Geomagnetic solar-flare effect and ionospheric induction

The dynamo theory of the ionospheric current system during a solar flare is studied taking the vectro-potential term (i.e. the induction effect) into consideration. A realistic form for the ionospheric conductivity sigma(THETA) is used. It is noticed that the effect of the induction current is to introduce a time-lag of several minutes between the maximum phase of the crochet all over the world, as has been deduced by previous morphological analyses. It is further concluded from the calculation that the flare-time current pattern is distinctly different from an augmented Sq-field, as also observed by morphological analysts. (author)