Common solar wind drivers behind magnetic storm-magnetospheric substorm dependency

TL;DR

This study uses causal inference to identify the interplanetary magnetic field as the main driver behind both magnetic storms and substorms, challenging the idea of a direct dependency between them.

Contribution

It demonstrates that the vertical component of the interplanetary magnetic field is the common driver for storms and substorms, providing new insights into their relationship.

Findings

The vertical component of the interplanetary magnetic field drives both storms and substorms.

No statistical evidence supports a direct or indirect dependency between storms and substorms.

Results are consistent across solar maximum and minimum phases.

Abstract

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.