May 1921 geomagnetic storm

The May 1921 geomagnetic storm was a significant event caused by the impact of an extraordinarily powerful coronal mass ejection on Earth's magnetosphere. It took place on 13 through 15 May, and was part of solar cycle 15. This event occurred before extensive interconnectivity of electrical systems and the general electrical dependency across infrastructures in the developed world, so the effect was restricted to certain sectors, even though resulting ground currents were up to an order of magnitude greater than those of the March 1989 geomagnetic storm that blacked out large parts of northeastern North America.^[1] At the time, scientists gave the size of the sunspot that began on May 10th and caused the storm as 94,000 by 21,000 miles (131,000 km by 33,800 km) in size.^[2][3]

Northern lights appeared in much of the eastern United States, creating brightly lit night skies. Telegraph service in the United States was slowed and then virtually eliminated around midnight of the 14th due to blown fuses, and damaged equipment. On the other hand, radio waves were strengthened during the storm due to ionosphere activation, allowing for some strong intercontinental reception. Electric lights did not seem to have been noticeably affected.^[4] Undersea cables also suffered from the storm. Damage to telegraph systems were also reported in Europe ^[5] and the southern hemisphere.^[6]

See also

• List of solar storms

References

Footnotes

1. Dr Tony Phillips (January 21, 2009). "Severe Space Weather - Social and Economic Impacts". NASA. Retrieved December 18, 2012.
2. "Borealis Cause, Sun Spots, Will Diminish Today" (PDF). Chicago Daily Tribune. May 16, 1921. p. 4. Retrieved December 19, 2012.
3. "Sun Spots Vanishing" (PDF). The Los Angeles Times. May 16, 1921. pp. 1 & 2. Retrieved December 19, 2012.
4. "Sunspot Aurora Paralyses Wires" (PDF). New York Times. May 15, 1921. pp. 1 & 3. Retrieved December 19, 2012.
5. "Cables Damaged by Sunspot Aurora" (PDF). New York Times. May 17, 1921. pp. 1 & 4. Retrieved December 19, 2012.
6. "Aurora Borealis". Hawera & Normanby Star. May 16, 1921. p. 8. Retrieved December 18, 2012.

Bibliography

• JSTOR 40710695
• "Solar Storm and Aurora of May 13, 1921". Solarstorms.org. Retrieved December 18, 2012.
• "Northern Lights Are Busy" (PDF). New York Times. May 14, 1921. p. 10. Retrieved December 19, 2012.
• "Aurora Borealis Halts Telegraph Service to City" (PDF). The Atlanta Constitution. May 15, 1921. p. 1. Retrieved December 19, 2012.
• Henry K. Bunn (May 15, 1921). "The Story The Week Has Told" (PDF). The Atlanta Constitution. p. 8. Retrieved December 19, 2012.
• "Tricky Aurora Snarls Up Wires" (PDF). Chicago Daily Tribune. May 15, 1921. p. 1. Retrieved December 19, 2012.
• "Aurora is Disturber" (PDF). The Los Angeles Times. May 15, 1921. pp. 1 & 2. Retrieved December 19, 2012.
• "The Aurora Borealis" (PDF). The Los Angeles Times. May 16, 1921. p. 14. Retrieved December 19, 2012.
• "Aurora Borealis Effect on Wires Laid to Sun Spot" (PDF). The Atlanta Constitution. May 16, 1921. p. 3. Retrieved December 19, 2012.
• "Sunspot Credited with Rail Tie-Up" (PDF). New York Times. May 16, 1921. p. 2. Retrieved December 19, 2012.
• "Magnetic Tremors Expected to Pass Within 48 Hours" (PDF). New York Times. May 16, 1921. p. 1. Retrieved December 19, 2012.
• "Cables Still Show Effects of Aurora" (PDF). New York Times. May 18, 1921. p. 12. Retrieved December 19, 2012.
• "Electric Disturbances Affect French Wires: Aurora Not Visible, Its Absence Being Attributed to Atmospheric Conditions" (PDF). New York Times. May 18, 1921. p. 12. Retrieved December 19, 2012.
• "Magnetic Storms Don't Affect Radio" (PDF). New York Times. May 26, 1921. p. 23. Retrieved December 19, 2012.
• S.M. Silverman; E.W.Cliver (March 2001). "Low-latitude auroras: the magnetic storm of 14–15 May 1921". Journal of Atmospheric and Solar-Terrestrial Physics 63 (5): 523–525. Bibcode:2001JASTP..63..523S. doi:10.1016/S1364-6826(00)00174-7. Retrieved December 18, 2012.