The electric currents exist because the molten iron is a good electrical conductor and is undergoing convective stirring as it passes its heat upwards into the overlying solid mantle.
(The electric currents; exist; because the molten iron is a good electrical conductor and is undergoing convective stirring) (the molten iron; is; a good electrical conductor)
The electric currents the molten iron
exist is
because the molten iron is a good electrical conductor and is undergoing convective stirring
a good electrical conductor