The Impact of the May 1921 Superstorm on American Telecommunication Systems

Love, Jeffrey J. ORCID: https://orcid.org/0000-0002-3324-0348; Lucas, Greg M. ORCID: https://orcid.org/0000-0003-1331-1863; Kelbert, Anna ORCID: https://orcid.org/0000-0003-4395-398X; Schnepf, Neesha R. ORCID: https://orcid.org/0000-0003-1489-7958; Bedrosian, Paul A. ORCID: https://orcid.org/0000-0002-6786-1038; McBride, Sara K.; Oughton, Edward J. ORCID: https://orcid.org/0000-0002-2766-008X. 2025 The Impact of the May 1921 Superstorm on American Telecommunication Systems. Space Weather, 23 (7), e2025SW004563. 7, pp. 10.1029/2025SW004563

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Official URL: https://doi.org/10.1029/2025SW004563

Abstract/Summary

A compilation is presented of impacts (interference and damage) realized on long-line telegraph and telephone systems across North America during the 13–16 May 1921 magnetic storm. Impacts occurred primarily during local nighttime, after the third of four sudden commencements, and during the storm's most-prominent main phase. Impacts are attributed to rapid and high-amplitude geomagnetic field variation generated by substorms. This induced potential differences and between the grounding points of communication networks that were sufficient to cause system interference and damage. In the United States, impacts were concentrated in the Midwest and in the East, regions characterized by high electromagnetic surface impedance. Given technological changes, modern telecommunication systems are less exposed to storms like that of May 1921, while power-grid systems are now more exposed to them.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2025SW004563
ISSN:	1542-7390
Additional Keywords:	extreme event, geomagnetically induced current, hazard analysis, historical event, magnetic storm.
Date made live:	31 Jul 2025 15:02 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539981

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1029/2025SW004563

ISSN:

1542-7390

Additional Keywords:

extreme event, geomagnetically induced current, hazard analysis, historical event, magnetic storm.

Date made live:

31 Jul 2025 15:02 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/539981