A solar storm on the scale of the 1859 Carrington Event would not burn cities to the ground, but it would hit modern civilization where it hurts most: the electrical grid, satellite networks, GPS navigation, and the financial systems that depend on all three. The original event disrupted about 200,000 kilometers of telegraph lines for eight hours or more, and telegraph operators in Boston famously sent messages using nothing but the electrical current the storm induced in their wires.1PubMed Central. Duration and extent of the great auroral storm of 1859 Today, the wires are longer, the systems are more interconnected, and the stakes are incomparably higher.
How Big Was the Carrington Event, Really
The Carrington Event is the benchmark for “worst-case solar storm,” but even among researchers, the intensity is still debated. The storm’s strength is measured by how much it disturbed Earth’s magnetic field, recorded at the time by a single magnetometer in Colaba, India. Depending on how that record is interpreted, the estimated peak disturbance falls somewhere around 850 to 960 nT, with uncertainty stretching from the mid-700s to above 1,000 nT.2Journal of Space Weather and Space Climate. On the uncertain intensity estimate of the 1859 Carrington storm For comparison, the March 1989 storm that knocked out power across Quebec registered about 590 nT. The Carrington Event was roughly 50 to 70 percent stronger than that, possibly more.
Two distinct phases hit during the original event. A first magnetic disturbance on the evening of August 28 disrupted telegraph operations across Europe, and a second, far more powerful pulse arrived on September 2, hammering North American telegraph lines during business hours.3Advances in Space Research. The super storms of August/September 1859 and their effects on the telegraph system That two-phase pattern matters because it suggests a modern repeat could involve multiple waves of disruption, complicating response efforts.
The Power Grid Is the Central Vulnerability
The most consequential impact of a modern Carrington-scale storm would be on electrical power systems. When a coronal mass ejection slams into Earth’s magnetic field, it generates geomagnetically induced currents (GICs) that flow through any long conductor in contact with the ground. Power transmission lines, which span hundreds or thousands of kilometers, are ideal conductors for these currents. When GICs enter a high-voltage transformer, they partially saturate its magnetic core, causing overheating, harmonic distortion in the electrical waveform, and potential misoperation of protective relays.4Journal of Applied Research and Technology. Core saturation effects of geomagnetic induced currents in power transformers In practical terms, this means transformers can be permanently damaged, voltage can become unstable across wide regions, and the protective systems designed to prevent cascading failures can themselves malfunction.
We have a real-world example of how this plays out at much lower storm intensities. The 1989 geomagnetic storm caused a blackout across Hydro-Québec’s entire grid in about 90 seconds. Analysis of that event found that the substorm responsible may have been externally triggered by a sudden compression of Earth’s magnetosphere, which sped up the onset and produced larger GICs than a purely internal substorm would have.5Space Weather. A 21st Century View of the March 1989 Magnetic Storm A Carrington-scale event would produce GICs many times larger and over a much wider area, potentially affecting grids across entire continents simultaneously.
The real danger is not just a blackout but a blackout you cannot easily reverse. Large high-voltage transformers are custom-built, weigh hundreds of tons, and have manufacturing lead times measured in months to over a year. If a superstorm damaged dozens or hundreds of them across a national grid, restoring full power could take not days or weeks but potentially months. Every system that depends on electricity, which in 2025 is essentially every system, would be affected downstream.
Satellites Caught in the Blast
The space around Earth would become an extremely hostile environment during a Carrington-class event. Modeling of extreme coronal mass ejections suggests that the interplanetary shock could arrive at Earth within roughly 12 hours, compressing the magnetopause inward to about four Earth radii from the surface. At that distance, satellites in geosynchronous orbit (about 6.6 Earth radii) and many in medium Earth orbit would find themselves outside the protective magnetosphere entirely, directly exposed to high-energy particle radiation from the flare and the shock wave.6Geophysical Research Letters. An extreme coronal mass ejection and consequences for the magnetosphere and Earth The resulting radiation levels could degrade solar panels, corrupt onboard electronics, and in some cases render satellites permanently inoperable.
