Solar flares are more frequent right now than they have been in over two decades. Solar Cycle 25, the current roughly eleven-year cycle of rising and falling solar activity, has exceeded most early forecasts and is producing powerful flares on a regular basis, with multiple models placing its peak around mid-2024 to early 2025 at a sunspot number near 130 to 145. That activity has real consequences for technology, navigation, aviation, and even future crewed missions to the Moon, and the science of predicting and measuring flares is evolving fast enough to be worth a closer look.
What Actually Happens During a Solar Flare
A solar flare is, at its core, a sudden release of energy stored in twisted magnetic fields on the Sun’s surface. When magnetic field lines in an active region become tangled and stressed enough, they can snap and reconnect in a process called magnetic reconnection, converting that stored magnetic energy into intense radiation, plasma heating, and accelerated particles launched outward at tremendous speed.1The Astrophysical Journal. Determining the 3D Dynamics of Solar Flare Magnetic Reconnection The energy released travels across nearly the entire electromagnetic spectrum, from radio waves to gamma rays, and the most energetic particles can reach Earth in under an hour.
The reconnection itself is not an instantaneous event. Studies of large flares show that reconnection rates ramp up through a main rise phase, peaking near the end of that phase and correlating tightly with the energy dumped into high-energy electrons.2Astronomy & Astrophysics. Coupling between magnetic reconnection, energy release, and particle acceleration in the X17.2 2003 October 28 solar flare High-resolution solar observations have also revealed precursor brightenings at small magnetic structures near the footpoints of sheared magnetic loops, hinting that subtle low-atmosphere energy releases can serve as early warning signals before the main eruption.3Monthly Notices of the Royal Astronomical Society. High-resolution observations of flare precursors in the low solar atmosphere Understanding those precursors is one of the open frontiers of flare research.
How Flares Are Classified
Solar flares are grouped by their peak X-ray brightness as measured by the GOES satellites in orbit around Earth. The scale runs through letter classes: A, B, C, M, and X, with each letter representing a tenfold jump in power. A C-class flare is ten times weaker than an M-class, and an M is ten times weaker than an X. Within each class, a number from 1 to 9 gives further resolution, so an M5 flare is halfway up the M range. The X class has no upper cap; the famous 2003 Halloween storm included a flare initially estimated above X28.
For everyday life, C-class flares are too weak to cause noticeable effects. M-class flares can produce brief radio blackouts, and X-class flares are the ones capable of widespread disruptions to communications, GPS, and power infrastructure. Automated forecasting systems that scan X-ray flux data aim to predict which active regions will produce these larger events.4Space Weather. UFCORIN: A fully automated predictor of solar flares in GOES X‐ray flux
Flares and Coronal Mass Ejections Are Not the Same Thing
A common source of confusion is the relationship between solar flares and coronal mass ejections (CMEs). Both originate in magnetically active regions on the Sun, and they often occur together, but they are distinct phenomena. A flare is essentially a flash of radiation. A CME is a massive cloud of magnetized plasma hurled outward from the Sun’s corona. Not every flare triggers a CME, and some CMEs occur without an obvious flare.5Data in Brief. Integration of solar flare and coronal mass ejection event data
The distinction matters because their effects on Earth arrive on different timescales. The radiation from a flare reaches Earth in about eight minutes, traveling at the speed of light, and can immediately disrupt radio communications. A CME, by contrast, takes one to three days to cross the same distance, but when it arrives it can trigger a geomagnetic storm that affects power grids, satellites, and produces auroras. The worst space weather events tend to involve both a strong flare and an Earth-directed CME, compounding the impacts.
Where Solar Cycle 25 Stands
The Sun’s activity waxes and wanes over a roughly eleven-year cycle, and Solar Cycle 25 has turned out to be more active than many early predictions suggested. Multiple independent forecasting models now place the peak sunspot number in the neighborhood of 130 to 145. One neural network-based forecast predicted a peak of about 131 to 137 sunspots around mid-2024, noting the cycle would be slightly stronger than Cycle 24 but weaker than Cycle 23.6Solar Physics. Forecasting Solar Cycle 25 with Physical Model-Validated Recurrent Neural Networks A separate data-assimilation approach converged on a solar maximum between mid-2024 and early 2025 with a sunspot number around 143.7Astronomy & Astrophysics. Forecasting the solar cycle using variational data assimilation: Validation on cycles 22 to 25
In practical terms, this means we are at or very near solar maximum right now, and the Sun has been producing X-class flares and significant CMEs with regularity. The May 2024 geomagnetic storm, driven by a series of powerful eruptions, was among the strongest in two decades and produced auroras visible from locations far closer to the equator than usual. Activity at this level is expected to taper gradually over the next few years as the cycle winds down, though individual large events remain possible well past the statistical peak.
