Study of the Dst-AL correlation during geospace magnetic storms

A dispute on the role of substorms in geospace magnetic storm development has emerged during the last decade; the scientific community has not yet reached a definite conclusion. This paper attempts to clarify, to the extent possible with statistical methods, if there is any causal relationship between the energy dissipation during storms and during substorms. To assess this aspect of the storm-substorm relationship, we performed an investigation using the geomagnetic indexes SYM-H and AL for a large number of magnetic storms. We selected a group of 53 magnetic storms with SYM-H peak values in the range between -50 nT and -350 nT. We then calculated the integrals of the SYM-H and AL squares, to represent magnetic energy dissipation for storms and substorms respectively. These integrals exhibit a strong linear correlation, with a correlation index of r=0.928. The result implies a strong coupling between storm and substorm energy dissipation.