Satellites in low Earth orbit face a different but equally serious threat. The storm heats and expands Earth’s upper atmosphere, dramatically increasing aerodynamic drag on anything orbiting within it. Research on historical superstorms shows that orbital decay is driven not just by peak storm intensity but by how long the storm lasts, and long-duration superstorms can be far more destructive to satellite orbits than short but intense bursts.7Space Weather. Estimating Satellite Orbital Drag During Historical Magnetic Superstorms A storm lasting a day or more could cause satellites to drop significantly in altitude, potentially leading to uncontrolled reentry or collision with other objects. SpaceX learned a mild version of this lesson in February 2022 when a moderate geomagnetic storm caused 38 newly launched Starlink satellites to reenter the atmosphere before they could reach their operational orbits. Scale that up to a Carrington-level event, and the losses among thousands of active satellites could be substantial.
GPS Errors Measured in Tens of Meters
Geomagnetic storms wreak havoc on the ionosphere, the electrically charged layer of the atmosphere that GPS signals must pass through. During a storm, irregular disturbances in the ionosphere cause signal scintillation, essentially making the signals flicker and fade, which degrades positioning accuracy and can cause outright signal loss.8Journal of Geophysical Research: Space Physics. Statistical Study of Loss of GPS Signals Caused by Severe and Great Geomagnetic Storms
We got a taste of this during the May 2024 storm, which was significant but still far below Carrington scale. GPS receivers in the central United States recorded position errors of up to 70 meters, and precision agricultural equipment relying on GPS guidance reported widespread outages.9Journal of Geophysical Research: Space Physics. Spatio‐Temporal Evolution of Mid‐Latitude GPS Scintillation and Position Errors During the May 2024 Solar Storm Errors that large are not just an inconvenience: they make precision farming impossible, degrade aviation instrument approaches, and create serious problems for shipping, emergency services, and any logistics system that depends on real-time positioning. A Carrington-scale storm could produce errors far larger and over far longer periods, potentially rendering GPS unreliable for hours or days across wide swaths of the planet.
GPS disruption also ripples into systems most people do not associate with satellites. Financial trading platforms use GPS timing signals to timestamp transactions to the microsecond. Cellular networks synchronize their base stations using GPS clocks. Power grids use GPS timing for protective relay coordination. Losing accurate GPS timing even briefly can cause cascading malfunctions in systems that seem completely unrelated to satellites.
Submarine Internet Cables Are Tougher Than Expected
One of the more alarming predictions that circulated in recent years was that a Carrington-scale storm could knock out the global internet by damaging undersea fiber-optic cables. The concern was reasonable on its face: these cables contain copper conductors that carry power over thousands of kilometers, making them potential targets for geomagnetically induced currents. However, recent monitoring of four transoceanic cables during periods of high solar activity found that while the cables do experience voltage changes correlated with geomagnetic disturbances, the relationship follows a near-linear pattern that allowed researchers to extrapolate the effects of a once-in-a-century event. Their conclusion was that long-haul submarine cables, regardless of length or orientation, would not be damaged during a superstorm, even one as large as the Carrington Event.10arXiv. Solar storms and submarine internet cables
That finding is reassuring, but it does not mean the internet would keep humming along. Even if the cables survive, the data centers, power substations, and network routing equipment on land still need electricity. If regional grids go down and backup generators exhaust their fuel, internet service could be interrupted not because the fiber was damaged but because the endpoints went dark. The vulnerability of the internet in a superstorm is a power problem more than a cable problem.
Radiation at Cruising Altitude
Solar energetic particles accelerated by a massive flare and coronal mass ejection would significantly increase radiation levels at commercial flight altitudes, particularly on polar routes where Earth’s magnetic shielding is weakest. During the May 2024 storm, airlines that deviated flights to lower latitudes reduced crew and passenger radiation exposure substantially. Measurements showed that without the deviation, exposure could have been up to three times higher.11Journal of Geophysical Research: Space Physics. Enhanced Radiation Exposure of Airline Crew and Passengers During the May 2024 Geomagnetic Storm
For a single flight during a moderate storm, the extra dose is small in absolute terms and not an immediate health hazard for passengers. But for flight crews who accumulate exposure over many flights, and for a Carrington-scale event where the particle flux would be far more intense, the calculus changes. Researchers have modeled the most extreme known solar particle event, a burst in 774 AD detected through tree-ring carbon-14 records, to establish a worst-case reference for radiation at flight altitudes.12Journal of Space Weather and Space Climate. Assessment of the radiation risk at flight altitudes for an extreme solar particle storm of 774 AD During an event that severe, grounding all flights at high latitudes would likely be the safest response, and it would happen fast: airlines already have protocols to reroute or ground flights when solar radiation alerts are issued, though the protocols have never been tested against a true superstorm.
