Effects of the induction field on the Sq dynamo currents in the ionosphere

Abstract

[1] Effects of the induction field on the ionospheric currents generated by the Sq dynamo were studied using current function. It was shown that the induction field significantly affects the ionospheric currents only if the field is artificially enhanced by 100 times. Existence of the spherical inner conductor reduces the effects because currents induced in the sphere partly cancel vertical component of the variation field. On the other hand, it is probable that the induction field should be considered for the simulation of the ionospheric current with the period of less than 10 min. because the induction field affects the ionospheric Sq currents if the field is enhanced by 100 times.Citation: Takeda, M. (2005), Effects of the induction field on the Sq dynamo currents in the ionosphere,

Effects of the induction electric field on ionospheric current systems driven by field‐aligned currents of magnetospheric origin

“…The basic equations are the same as those by Takeda [2005], using the “thin shell” approximation introduced by Van Sabben [1962]. In this approximation the ionosphere is treated as an infinitely thin shell, and the horizontal electric field and current are related using “two‐dimensional” conductivity.…”

“…From , , and the equation determining ψ is obtained as follows: where In addition, J G θ and J G ϕ are the components of J G . B r can be related to ψ by using spherical harmonics expansion [ Takeda , 2005].…”

“…It is assumed that there exists an internal spherical conductor that represents the solid Earth and that the conductivity is uniformly 1 S/m and the depth is 500 km. These values are the same as those used by Takeda [2005]. The field‐aligned current model used in the present study is similar to that used by Takeda [1982].…”

“…In the present simulation we primarily consider the effect of the induction field, and therefore the current is assumed to flow vertically to avoid complications. The periods of the variation are selected to be 60, 10, 4, and 1 min because Takeda [2005] suggested that the induction field becomes significant for the variations in these periods.…”

“…Therefore any ionospheric current system having a short period will be significantly affected by the induction field generated by itself. Takeda [2005] estimated the effects of the self‐induction electric field on the ionospheric Sq current system and showed that they are significant if the field is artificially enhanced by 100 times. This suggests that ionospheric currents causing rapid geomagnetic field variation of a period of less than 10 min are significantly affected by the induction field.…”