Why does the cold air behind a cold front tend to move south-eastwards while the warm air behind a?

The motor effect means an electric current flows at a right angle to a magnetic field and that produces a force at right angles to the current and the field. Charged particles from the sun light up the sky causing what we call "northern lights". It also drives a wind around the north pole, called the jet wind, and that wind goes west to east. When the jet moves south, that is a cold front. When the jet moves north, that is a warm front.

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