2016-09-15. The Geomagnetic Blitz of September 1941.

posted Sep 17, 2016, 9:38 AM by Alan Gould   [ updated Sep 17, 2016, 9:40 AM ]
By Jeffrey J. Love and Pierdavide Coïsson, for Earth and Space News EOS (AGU). For GSS Energy Flow chapter 4. Excerpt: Seventy-five years ago next week, a massive geomagnetic storm disrupted electrical power, interrupted radio broadcasts, and illuminated the night sky in a World War II battle theater. ...Auroras danced across the night sky as voltage surged in power grid lines. A radio blackout interrupted fan enjoyment of a baseball game, while another radio program was interrupted by private phone conversations. ...And far away in the North Atlantic, the illuminated night sky exposed an Allied convoy to German attack. ...On the basis of daily sunspot reports supplied by the U.S. Naval Observatory, the Department of Terrestrial Magnetism at the Carnegie Institution of Washington formally issued a warning to radio operators that they could expect significant disturbances to ionospheric and geomagnetic conditions beginning on about 18 September.... This prediction, which turned out to be accurate, is a noteworthy development in the historical development of methods for reliably forecasting space weather. Less than 20 hours after the flare was reported by Greenwich, a magnetic storm commenced at 0412 UT on 18 September with the arrival at Earth of a coronal mass ejection. ...On 18–19 September 1941, the Moon was nearly new, ideal for seeing the auroral light.... The observer in charge at the Cheltenham, Md., observatory reported a brilliant auroral display of rays and moving drapery of pink, green, and lavender. He also described an auroral corona, where light appears to stream down from directly overhead, a phenomenon rarely seen at midcontinental latitudes. ...Weather Service observers reported seeing auroras in New Mexico [Cameron, 1941]. ...at 19:45 and 19:50 UT, the Pennsylvania Water and Power Company recorded uncontrolled voltage variations in transmission lines connecting generating plants on the Susquehanna River with Baltimore and Washington. At the moment when the auroral brilliance was greatest, system transformers vibrated and groaned as a result of geomagnetically induced currents....  https://eos.org/features/the-geomagnetic-blitz-of-september-1941  See also  Scientists Get First Glimpse of Solar Wind as It Forms.