  The dynamical relationship between magnetic storms and magnetospheric
substorms presents one of the most controversial problems of contemporary
geospace research. Here, we tackle this issue by applying a causal inference
approach to two corresponding indices in conjunction with several relevant
solar wind variables. We demonstrate that the vertical component of the
interplanetary magnetic field is the strongest and common driver of both,
storms and substorms, and explains their the previously reported association.
These results hold during both solar maximum and minimum phases and suggest
that, at least based on the analyzed indices, there is no statistical evidence
for a direct or indirect dependency between substorms and storms. A physical
mechanism by which substorms drive storms or vice versa is, therefore,
unlikely.