The Economic Damage
Putting a dollar figure on a hypothetical catastrophe is inherently speculative, but the modeling that exists gives a sense of scale. One detailed risk assessment for the United Kingdom estimated that a Carrington-sized event with no space-weather forecasting capability could cause GDP losses as high as £15.9 billion. Current forecasting ability reduces that figure to about £2.9 billion, and enhanced forecasting investments could bring it down further to around £0.9 billion.13PubMed Central. A Risk Assessment Framework for the Socioeconomic Impacts of Electricity Transmission Infrastructure Failure Due to Space Weather: An Application to the United Kingdom Those numbers are for a single medium-sized economy; for the United States, the European Union, or the global economy as a whole, the losses would scale accordingly.
The economic damage would not come primarily from destroyed equipment, though that would be expensive. It would come from the cascade. Without power, water treatment plants stop pumping. Without GPS, supply chains stall. Without satellite communications, financial markets cannot clear transactions. Hospitals switch to generators, which need fuel, which needs trucks, which need GPS and functioning traffic systems. Each failure domain amplifies the others. The longer power stays out, the steeper the curve of compounding disruption becomes. Wide-area power failures are understood to produce exactly this kind of cascading escalation, where impacts in one sector spill into others in ways that are difficult to predict in advance and difficult to contain once they start.
Early Warning and How Much Time We Would Have
The good news is that a Carrington-class event would not arrive unannounced. Solar flares travel at the speed of light and would be detected by space-based observatories within minutes. The coronal mass ejection itself, a massive cloud of magnetized plasma, travels more slowly and would take roughly 12 to 18 hours to reach Earth for the fastest events, possibly longer for slower ones. Monitoring stations at the L1 Lagrange point, about 1.5 million kilometers sunward of Earth, can detect the incoming plasma and provide a final warning. An optimized detection system based on solar wind velocity and interplanetary magnetic field measurements has been shown to accurately identify storm onset with a false alarm rate below 2%.14URSI Radio Science Letters. Real-Time Solar Storm Onset Determination at Lagrange Point 1 (L1) Based on an Optimized Effective Pressure Parameter
However, that final warning from L1 provides only about 15 to 45 minutes of lead time before the storm hits the magnetosphere. The hours between the flare detection and the storm’s arrival would be the critical window for grid operators to take protective action: reducing loads, disconnecting vulnerable transformers, and bringing backup systems online. For satellite operators, the window would be used to put spacecraft into safe mode, orient solar panels edge-on to reduce particle exposure, and postpone any planned maneuvers.
The uncomfortable caveat is that the forecasting satellites themselves are aging. The study modeling UK economic losses noted that with existing satellites nearing the end of their operational lives, forecasting capability will degrade in coming years unless new investment is made.13PubMed Central. A Risk Assessment Framework for the Socioeconomic Impacts of Electricity Transmission Infrastructure Failure Due to Space Weather: An Application to the United Kingdom Losing forecasting ability just as solar cycle 25 approaches its peak is a risk that several space agencies are aware of but that funding has not fully addressed.
