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

Abstract

[1] The effects of induction electric field on ionospheric current systems driven by fieldaligned currents of magnetospheric origin were studied, and a new method for estimating the equivalent current function representing the system was developed. It was found that a current system with a period of less than 4 min is significantly affected by the induction field and tends to be symmetric with noon, probably because the field overcomes the electrostatic field that creates the asymmetry. This result is consistent with the observed result for the preliminary impulse of storm commencement in which the local time variation of its appearance is symmetric with noon.Citation: Takeda, M. (2008), Effects of the induction electric field on ionospheric current systems driven by field-aligned currents of magnetospheric origin,

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

“…Especially the induced FAC are often comparable to the non-inductive FAC, and may thus significantly modify the coupling between the ionosphere and magnetosphere in the most dynamical situations. Takeda (2008) found that global current systems with a period of less than 4 min are significantly affected by the induction field. The model results are consistent with the observed characteristics of the preliminary impulse of storm commencement.…”

“…Also the analysis method developed by Takeda (2008) takes magnetospheric FAC distributions and ionospheric conductances as input data, but the mathematical approach is somewhat different from Vanhamäki (2010). Takeda (2008) represent the divergence-free current with a potential ψ J , as in Eq. (6), while the curl-free part of the current is expanded as a sum of simple vector systems equivalent to the CF SECS used by Vanhamäki (2010).…”

Inductive ionospheric solver for magnetospheric MHD simulations

“…Takeda (2008) solved a differential equation for the divergence-free current potential ψ defined in Eq. (7), but presented the curl-free part of the current as a sum of simple vector systems equivalent to the CF SECS used here.…”

“…More recently showed that in very dynamical situations, like in a westward traveling surge, induction may contribute up to 30% of the total electric field in some limited areas. Takeda (2008) concluded that induction may affect rapidly changing, global current systems, such as the preliminary impulse of storm commencement. These results suggest that ionospheric induction may have a non-negligible role in magnetosphere-ionosphere coupling, especially during active periods such as substorm onsets.…”

Strong induction effects during the substorm on 27 August 2001

“…Large values of dB/dt, associated closely with GICs, occur in the regions of westward ionospheric electrojets (Boteler and Pirjola 1998;Vodyannikov et al 2006;Vanhamäki and Amm 2011;Viljanen and Tanskanen 2011;Zhang et al 2012). Short-period geomagnetic variations (geomagnetic pulsations) with periods τ ≤ 100 − 200 s change the ionosphere's impedance, lead to the partial penetration of induction electric fields carried by MHD waves, affect the formation of double layers and beams of energetic particles, and reduce the dawn-dusk asymmetry in the distribution of ionospheric currents (Lotko 2004;Takeda 2008;Vanhamäki and Amm 2011). Various aspects of the induction effects during substorms have also been discussed (Akasofu 1975;Alfven 1977;Lyatsky 1978;Liu et al 1988;Shelomentsev et al 1988;Sanches et al 1991;Lockwood and Davis 1999;Heikkila et al 2001;Tang et al 2010;Gordeev et al 2011;Siscoe et al 2012).…”