Points of controversy in the study of magnetic storms

In the present review we concentrate on the most important and so far unresolved problems concerning morphology and physics of magnetic storms, namely, 1) which currents are responsible for the Dst variation; 2) which geophysical factors control the Dst index and what the underlying physics is; 3) why the latitude of the auroral electrojets and energetic particle precipitation region decreases during storms; 4) if there actually is a storm-to-substorm relation. We present major experimental results and theoretical views on each of the above problems.