When the sun emits more energy than normal, the effects range from barely measurable warmth increases on Earth to catastrophic disruptions of power grids, satellites, and communication systems. The difference depends on whether the extra energy comes from the sun’s gradual 11-year brightness cycle or from sudden, violent events like solar flares and coronal mass ejections. The quiet variations nudge Earth’s climate by a tiny fraction. The explosive ones can knock out infrastructure across entire continents.
The Sun’s 11-Year Energy Cycle
The sun doesn’t burn at a perfectly constant rate. It follows a roughly 11-year cycle between periods of low activity (solar minimum) and high activity (solar maximum). At solar maximum, the sun’s total brightness is about 0.1 percent higher than at solar minimum, which translates to around 1 extra watt per square meter reaching Earth. Day-to-day fluctuations can be larger, up to 0.3 percent, but averaged over time, the swing is small.
That 0.1 percent sounds trivial, and in terms of direct heating, it is. Solar variations contribute a small amount of warming compared to the effect of greenhouse gases. But even this modest change matters at the margins. It slightly shifts the energy balance of the upper atmosphere, influences weather patterns in subtle ways, and drives cycles of ultraviolet radiation that affect the ozone layer. The sun’s cycle also controls how frequently the more dramatic events occur.
Solar Flares and Radio Blackouts
Solar flares are sudden bursts of radiation from the sun’s surface, and they represent a very different kind of “extra energy” than the gentle cycle. Flares are classified on a scale from A (weakest) to X (strongest), with each letter representing a tenfold increase in X-ray intensity. An X1 flare produces X-ray flux of 0.0001 watts per square meter at Earth orbit. An X20 flare, classified as extreme, hits 0.002 watts per square meter.
The immediate effect of a strong flare is disruption to radio communications. X-rays from the flare slam into Earth’s upper atmosphere and ionize it, absorbing high-frequency radio signals. During an extreme flare (X20 or higher), high-frequency radio can go completely dead across the sunlit side of the planet. Airlines lose contact with transoceanic flights. Maritime communications drop. Emergency radio systems go silent. These blackouts can last minutes to hours, depending on the flare’s intensity and duration.
Coronal Mass Ejections and Geomagnetic Storms
The more consequential events happen when the sun doesn’t just release radiation but physically hurls billions of tons of charged particles into space. These coronal mass ejections (CMEs) travel at hundreds to thousands of kilometers per second and, if aimed at Earth, slam into our planet’s magnetic field one to three days after launch. The collision compresses and distorts the magnetic field, triggering what’s called a geomagnetic storm.
NOAA rates geomagnetic storms on a G1 to G5 scale. At G1 (minor), you get weak power grid fluctuations and aurora visible in northern Michigan and Maine. At G3 (strong), voltage corrections become necessary across power systems, satellite navigation becomes unreliable, and the aurora can be seen as far south as Illinois and Oregon. These strong storms happen roughly 200 times per 11-year cycle.
At G5 (extreme), the picture gets serious. Power grids can experience complete collapse. Satellite navigation may degrade for days. High-frequency radio can become unusable for one to two days across large areas. Aurora has been observed as far south as Florida and southern Texas. These extreme storms are rare, occurring about 4 times per solar cycle, but their consequences are outsized.
How Solar Storms Damage Power Grids
The mechanism behind grid damage is surprisingly direct. When a geomagnetic storm distorts Earth’s magnetic field, it induces electric currents in the ground. These geomagnetically induced currents (GICs) flow up through the grounded connections of large power transformers. Transformers are designed to handle alternating current, not the slow, steady direct current that GICs produce. Even small amounts of this unwanted current can push a transformer’s iron core into saturation, a state where the core can no longer contain its magnetic field properly.
Once saturated, magnetic flux leaks out of the core and flows through the transformer’s structural components, including the metal tank surrounding it. This generates intense localized heating. The windings overheat, insulation breaks down, and the transformer can be permanently destroyed. A single large power transformer costs millions of dollars and can take over a year to manufacture and install. If a major storm damages dozens of them simultaneously across a region, the resulting blackout could last weeks or longer, not because the storm persists, but because the hardware is physically broken.
Certain transformer designs are especially vulnerable. Autotransformers, commonly used in high-voltage transmission, provide no electrical isolation between their windings. GICs entering one part of the system can flow freely into connected networks, spreading the damage further than the initial point of entry.
Effects on Satellites and GPS
Satellites sit outside Earth’s protective atmosphere and take the full force of increased solar energy. During strong storms, charged particles bombard satellite surfaces, building up electrical charges that can arc across components and damage electronics. Satellites in low Earth orbit also experience increased atmospheric drag because the upper atmosphere heats up and expands during solar events, slowing the spacecraft and altering their orbits. Tracking and communication links with ground stations can be disrupted, and orientation systems may lose their reference points.
GPS accuracy suffers noticeably during geomagnetic storms. The charged particles disturb the ionosphere, the atmospheric layer that GPS signals pass through, introducing delays that throw off position calculations. During strong ionospheric disturbances, GPS positioning errors can jump to nearly 1 meter. When scintillation (rapid signal fluctuation) becomes intense, average errors exceed 0.8 meters. For everyday navigation that’s manageable, but for precision agriculture, surveying, autonomous vehicles, and aircraft landing systems, errors of that magnitude are a real problem.
What a Worst-Case Scenario Looks Like
The benchmark for a worst-case solar event is the Carrington Event of 1859, the most powerful geomagnetic storm in recorded history. Telegraph systems across North America and Europe failed. Operators received electric shocks. Some telegraph machines continued transmitting even after being disconnected from their power supplies, running entirely on the current induced by the storm.
If an equivalent event struck today, the consequences would be far more severe. According to the U.S. Geological Survey, such a storm could disrupt telecommunications and power transmission across the United States, with the Midwest and East Coast especially vulnerable. Magnetic field strengths in some areas would be enough to stress or damage high-voltage transformers, potentially triggering massive power outages. Flights at multiple airports could be delayed or canceled. Satellite systems could falter. And because modern infrastructure is deeply interconnected, a single failure could cascade across networks.
In a best case, disruptions might last seconds or minutes. In a worst case, they could persist for days or weeks. USGS geophysicist Jeffrey Love has noted that an intense storm could be far more hazardous than what the power transmission industry is currently prepared for. Near-miss events have reinforced this concern: in July 2012, a Carrington-class CME crossed Earth’s orbital path just one week after our planet had moved through that spot.
The Climate Question
A common question behind this search is whether increased solar energy could be driving climate change. The short answer: the sun’s energy variations are real but small compared to the warming caused by greenhouse gases. The 0.1 percent brightness change across the solar cycle translates to a radiative forcing (the push on Earth’s energy balance) that is minor next to the forcing from carbon dioxide and other heat-trapping gases accumulated since the industrial era. Solar output has caused a little additional warming since the mid-1700s, but it accounts for only a small fraction of the temperature increase observed over the past century.
Where solar variability does matter is in shorter-term climate patterns. Small shifts in ultraviolet output during the solar cycle influence stratospheric chemistry, which can ripple down into weather patterns. Some research links solar cycles to regional precipitation and temperature variations. But these effects layer on top of the much larger greenhouse gas signal rather than replacing it.