The enhancement of the equatorial electrojet during polar magnetic substorms

It is shown that the growth of auroral electrojects can greatly enhance the equatorial electro jet. This indicates that a part of the return current, spreading from the auroral zone to the ionosphere in low and middle latitudes, can extend to as far as the late afternoon side along the magnetic equator. The current systems inferred so far for polar magnetic substorms may have to be revised to include such an intense return current. The enhancement is used to infer the distribution of the highly conductive region along the magnetic equator. It is shown that the conductivity is about 4–7 times higher there than in middle latitudes.