Free Astronomy Magazine July-August 2024

9 JULY-AUGUST 2024 1 st CME traveled so fast. Researchers believe a smaller CME erupted from the Sun in late August and cleared the path between the Sun and the Earth of most of the solar wind plasma that would normally slow a CME. When the September 1st event observed by Carrington and Hodg- son began, conditions were there- fore perfect for the massive storm to pass through the inner solar system and crash into Earth’s magnetos- phere in just a matter of hours. A similar sequence, fortunately on a smaller scale, occurred just last May following a series of solar flares in the active solar region 3664. Leaving aside the purely spectacular aspect of the auroras, we want to focus here on the consequences that the massive geomagnetic distur- bance had on the technologies of 1859. The main victims were the tele- graph lines, an invention patented fifteen years earlier, that were be- coming increasingly widespread in the “civilized world.” There are his- torical testimonials in Europe, North America, and Australia that tell of sparks coming from the wires that carried the signals−sparks that, in some cases, caused small fires. Other testimonials refer to electric shocks T rend of geomagnetic activity in the period centered on the Carrington Event, recorded at the Greenwich Royal Observatory, Lon- don, from August 27 to September 7, 1859. The declination, or compass direction, (D) is the lower trace on each image, and the horizontal force (H) is the upper trace. Hours in Universal Time, plus 12 hours, and the measured D precedes the H by approximately 12 hours. The CME that arrived on August 28 was the one that swept interplanetary space, allowing the much more massive one that arrived on Sep- tember 2 to impact the magnetos- phere with extreme violence. [British Geological Survey]