Are we ready for a repeat of the 1859 Carrington-Hodgson Solar Superstorm Event?
- CERES team
- 14 minutes ago
- 4 min read
FOR IMMEDIATE RELEASE
May 2024 Solar Superstorm Confirmed as Strongest Flare Event in 87-Year Record
New Hemispheric Solar Flare Index Provides Critical Space Weather Data for Protecting Modern Infrastructure
MEXICO CITY (November 13, 2025):
This week, the world saw yet another display of spectacular aurorae (November 11-12, 2025) at latitudes as low as El Salvador and Mexico. This was a year after similar unusually low-latitude aurorae events that captivated millions worldwide in May 2024.
Coincidentally, groundbreaking research published today in Space Weather reveals that the 2024 aurorae resulted from the most intense solar flare ever recorded in nearly nine decades of observations. An international team of solar physicists has unveiled the most comprehensive record of solar flare activity ever compiled, spanning 1937 to 2024, and revealing critical patterns that could help predict future space weather threats.
2024's Storm was a Historic Solar Event
On May 6, 2024, the Sun's northern hemisphere produced a solar flare with a Solar Flare Index (SFI) value of 173.5. This was the highest recorded since systematic monitoring began in 1937. This event started a major solar storm, known as the “Gannon Storm” or the “Mother’s Day storm”. This led to a major geomagnetic storm on Earth a few days later that produced aurorae visible as far south as 23 degrees magnetic latitude and also caused other significant disturbances.
“This represents the most powerful solar flare activity in our instrumental record,” said lead author Dr. Víctor M. Velasco Herrera of Universidad Nacional Autónoma de México. “The May 2024 events remind us that extreme space weather events are a clear and present danger to our technology-dependent civilization.”
An Important New Dataset for Space Weather
The research introduces the hemispheric Solar Flare Index (hSFI), which separately tracks flare activity in the Sun's northern and southern hemispheres. This innovative approach, combining data from observatories in the Czech Republic (1937-1976, formerly Czechoslovakia) and Turkey (1977-2024), reveals patterns invisible when examining only the full solar disc.
The analysis shows the northern hemisphere dominated solar flare activity from Solar Cycles 17 through 21 (1937 to March 1986), but the southern hemisphere has dominated since Solar Cycle 22 (April 1986 till now 2025). This makes the May 2024 northern hemisphere record-breaker particularly noteworthy.
“By resolving solar activity hemispherically, we discovered a remarkable pattern: the Sun’s two hemispheres take turns dominating flare production over multi-decadal periods,” explained co-author, Dr. Willie Soon, of the Center for Environmental Research and Earth Sciences (CERES).
Are we ready for a repeat of the 1859 Carrington-Hodgson Event?
The May 2024 geomagnetic storm reached a minimum daily Dxt index of -293.40 nT, the strongest daily average since 1937, and triggered Ground Level Event #74, where solar energetic particles penetrated to Earth's surface – a relatively rare and dangerous phenomenon.
However, while the May 2024 storm is the most extreme on the instrumental record, it is known that more extreme events have occurred in the past – and likely will occur in the future. In particular, the famous 1859 Carrington-Hodgson Event was so extreme that it majorly disrupted the telegraph system worldwide. But, 1859 was decades before electrical grids had been set up and a century before the satellite era began in 1957. Furthermore, the research team cautions that analysis of sun-like stars and proxy records suggests Earth could expect solar flares even larger than the 1859 Carrington-Hodgson Event in the future.
The May 2024 storm is the closest we have gotten to another Carrington-Hodgson Event and it is a stark reminder that the possibility of comparable events in the near future threaten modern infrastructure including power grids, GPS systems, communications networks, and satellites.
“Historical evidence suggests the 1859 Carrington-Hodgson Event was even more powerful than what we experienced in May 2024,” Dr. Velasco Herrera noted. “Society must prepare for the possibility of even larger solar storms that could cause widespread technological disruption.”
Using Machine Learning for Predictive Power
The research uncovered several patterns with forecasting potential. Most significantly, a 1.7-year periodicity in solar activity appears to strongly influence when major geomagnetic storms occur. The analysis shows that 90% of extreme geomagnetic storms occurred during the positive phase of this cycle.
Additionally, the team identified a 30-year pattern correlating with low-latitude auroral events. Although the study only covers the period up to 2024, the authors had correctly anticipated from this model that low latitude aurorae such as those of this week were possible since we are still experiencing the solar maximum of Solar Cycle 25. This model predicts that after the current Solar Cycle 25 ends, the next elevated risk period may occur during Solar Cycles 27 and 28 in the 2040s-2050s.
The study also confirms the “Gnevyshev-Ohl rule” applies to solar flares: odd-numbered solar cycles consistently produce more total flare energy than subsequent even-numbered cycles.
International Collaboration
Creating the dataset required extensive international cooperation, with four independent researchers verifying historical records and continuous monitoring spanning 87 years across two observatories. The research was conducted by an international team from institutions in Mexico, Hungary, the United States, Turkey, the Czech Republic, Slovakia, China, Ireland, Russia, and Argentina.
The complete dataset is available in daily, monthly, and annual resolutions through the Harvard Dataverse repository (links below).
As Solar Cycle 25 continues its ongoing maximum activity, this new dataset will provide crucial context for understanding ongoing solar activity and its potential impacts on our increasingly interconnected technological civilization.
Further details
Link to the study:
V. M. Velasco Herrera, W. Soon, S. Knoška, A. Özgüç, G. Velasco Herrera, H. Yeşilyaprak, N. Babynets, M. Švanda, J. Muraközy, S. Qiu, D. Riveros-Rosas, R. Connolly, M. Connolly, A. Tlatov, L. Cappellotto (2025). "Solar flare activity, 1937–2024: Introducing the new hemispheric Solar Flare Index (hSFI) in the context of 2024's major solar storm events." Space Weather, 23, e2025SW004515. https://doi.org/10.1029/2025SW004515.
Links to the dataset:
Velasco Herrera, V. (2025). Solar flare activity, 1937‐2024: Introducing the new hemispheric solar flare index (hsfi) in the context of 2024’s major solar storm events. Harvard Dataverse:
1) Total solar flare index (SFI): https://doi.org/10.7910/DVN/9TILW5
2) Northern hemisphere index (nhSFI). https://doi.org/10.7910/DVN/TSQEPB
3) Southern hemisphere index (shSFI). https://doi.org/10.7910/DVN/C1L8ZX
Contact:
Dr. Víctor M. Velasco Herrera, Instituto de Geofísica, Universidad Nacional Autónoma de México; Email: vmv@igeofisica.unam.mx
Video summary
Co-author, Dr. Ronan Connolly, has posted a video summary of the paper on his YouTube channel below: