturbance dynamo to equatorial ionosphere

Abstract

On some magnetically disturbed days equatorial ionospheric electric fields are changed which affects the quiet time behavior of equatorial F layer height in the post sunset hours. The effects seen at equatorial F region are either associated with disturbance dynamo (DD) or prompt penetration (PP) or combination of both DD and PP. In the present investigation an attempt is made to identify the effects associated with DD alone, which are causing upward movement of F layer in the post sunset hours and studied separately for low and high solar flux periods. Ionosonde data recorded at dip equatorial station Trivandrum (77° E, 8.5°N, dip0.5°N) for the period of 1990–2003 is scaled to obtained local time (LT) variation of base height of F layer (h'F) in the post sunset hours. Monthly quiet time average of h'F (〈h'F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</inf> 〉) is computed by taking 15 minutes average. Effect of DD electric field on h'F (ΔH) is computed by subtracting disturbed time h'F (h'F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf> ) from 〈h'F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</inf> 〈. The maximum enhancement seen in h'F due to DD electric field is obtained by taking minimum of ΔH and then compared with Joule energy deposited at high latitudes for different time lags. It is found that time delay required to produce the maximum effect of DD on equatorial F region height is solar flux dependent. The delay time is found to be higher for periods of high solar flux. Moreover the Joule energy required to produce same maximum upward movement of F layer as compared to their monthly quiet time pattern is found to be higher for days with high solar flux.