solar cycle 15
{{Infobox Solar cycles
|cycle_num=15
|image=Kraus slunce 1926-01-23.jpg
|caption=Sunspots recorded during solar cycle 15 (23 January 1923).
|start_date=July 1913
|end_date=August 1923
|duration=10.1
|max_count=175.7
|max_count_date=August 1917
|min_count=2.5
|spotless_count=534
|prev_name=Solar cycle 14
|next_name=Solar cycle 16
|prev_dates=1902–1913
|next_dates=1923–1933
}}
Solar cycle 15 was the fifteenth solar cycle since 1755, when extensive recording of solar sunspot activity began.{{citation|doi=10.1023/A:1014296529097|year=2002|last1=Kane|first1=R.P.|title=Some Implications Using the Group Sunspot Number Reconstruction|journal=Solar Physics|volume=205|issue=2|pages=383–401|bibcode=2002SoPh..205..383K|s2cid=118144552}}{{cite web | title=The Sun: Did You Say the Sun Has Spots? | url=http://www.spacetoday.org/SolSys/Sun/Sunspots.html | publisher=Space Today Online | accessdate=12 August 2010}} The solar cycle lasted 10.1 years, beginning in July 1913 and ending in August 1923. The maximum smoothed sunspot number observed during the solar cycle was 175.7 (August 1917), and the starting minimum was 2.5.SIDC Monthly Smoothed Sunspot Number. "[http://sidc.oma.be/sunspot-data/]" During the minimum transit from solar cycle 15 to 16, there were a total of 534 days with no sunspots.Spotless Days. "[http://spaceweather.com/glossary/spotlessdays.htm?PHPSESSID=dli444kmrjgre0rjq6l86fv144]"{{cite web |url=https://science.nasa.gov/headlines/y2008/11jul_solarcycleupdate.htm|archive-url=https://web.archive.org/web/20080714032353/https://science.nasa.gov/headlines/y2008/11jul_solarcycleupdate.htm|url-status=dead|archive-date=14 July 2008|title=What's Wrong with the Sun? (Nothing)|date=11 July 2008|author=Dr. Tony Phillips|publisher=NASA}}Solaemon's Spotless Days Page. "[http://users.telenet.be/j.janssens/Spotless/Spotless.html]"
History
Geomagnetic storms in March 1918, August 1919, October 1919, and March 1920 affected telegraph lines, while a solar flare on 13 May 1921 also affected rail signal and switching equipment, in what was known as the "New York Railroad Storm."{{Cite web|url=http://www.solarstorms.org/SRefStorms.html|title=Space Weather Newspaper Archives|date=28 July 2017}}
=1921=
A major geomagnetic storm during 13–15 May 1921 caused damage in communication systems and aurora displays in much of the eastern United States.{{Cite web|url=http://www.solarstorms.org/SRefStorms.html|title=Space Weather Newspaper Archives|first=Solar|last=Storms|date=28 July 2017|website=www.solarstorms.org}}
In Sweden, the event caused major disruptions to the telephone exchange in Karlstad and in the early morning of May 15, the building burned down.{{Cite web|last=O'Callaghan|first=Jonathan|title=New Studies Warn of Cataclysmic Solar Superstorms|url=https://www.scientificamerican.com/article/new-studies-warn-of-cataclysmic-solar-superstorms/|access-date=2021-11-08|website=Scientific American|date=3 December 2019 |language=en}} Witnesses described the telephone cables going into the building as glowing.
See also
References
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{{Solar cycles}}
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