The Causes and Effects of the Carrington Event

From 1 September 1859 to 2 September 1859, Earth experienced the largest geomagnetic storm on record. There were sightings of visible auroras reaching to 18◦ latitude and the telegraph system was shut down due to changes in the geomagnetic field. Richard Carrington, the storm’s namesake, recorded observations of a bright light flash on the sun hours before the onset of magnetic disturbances. The combination of Carrington’s observations, the bright widespread auroras, and the disruption of the telegraphs lead scientists to determine the link between these phenomena. Since then scientists have made discoveries allowing them to understand solar activity, the interaction between the geomagnetic field and the interplanetary magnetic field, and geomagnetic storms. This manuscript details modern understandings of the events leading up to the Carrington Event and their effects on Earth. To begin, it describes the formation and interplanetary travel of the coronal mass ejection that caused the storm. It then discusses how the magnetic fields interact and cause changes in the strength and location of Birkeland currents. Next, it describes the effects seen on Earth, including the formation of visible auroras and how the telegraph system became inoperable. Finally, using this historic event it sets the foundation for understanding how Earth would be affected by a similar geomagnetic storm today