The extreme solar and geomagnetic storms on 1940 March 20–25

Abstract

In late March 1940, at least five significant solar flares were reported. They likely launched interplanetary coronal mass ejections (ICMEs), and were associated with one of the largest storm sudden commencements (SSCs) since the year 1868, resulting in space weather hazards that today would have significant societal impacts. The initial solar activity is associated with a short geomagnetic storm and a notable SSC. Afterward, the third flare was reported in the eastern solar quadrant (N12 E37-38) at 11:30–12:30 UT on 23 March, with significant magnetic crochets (up to ≈ |80| nT at Eskdalemuir) during 11:07–11:40 UT. On their basis, we estimate the required energy flux of the source flare as X35±1 in soft X-ray class. The resultant ICMEs caused enormous SSCs (up to > 425 nT recorded at Tucson) and allowed us to estimate an extremely inward magnetopause position (estimated magnetopause standoff position ≈ 3.4 RE). The time series of the resultant geomagnetic storm is reconstructed using a Dst estimate, which peaked at 20 UT on 24 March at ≈ −389 nT. Around the storm main phase, the equatorial boundary of the auroral oval extended ≤ 46.3° at invariant latitudes. This sequence also caused a solar proton event and Forbush decrease (≈ 3%). These sequences indicate pileups of multiple ICMEs, which even achieved a record value of inward magnetopause position. Our analyses of this historical pioneer event bring more insights into possible serious space weather hazards and provide a quantitative basis for future analyses and predictions.

The March 1940 Superstorm: Geoelectromagnetic Hazards and Impacts on American Communication and Power Systems

“…From Section 7, we note that the two sudden commencements on 24 March, both of high amplitude, occurred relatively close in time, just 1.82 hr apart. In light of this observation, we hypothesize, as others have before us, that ICME interaction might have been partly responsible for the “violent” ground‐level geomagnetic disturbance realized during the 24 March 1940, storm (e.g., Hayakawa et al., 2022; Lefèvre et al., 2016). Such interaction is known to result in highly geoeffective ICMEs (e.g., Burlaga et al., 1987; Hess & Zhang, 2017; Lugaz et al., 2017; Scolini et al., 2020).…”

“…Recently, Hayakawa et al. (2022) used historical yearbook records and magnetograms from four low‐latitude observatories to construct a Dst time sequence for the March 1940 storm; we use their Dst time sequence, Figure 7b. They estimate that the storm's greatest strength occurred at 15:00–16:00 EST when Dst reached its minimum value of −389 nT; see Figure 7b.…”

“…Important lessons can be learned from the analysis of past magnetic storms (e.g., Boteler, 2019;Hapgood, 2019;Knipp et al, 2021;Lanzerotti, 2017;. In a recent report, Hayakawa et al (2022) summarize the natural phenomena that were the storm of 24 March 1940. Our focus, here, is on the interpretation of ground-level geoelectromagnetic variation brought by the March 1940 storm and the deleterious impact it had on long-line communication-and power-system interference experienced across North America, and, especially, the contiguous United States (CONUS).…”

Geoeffectiveness of interplanetary shocks controlled by impact angles: past research, recent advancements, and future work

“…As theoretically noted by Samsonov (2011), a very strong solar wind v y component greatly increases the solar wind ram pressure in the y direction, leading to the strong dawn-dusk asymmetry noted in ground magnetic field observed and simulated by Samsonov et al (2015). Historical observations of very intense sudden impulses on the ground suggest that such response was caused by impacts of very fast and nearly frontal shocks on the Earth's magnetosphere (Araki, 2014;Oliveira and Ngwira, 2017;Love et al, 2019a;Love et al, 2019b;Hayakawa et al, 2020a;Hayakawa et al, 2020b;Hayakawa et al, 2021a;Hayakawa et al, 2021b).…”

On the Magnetosphere‐Ionosphere Coupling During the May 2021 Geomagnetic Storm

“…These ORB losses in the relativistic range may be consistent with magnetopause shadowing (Herrera Forbush decreases (FDs) refer to sudden suppression of the short-term galactic cosmic-ray (GCR) intensity (Forbush, 1937;Hess & Demmelmair, 1937), either associated with corotating high-speed streams ("recurrent" FDs) or caused by transient solar wind structures following coronal mass ejections from the Sun ("non-recurrent" FDs). Most of the early observations of such phenomena were carried out by ground-based detectors, such as Neutron Monitors and Muon Telescopes (Cane, 2000;Papailiou et al, 2020;Vieira et al, 2012), and by measurements with ionization chambers (Hayakawa, Oliveira, et al, 2021) allowing only for an indirect detection of the neutrons generated in the atmosphere. Figure 7 shows the variation of GCR protons measured by the HEPD-01 instrument, directly from space, across the storm and post-storm of May 2021.…”