How Flares Are Monitored Today
The traditional workhorse for flare detection is the GOES satellite network, which continuously measures solar X-ray flux and provides the data behind the classification system. But the monitoring toolkit has expanded considerably. The AGILE space telescope, originally designed for gamma-ray astronomy, developed a real-time pipeline that scans its hard X-ray data for minute-lasting transients and automatically alerts its team when a candidate solar flare is detected.8The Astrophysical Journal Supplement Series. The First AGILE Solar Flare Catalog Ground-based radio observatories, including stations in the global e-Callisto network, provide near-real-time readings of coronal magnetic conditions and particle acceleration during events, offering complementary data to spacecraft instruments.9Space Weather. Ground‐Based Solar Radio Observations From the Mexican e‐Callisto Stations During the May 2024 Extreme Space Weather Events
One of the more surprising monitoring tools is the GPS constellation itself. Researchers discovered that the worldwide network of GPS receivers can be repurposed as a solar observatory. When a flare’s extreme ultraviolet radiation hits Earth’s atmosphere, it causes a sudden increase in the ionosphere’s electron content. By analyzing dual-frequency phase measurements from hundreds of ground receivers, scientists can detect flares and quantify the ultraviolet flux in real time, sometimes with advantages over dedicated spacecraft instruments.10Space Weather. Real‐Time Detection, Location, and Measurement of Geoeffective Stellar Flares From Global Navigation Satellite System Data: New Technique and Case Studies The approach was validated for strong, medium, and weak flares alike.11Journal of Geophysical Research: Space Physics. GPS as a solar observational instrument: Real‐time estimation of EUV photons flux rate during strong, medium, and weak solar flares
AI-Driven Flare Forecasting
Predicting exactly when a solar flare will erupt remains one of the hardest problems in space weather. The Sun’s magnetic fields are chaotic, and the conditions that trigger reconnection are not yet understood well enough to forecast events the way we forecast terrestrial weather. But machine learning has made real progress. Deep learning models trained on images of the Sun’s magnetic field, known as magnetograms, spanning two full solar cycles have shown strong predictive performance for distinguishing active regions likely to produce large flares.12The Astrophysical Journal. Predicting Solar Flares Using CNN and LSTM on Two Solar Cycles of Active Region Data
A persistent criticism of these models has been that they function as “black boxes,” providing predictions without explaining what physical features they are actually responding to. Recent work using explainable AI techniques has started to crack that open. By applying gradient-weighted activation mapping to trained neural networks, researchers identified which regions of magnetograms the models focused on and found that the magnetic features in those regions had genuinely high predictive power for flares. In other words, the networks were learning physically meaningful patterns, not just noise or artifacts.13The Astrophysical Journal Letters. Explainable AI for Solar Flare Prediction: Quantitative Magnetic Field Analysis of Model-focused Regions This is an encouraging sign that AI-based forecasting might eventually provide both accurate warnings and insight into the physics of flare initiation.
Radio Blackouts and Communication Disruptions
The most immediate terrestrial effect of a solar flare is disruption to high-frequency radio communications. When X-ray and ultraviolet radiation from a large flare hits the dayside of Earth, it ionizes the lower layers of the ionosphere, dramatically increasing how much those layers absorb radio waves. For a strong flare, the result is an abrupt blackout of shortwave radio on the sunlit hemisphere.
During the September 2017 solar storm, a series of X-class flares on September 6, 7, and 10 caused acute radio blackouts across the Caribbean, with recovery times ranging from tens of minutes to hours depending on how quickly each flare’s X-ray emission decayed.14Space Weather. High‐Frequency Communications Response to Solar Activity in September 2017 as Observed by Amateur Radio Networks Modeling of the D-region ionosphere during those events suggested absorption levels of roughly 20 to 40 decibels at common shortwave frequencies, consistent with observed conditions and exceeding what operational prediction models anticipated.15Space Weather. Tests of a New Solar Flare Model Against D and E Region Ionosphere Data Aviation and maritime sectors, which still rely on high-frequency radio for long-distance communications over oceans, are particularly exposed to these disruptions.
