Energetics of Shock-triggered Supersubstorms (SML <-2500 nT)

The solar wind energy input and dissipation in the magnetospheric-ionospheric systems of 17 supersubstorms (SSSs: SML < -2500 nT) triggered by interplanetary shocks during solar cycles 23 and 24 are studied in detail. The SSS events had durations ranging from similar to 42 minutes to similar to 6 hr, and SML intensities ranging from -2522 nT to -4143 nT. Shock compression greatly strengthens the upstream interplanetary magnetic field southward component (B (s)), and thus, through magnetic reconnection at the Earth's dayside magnetopause, greatly enhances the solar wind energy input into the magnetosphere and ionosphere during the SSS events studied. The additional solar wind magnetic reconnection energy input supplements the similar to 1.5 hr precursor (growth-phase) energy input and both supply the necessary energy for the high-intensity, long-duration SSS events. Some of the solar wind energy is immediately deposited in the magnetosphere/ionosphere system, and some is stored in the magnetosphere/magnetotail system. During the SSS events, the major part of the solar wind input energy is dissipated into Joule heating (similar to 30%), with substantially less energy dissipation in auroral precipitation (similar to 3%) and ring current energy (similar to 2%). The remainder of the solar wind energy input is probably lost down the magnetotail. It is found that during the SSS events, the dayside Joule heating is comparable to that of the nightside Joule heating, giving a picture of the global energy dissipation in the magnetospheric/ionospheric system, not simply a nightside-sector substorm effect. Several cases are shown where an SSS is the only substorm that occurs during a magnetic storm, essentially equating the two phenomena for these cases.

Automated summary

This study examines the input and dissipation of solar wind energy in the magnetospheric-ionospheric systems during 17 supersubstorms triggered by interplanetary shocks. The research finds that shock compression significantly increases the southward component of the interplanetary magnetic field, leading to enhanced solar wind energy input through magnetic reconnection. This additional energy supplements the precursor energy input, resulting in high-intensity, long-duration supersubstorms.