science

May 1921 geomagnetic storm

May 1921 geomagnetic storm is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand May 1921 geomagnetic storm rather than just read about it. In short: The three-day May 1921 geomagnetic storm, also known as the New York Railroad Storm, was caused by the impact of an extraordinarily powerful coronal mass ejection on Earth's magnetosphere. It occurred on 13–15 May as part of solar cycle 15, and was the most intense geomagnetic storm of the 20th century.

Key takeaways

May 1921 geomagnetic storm belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect May 1921 geomagnetic storm to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of May 1921 geomagnetic storm from memory before moving on to harder problems.

Reference excerpt

The three-day May 1921 geomagnetic storm, also known as the New York Railroad Storm, was caused by the impact of an extraordinarily powerful coronal mass ejection on Earth's magnetosphere. It occurred on 13–15 May as part of solar cycle 15, and was the most intense geomagnetic storm of the 20th century. Since it occurred before the extensive interconnectivity of electrical systems and the general electrical dependence of infrastructure in the developed world, its effect was restricted; however, its ground currents were up to an order of magnitude greater than those of the March 1989 geomagnetic storm which interrupted electrical service to large parts of northeastern North America.

Effects The storm's electrical current sparked a number of fires worldwide, including one near Grand Central Terminal which made it known as the "New York Railroad Storm". Contemporary scientists estimated the size of the sunspot (AR1842) which began on May 10—and caused the storm—as 151,000 by 34,000 km (94,000 by 21,000 miles). The storm was extensively reported in New York City, which was a center of telegraph activity as a railroad hub. Auroras ("northern lights") appeared throughout the eastern United States, creating brightly lit night skies. Telegraph service in the U.S. first slowed and then virtually stopped at about midnight on 14 May due to blown fuses and damaged equipment. Radio propagation was enhanced during the storm due to ionosphere involvement, however, enabling unusually good long-distance reception. Electric lights were not noticeably affected. Undersea telegraph cables were affected by the storm. Damage to telegraph systems was also reported in Europe and the Southern Hemisphere.

Comparison to other geomagnetic storms In space weather, the disturbance storm time index (Dst index) is a measure often used for determining the intensity of solar storms. A negative Dst index means that Earth's magnetic field is weakened—particularly the case during solar storms—with a more negative Dst index indicating a stronger solar storm. A paper in 2019 estimated that the May 1921 geomagnetic storm had a peak Dst of −907±132 nT. For comparison, the Carrington Event of 1859 had a peak Dst estimated to be between −800 nT and −1750 nT. The March 1989 geomagnetic storm had a peak Dst index of −589 nT.

See also Active region Geomagnetic storm List of solar storms

References

Footnotes

Bibliography The Aurora Borealis of May 14, 1921 JSTOR 40710695 "May 13, 1921 – The New York Railroad Storm". Solarstorms.org. Retrieved February 9, 2019. A bibliography of newspaper and journal articles. "Northern Lights Are Busy" (PDF). New York Times. May 14, 1921. p. 10. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. "Aurora Borealis Halts Telegraph Service to City" (PDF). The Atlanta Constitution. May 15, 1921. p. 1. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. Henry K. Bunn (May 15, 1921). "The Story The Week Has Told" (PDF). The Atlanta Constitution. p. 8. Archived from the original (PDF) on March 4, 2016. Retrieved December 19, 2012. "Tricky Aurora Snarls Up Wires" (PDF). Chicago Daily Tribune. May 15, 1921. p. 1. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. "Aurora is Disturber" (PDF). The Los Angeles Times. May 15, 1921. pp. 1 & 2. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. "The Aurora Borealis" (PDF). The Los Angeles Times. May 16, 1921. p. 14. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. "Aurora Borealis Effect on Wires Laid to Sun Spot" (PDF). The Atlanta Constitution. May 16, 1921. p. 3. Archived from the original (PDF) on March 3, 2016. Retrieved December 19, 2012. "Sunspot Credited with Rail Tie-Up" (PDF). New York Times. May 16, 1921. p. 2. Archived from the original (PDF) on March 4, 2016. Retrieved December 19, 2012. "Magnetic Tremors Expected to Pass Within 48 Hours" (PDF). New York Times. May 16, 1921. p. 1. Archived from the original (PDF) on March 4, 2016. Retrieved December 19, 2012. "Cables Still Show Effects of Aurora" (PDF). New York Times. May 18, 1921. p. 12. Archived from the original (PDF) on March 3, 2016. 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. Archived from the original (PDF) on March 4, 2016. 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.

Illustrations

Worked examples

Example 1 — a first encounter with May 1921 geomagnetic storm

Start with the simplest possible case. Write down what May 1921 geomagnetic storm claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to May 1921 geomagnetic storm before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about May 1921 geomagnetic storm ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of May 1921 geomagnetic storm

In research: May 1921 geomagnetic storm appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses May 1921 geomagnetic storm in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: May 1921 geomagnetic storm is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1921 in science, 1921 natural disasters, 1921 natural disasters in the United States, so understanding it makes those chapters shorter.
In everyday life: Look for May 1921 geomagnetic storm outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study May 1921 geomagnetic storm in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what May 1921 geomagnetic storm means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain May 1921 geomagnetic storm out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is May 1921 geomagnetic storm in simple terms?

Why does May 1921 geomagnetic storm matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study May 1921 geomagnetic storm?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on May 1921 geomagnetic storm.