Sporadic- E and the equatorial electrojet

Abstract

An analysis of characteristics of sporadic- E at Indian and American equatorial stations has been made for quiet and disturbed days during the year 1958. The analysis reveals certain differences between the two chains of stations which indicate a possible difference in the width of the equatorial electrojet at the two zones. In both the annual and seasonal variations on quiet days, values of Es are always higher at Indian stations. Disturbed day value of ƒEs is lower than on quiet day. Latitudinal variation of the noon ƒEs on quiet and disturbed days has been drawn for both the zones and a difference in the two zones found to occur. In addition, it is observed from the superposed epoch method of analysis for disturbed days, ƒEs shows a drop compared to the quiet day values and the amount of drop is reduced as one goes away from the magnetic equator. Corresponding dips are found in the values of the horizontal component of the earth's magnetic field. The differences observed in the two zones, possibly due to the effect of the equatorial electrojet are pointed out. The percentage occurrence of Es also shows characteristic diurnal variation in all seasons at the two zones. The latitudinal variation of the percentage occurrence of Es shows considerable differences indicative of a possible difference in the width of the electrojet at the two areas. The variation of noon ƒEs with sunspot activity for Indian stations shows that there is an increase in ƒEs with increase in sunspot number. The increase up to a sunspot number of about 100 is not much; but afterwards the rise is fairly rapid and linear up to a very high sunspot number. This is compared with the corresponding ƒ oF2 variations which show saturation effects after a sunspot number of about 120.