Intensity and Impact of the New York Railroad Superstorm of May 1921

Abstract

Analysis is made of low-latitude ground-based magnetometer data recording the magnetic superstorm of May 1921. By inference, the storm was driven by a series of interplanetary coronal mass ejections, one of which produced a maximum pressure on the magnetopause of~64.5 nPa, sufficient to compress the subsolar magnetopause radius to~5.3 Earth radii. Over the course of the storm, low-latitude geomagnetic disturbance exhibited extreme local time (longitude) asymmetry that can be attributed to substorm disturbance extending to low latitudes. The storm attained an estimated maximum −Dst on 15 May of 907 ± 132 nT, an intensity comparable to that of the Carrington event of 1859. The May 1921 storm brought spectacular aurorae to the nighttime sky. It also interfered with and damaged telephone and telegraph systems associated with railroad systems in New York City and State. These later effects were due to a combination of three factors: the localized details of geomagnetic vector disturbance, the geographic expression of the Earth's surface impedance tensor, and the configurations and physical parameters of the electrical networks of the day.Plain Language Summary Historical records of ground-level geomagnetic disturbance are analyzed for the magnetic superstorm of May 1921. This storm was almost certainly driven by a series of interplanetary coronal mass ejections of plasma from an active region on the Sun. The May 1921 storm was one of the most intense ever recorded by ground-level magnetometers. It exhibited violent levels of geomagnetic disturbance, caused widespread interference to telephone and telegraph systems in New York City and State, and brought spectacular aurorae to the nighttime sky. Results inform modern projects for assessing and mitigating the effects of magnetic storms that might occur in the future.

Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms Around the Carrington Event in 1859

“…Dietrich, 2013; Siscoe et al, 2006), whereas the maximal amplitude of horizontal force at Bombay was reported 1760 nT (Tsurutani et al, 2003). This hourly value is comparable to that of the May 1921 storm (see Love et al, 2019b). This comparison tells us that the Carrington event was not likely unique but one of the most extreme events.…”

“…These reports make it possible to estimate that the equatorward boundary of the auroral oval in the Eastern Hemisphere extended at least beyond the overhead positions of the Russian stations (≈37°M LAT), even during the recovery phase of the Carrington storms, after the extreme negative excursion recorded at Bombay. The conservative estimate of the equatorward boundary of auroral oval in the (Rich & Denig, 1992), S+06 (Siscoe et al, 2006), H+18a (Hayakawa, Ebihara, Willis, et al, 2018), H+18b (Hayakawa, Ebihara, Hand, et al, 2018), H+19a (Hayakawa, Ebihara, et al, 2019), L+19a (Love et al, 2019a), and L+19b (Love et al, 2019b) Note. The equatorward boundary of the auroral oval for the Hydro-Quebec Event is based on auroral particle precipitation and the auroral electric field.…”

“…Regarding the extreme magnetic storm on 14/15 May 1921 (Hapgood, ; Silverman & Cliver, ), the aurora was reported down to Apia with a significant magnetic disturbance (Angenheister & Westland, , p. 202). The Dst value is computed to be ≈−907 ± 132 nT, on the basis of magnetograms at Apia, Vassouras, San Fernando, and Watheroo (Love et al, ). The MLAT of Apia is computed as −16.2° MLAT based on the authorized International Geomagnetic Reference Field dipole model (see Thébault et al, ).…”

A 21st Century View of the March 1989 Magnetic Storm

“…By any measure the storm was large: The magnetic index Kp reached 9+, the top of its scale, and the Dst value of −589 nT was the largest since the Dst index started in 1957. (Estimated Dst values of −850 to −1,760 nT for the 1859 Carrington storm and estimated Dst value of −907 nT for the May 1921 storm place these events as the largest in modern times; Siscoe et al, ; Tsurutani et al, ; Hayakawa et al, ; Love et al, .) However, the index numbers do not tell the whole story.…”

Some Experiments in Extreme‐Value Statistical Modeling of Magnetic Superstorm Intensities

“…LOVE MAGNETIC SUPERSTORM STATISTICS 5 of 22 10.1029/2019SW002255 (Bezdek & Solomon, 1983;Mugele & Evans, 1951). We note that Vasyliūnas's upper limit on −Dst m is far higher than that which occurred for the March 1989 storm, far higher than that realized for the storm of May 1921 −Dst m = 907 nT (Love et al, 2019b), and far higher than for the Carrington event of 1859, approximately 850 nT (Siscoe et al, 2006) to 1,050 nT .…”