The magnetotail dynamics before a substorm Original Research Article

Before a substorm, the magnetotail is reconfigured to accommodate the enhanced solar wind energy input. Pressure build-up in the magnetotail and plasma sheet stretching are typical for substorms with the broad range of magnitudes. Before larger substorms, extra pressure increase can be compensated by plasma heating. Average growth phase duration for small and large isolated substorms differ by only the factor of two, while the solar wind input is different by the order of magnitude. These and other recent findings suggest there is no clear energy or magnetic flux threshold for the substorm initiation, and one rather should look for some time constant of the magnetotail system.