What Grid Operators Can Actually Do
Mitigation is not theoretical. New Zealand’s national grid operator, Transpower, has developed and adopted an operational procedure based on targeted line disconnections during geomagnetic storms. By selectively disconnecting specific transmission lines, the strategy reduced the average GIC at the 27 most vulnerable transformers out of the top 30 at risk, and cut total network GIC by about 16%. Simulations further showed that installing capacitor blocking devices at 14 specific transformer sites could reduce total GIC across the network by an additional 16%.15Space Weather. Geomagnetically Induced Current Mitigation in New Zealand: Operational Mitigation Method Development With Industry Input
The approach is instructive because it shows that even without exotic technology, grid operators can meaningfully reduce the damage through careful planning and pre-positioned protocols. The challenge is scale: New Zealand’s grid is relatively compact and isolated. Grids spanning the northern United States or Scandinavia, where the geomagnetic latitude makes GICs strongest, are far more complex. Developing and drilling similar operational plans for continental-scale grids is an enormous coordination problem, and one where progress has been uneven.
Birds, Navigation, and the Biological Dimension
The effects of a Carrington-scale storm would extend beyond human infrastructure. Many animal species navigate using Earth’s magnetic field, and geomagnetic disturbances measurably disrupt that ability. A large-scale study of nocturnal bird migration across the United States found that during severe space weather events, the number of birds migrating on a given night dropped by 9 to 17% in both spring and fall. During fall migration, birds also showed reduced effort flying against the wind, suggesting they were drifting rather than actively navigating. The effect was strongest when both the magnetic field was disturbed and the sky was overcast, removing the celestial cues that birds can use as a backup.16PubMed Central. Space weather disrupts nocturnal bird migration
Smaller-scale studies of European robins found a similar pattern: the birds reduced their nighttime migratory activity when magnetic conditions were disturbed, apparently waiting for conditions to improve or for daylight when visual landmarks could compensate.17PubMed Central. Magnetic storms disrupt nocturnal migratory activity in songbirds A Carrington-scale storm would create magnetic conditions far outside anything these species have evolved to handle. Whether the disruption would simply delay migration by a few days or cause significant disorientation and mortality is unknown, because nothing in modern recorded history provides a comparable data point.
Storms Bigger Than Carrington Have Happened
The Carrington Event is the standard reference point, but it is not the worst thing the sun has ever thrown at us. Tree-ring records of carbon-14 and ice-core records of beryllium-10 have revealed at least two events, in 774 AD and 993 AD, that produced rapid spikes in cosmogenic isotopes consistent with extreme solar particle events.18Nature Communications. Another rapid event in the carbon-14 content of tree rings The 774 AD event appears to have been substantially more intense than the Carrington storm. Nobody was operating a telegraph in 774 AD, so the event left no technological record, only a chemical signature in tree rings worldwide.
The existence of these events changes the risk framing. The Carrington Event is not the ceiling; it is somewhere in the middle of what the sun is capable of producing on timescales of centuries to millennia. Planning only for a Carrington repeat means potentially being underprepared for a 774 AD-class event. That is not an academic concern: the radiation dose at flight altitudes during a 774 AD-scale event has been specifically modeled as the worst-case reference scenario for aviation safety planning.12Journal of Space Weather and Space Climate. Assessment of the radiation risk at flight altitudes for an extreme solar particle storm of 774 AD
Legal and Policy Gaps
One dimension that rarely enters public discussion is whether governments are legally equipped to respond to a space weather emergency. Japan, despite being a major spacefaring nation, illustrates the problem. Its existing space-related laws, including the Basic Space Act of 2008 and subsequent legislation on spacecraft operations and satellite data, contain no explicit provisions for crisis response. There are no defined triggers for a government-led emergency response, no designated lead ministry, and no codified measures for mitigating societal impacts or ensuring rapid recovery.19Advances in Space Research. Crisis in space: Assessing Japan’s legal gaps in space emergency response Japan began establishing public-private information-sharing mechanisms in 2023, but the legal framework has not caught up.
Japan is not an outlier. Most countries treat space weather as a scientific concern rather than a civil-protection one. The United States has made more progress, with a National Space Weather Strategy and executive orders directing agencies to prepare, but the gap between policy documents and tested, drilled operational plans remains wide. A Carrington-scale event would unfold over hours, and in many countries the legal authority to order preemptive grid shutdowns, ground flights, or redirect satellite operations sits in ambiguous institutional territory. When the storm arrives, the question of who is in charge would be answered on the fly, and that is not how you want to handle a continental-scale infrastructure emergency.