Recent missions of the THEMIS satellite fleet have revealed a new form of space weather caused by plasma jets coming from Earths magnetic tail. These tremors in Earths magentic field--or "spacequakes"--are triggered by solar winds stretching the planets magnetic field and trapping plasma in the Earths magnetic tail. When the tail snaps from the tension, it sends plasma jets into the geomagnetic field that then rebound and bounce, dissipating the energy against the magnetic field. NASA researchers were surprised to discover plasma vortices, huge whirls of magnetized gas as wide as the Earth itself, forming around the plasma jets as they hit the magnetosphere. Studies suggest that the tails may funnel particles into Earths atmosphere that spark arouras and make waves of ionization that disturb radio communications and GPS and cause potentially lethal ground fault currents.
The plasma vortices that cause it all can be seen from Earth in the form of ripples and swirls in auroral displays, but research continues into how big spacequakes and vortices can get, and how they interact with each other.
image: "Sunspot and Its Magnetic Field (NASA, Hinode, 2007)" by NASA's Marshall Space Flight Center on FLickr via Creative Commons licensing.