ESA Science & Technology - Auroral substorms triggered by 'short circuiting' of plasma flows

When magnetic reconnection occurs in the magnetotail, it sends hot plasma flows (red) hurtling towards Earth which create the substorms. When the plasma flow impacts the plasmapause – the outer edge of Earth's plasmasphere – the electrons are halted and pile up at the boundary of the plasmasphere, creating turbulence. The ions from the plasma flow continue into the plasmasphere. Waves from the turbulent boundary layer then interact with electrons in the plasma sheet. This creates enhanced precipitation of electrons (the yellow arrow) that causes localized brightening in the auroral oval just before it breaks up into a substorm.