The bursts were distinguished by the way the frequency drifted with time. The team deduced that the type II bursts were associated with shock waves coming out through the solar atmosphere at 1000 km/s and were associated, 30 hours later, with aurora in the Earth's night sky. They had discovered the answer to a century-old riddle: what was the agency that conveyed the disturbance from the solar flare to the Earth? Type II bursts continue to be closely monitored by spectrographs on the ground and in satellites for "space weather" reporting, since their disruption of the geomagnetic field and ionosphere can cause blackouts to radio communication and the systems of navigational and other satellites.