GPS Accuracy and Navigation
Solar flares and the geomagnetic storms they sometimes trigger can degrade GPS positioning accuracy, though the relationship is less straightforward than many popular accounts suggest. The mechanism works through ionospheric disturbances. When the ionosphere becomes disturbed, GPS signals passing through it experience scintillation, which refers to rapid fluctuations in signal strength and phase. These fluctuations increase cycle slips in GPS receivers and can reduce the number of usable satellites, leading to poorer positioning solutions. Analysis of the September 2017 events confirmed that precise point positioning accuracy degraded at stations in both low and high latitudes during flare periods.16Advances in Space Research. Ionosphere disturbances on GNSS signal and positioning performance: Analysis of the solar flare and geomagnetic storm events in September 2017 and October 2021
The picture gets more nuanced with CME-driven geomagnetic storms. A case study of a full-halo CME event found that scintillation and positioning errors were more pronounced at mid and high latitudes than at low latitudes, and that even storms that do not produce visible scintillation can still degrade accuracy through other pathways like data outages and measurement noise.17Advances in Space Research. Analysis of global ionospheric scintillation and GPS positioning interference triggered by full-halo CME-driven geomagnetic storm: A case study
Counterintuitively, multi-year observations have revealed that on the day of peak solar flare activity, GPS positioning can actually show a slight improvement. The reason involves a nonlinear relationship between solar radiation levels and scintillation intensity: above a certain threshold of extreme ultraviolet flux, stronger radiation can suppress ionospheric scintillation rather than amplify it, temporarily smoothing out the irregularities that degrade signals.18Space Weather. Solar Activity Impacts on Ionospheric Scintillation and Precise Point Positioning Based on Multi‐Year GNSS and Scintillation Observations This does not mean flares are good for GPS; the geomagnetic storms that often follow can cause much worse disruption than the initial flare.
Power Grid Vulnerability
When a CME triggers a geomagnetic storm, rapidly changing magnetic fields at Earth’s surface induce electric currents in long conductors like high-voltage transmission lines and pipelines. These geomagnetically induced currents, or GICs, flow through transformer windings and can saturate transformer cores, causing overheating, increased reactive power demand, and in severe cases, permanent damage. Grid operators model these risks by calculating the geoelectric fields induced by specific storm scenarios and mapping how the resulting currents would flow through their transmission networks.19Journal of Atmospheric and Solar-Terrestrial Physics. Management of the geomagnetically induced current risks on the national grid company’s electric power transmission system
The economic stakes go beyond the cost of replacing damaged equipment. Studies that account for indirect effects, including supply chain disruptions and lost production, find that indirect costs can roughly equal or exceed the direct costs of the power outage itself.20Space Weather. Quantifying the daily economic impact of extreme space weather due to failure in electricity transmission infrastructure A review of the evidence across multiple countries confirmed that production interruptions and market cascades, not physical infrastructure damage, drive the bulk of total economic losses from space weather events.21Frontiers in Astronomy and Space Sciences. Impact of space weather on electricity power grids: a review on economic consequences and national policy For a small, trade-dependent economy like New Zealand, modeling of an extreme unmitigated storm estimated GDP losses reaching roughly one percent of annual output.22arXiv. Assessing the economic benefits of space weather mitigation investment decisions: Evidence from Aotearoa New Zealand
How a Carrington-Class Storm Compares
The 1859 Carrington Event is the benchmark for extreme space weather. Telegraph systems across North America and Europe were disrupted, with some operators reporting sparks and fires. How would a storm of that magnitude compare to more recent severe events? Modeling focused on Fennoscandia estimates that a Carrington-class storm could generate geoelectric fields roughly 1.4 to 20 times larger than those from the 2003 Halloween storm, with an average ratio around seven times larger.23J. Space Weather Space Clim.. Comparison of the modelled geoelectric fields of the Carrington and Halloween storms That wide range reflects differences in local geology and the orientation of the storm’s magnetic field, but even the low end represents a significant escalation over what modern grids have actually experienced.
The concern is not hypothetical. Simulations of extreme events affecting the North American power grid suggest that cascading outages could spread across the eastern United States and Canada within the first hour, with transformer failures compounding the problem. Because large high-voltage transformers are custom-built, have long lead times, and are barely manufactured domestically in most countries, full grid recovery from a worst-case event could take months rather than days.
Radiation at Flight Altitudes
Airline passengers and crew are normally exposed to elevated background radiation compared to people on the ground, simply because there is less atmosphere above them to block cosmic rays. During a solar particle event, that exposure can spike. The May 2024 geomagnetic storm provided real-world measurements: onboard radiation sensors on a commercial flight recorded sporadically high absorbed dose rates, and modeling showed that radiation exposure could have been up to three times higher if the airline had not rerouted the flight to lower latitudes as a precaution.24Journal of Geophysical Research: Space Physics. Enhanced Radiation Exposure of Airline Crew and Passengers During the May 2024 Geomagnetic Storm Airlines increasingly receive space weather advisories that allow them to alter routes, particularly on polar flights where exposure is highest.
For context, the single-event exposure from even a severe modern solar storm during a normal flight is small relative to the career limits set for radiation workers. The larger concern is for frequent flyers and flight crew who accumulate many exposures over years, and for the rare possibility of an event far stronger than anything in the modern record. Modeling of the most extreme known solar particle storm, estimated from the year 774 AD based on isotopes in tree rings, found that such an event would deliver a much more significant dose at aviation altitudes.25Journal of Space Weather and Space Climate. Assessment of the radiation risk at flight altitudes for an extreme solar particle storm of 774 AD
Radiation Risks for Astronauts on the Moon
Outside Earth’s magnetic shield, the radiation picture changes dramatically. Solar particle events are one of the most serious hazards for crewed missions beyond low Earth orbit, and they are especially concerning for future lunar exploration. Earth’s magnetic field and atmosphere provide substantial protection; the Moon has essentially neither.
A study modeling the body effective dose from 262 large historical solar particle events found that the doses astronauts would receive on the lunar surface depend heavily on shielding depth, which could come from regolith or aluminum structures.26Space Weather. The Radiation Impact of Solar Energetic Particle Events on the Moon: A Statistical Study Using Data‐Based Modeling Results In the worst historical case, the August 1972 event, simulations of an astronaut in a spacesuit-equivalent level of shielding estimate a whole-body dose equivalent of about 670 millisieverts from protons alone. Under thicker shielding equivalent to a spacecraft module, the worst exposure drops to around 100 millisieverts, associated with the February 1956 event rather than the 1972 one, because the higher-energy particles of the 1956 event penetrated deeper shielding more effectively.27Space Weather. Simulations of Radiological Dose Quantities in Astronauts During Solar Energetic Particle Events Across Modern Space History For reference, many space agencies set a career radiation limit in the range of 600 to 1,000 millisieverts, meaning a single poorly shielded event could consume most of an astronaut’s allowance at once.
Auroras Appearing at Unusual Latitudes
One of the more visible and publicly exciting effects of strong solar activity is auroras showing up far from the Arctic or Antarctic. During geomagnetic storms, the auroral oval expands equatorward, and the character of the aurora changes with latitude. The red auroras photographed from subtropical locations during storms like the April 2023 event result from a combination of a slight expansion of the oval and high-altitude red emissions produced by low-energy electron precipitation.28The Astrophysical Journal. Low-latitude Auroras: Insights from 2023 April 23 Solar Storm The red color dominates at lower latitudes because the relevant oxygen emission comes from altitudes above about 200 kilometers, where the atmosphere is thin enough for the excited oxygen atoms to radiate before colliding with anything. At higher latitudes, denser lower-altitude emissions produce the more familiar green and purple displays.
Social media has made low-latitude auroras far more visible to the public than they were even a decade ago, and during the May 2024 storm, photographs of red and pink skies flooded platforms from users across the continental United States, southern Europe, and even parts of northern Africa. These events are rare enough to be genuinely spectacular but are a normal part of the most active phases of a solar cycle. With Cycle 25 still near its peak, chances for another such display over the next year or two remain elevated compared to the quiet phase of the cycle.