Evrim Yazgin
Cosmos science journalist
Observation of 2 strong solar flares within 24 hours has led NASA to issue warnings that the intense eruptions on the Sun’s surface could cause problems on Earth.
The first flare was spotted by NASA’s Solar Dynamics Observatory at 1:38am AEST, Wednesday 14 May (11:38am ET, 13 May). The second was imaged at 6:25pm AEST (4:25am ET) on 14 May.
How strong is strong?
Both flares belong to the highest category, X, of solar flare strength. The first was measured at X1.2, and the second was an X2.7.
Solar flares come in 5 strength categories – A, B, C, M and X. Each letter in this scale represents a flare 10 times greater in strength than the previous letter. The number next to the letter is a further scale factor – i.e. an X2.7 is 2.7 times stronger than an X1.
Activity on the Sun’s surface is cyclic. Every 11 years, our central star reaches “solar maximum” when this activity peaks. Experts from NASA, the National Oceanic and Atmospheric Administration (NOAA) and the Solar Cycle Prediction panel confirmed in October 2024 that the Sun had reached solar maximum for this cycle – the 25th recorded.
Solar maximum is marked by increased sunspots, solar flares and coronal mass ejections.
While Solar Cycle 25’s maximum is not predicted to be particularly violent, experts say that satellites, GPS systems, radio networks and power grids are all at risk if solar flares shoot high-speed particles in Earth’s direction. Strong flares can also pose a direct risk to spacecraft and astronauts.
In 2023, an X1-class flare caused a 30-minute radio blackout across the Pacific Ocean and the western US.
Unpredictable star
Devika Kamath, an associate professor in astronomy and astrophysics at Macquarie University in Australia, tells Cosmos that observations of the Sun help space weather scientists determine when effects might be felt on Earth.
“The Sun is continuously monitored by a network of solar observatories in space,” Kamath says. “These observatories provide near real-time data, allowing us to detect solar flares – sudden bursts of high-energy radiation – and track coronal mass ejections (CMEs), which are huge clouds of magnetised plasma ejected from the Sun.”
But Kamath says there is still a lot of uncertainty.
“However, not every flare or CME affects Earth. Whether we experience impacts depends largely on 2 things: whether the CME is actually heading toward Earth, and whether its magnetic field is oriented in a way that can effectively interact with Earth’s own magnetic field. If that alignment is just right, it can trigger significant geomagnetic storms.
“If a CME is confirmed to be on a collision course with Earth, we usually get 12 to 72 hours’ notice—long enough to alert vulnerable sectors, but not always enough to predict the severity or location of impact with high confidence.
“So, while we can monitor solar activity in real time and forecast the likelihood of an impact, predicting exactly which flare will cause trouble remains a complex and evolving challenge.”
Kamath explains that it’s even harder to predict when solar flares are going to erupt.
“We can estimate the likelihood of a flare by monitoring large, magnetically complex sunspot regions – these are the usual sources of flare activity. For example, Australia’s Bureau of Meteorology issues daily forecasts showing the chances of moderate or strong flares based on current solar conditions.
“But the exact timing, strength, or impact of a flare remains unpredictable. That’s because flares are triggered by sudden, chaotic changes in the Sun’s magnetic field. Research is advancing, especially with machine learning and data-driven modelling, but for now, we can only flag when conditions are favourable – not when a flare will actually occur.”
An eye on Australia
“Solar activity can and does affect Australia,” Kamath says. “Sitting at mid-latitudes, Australia is less exposed to the most intense geomagnetic effects than high-latitude regions like Canada or Scandinavia. Still, we’re far from immune.”
Kamath says the most relevant risks in Australia are GPS and satellite navigation errors, high-frequency radio blackouts effecting aviation, maritime operations and emergency services, satellite anomalies which may impact weather forecasting and communications, and geomagnetically induced currents which pose a risk to sensitive power grid infrastructure.
“Australia benefits from some natural shielding due to its location, but our increasing reliance on space-based technologies and long-range communication systems means space weather remains a serious and evolving concern,” Kamath explains.
Historical precedent and modern problems
“The worst-case scenario involves a severe solar storm – something on the scale of the 1859 Carrington Event – which could disrupt satellite operations and global communications, damage power grids and cause blackouts, and interrupt aviation, GPS, financial systems, and internet connectivity.”
The Carrington Event is the greatest solar flare incident of the last 500 years. It is named after English astronomer Richard Carrington who spotted two beads of blinding white light appear over sunspots during his observations. The next morning, the planet was cloaked in red, green and purple auroras and telegraph systems disrupted.
Scientists estimate that the Carrington Event was caused by a class X45 solar flare.
“We’ve already seen serious modern examples,” adds Kamath. “In 1989, a powerful solar storm caused the Quebec blackout, leaving 6 million people without power for 9 hours. The Halloween Storms of 2003 disrupted satellites, grounded flights, and even forced astronauts on the ISS into shielded areas due to heightened radiation levels.”
Globally, scientists are trying to better understand solar activity to be able to predict and prepare for disruptive events.
“To mitigate these risks, Australia relies on the Bureau of Meteorology’s Space Weather Services, which issue alerts and warnings to critical sectors such as aviation and energy,” Kamath explains.
“Geoscience Australia operates a network of geomagnetic observatories that monitor Earth’s magnetic response, while facilities like Culgoora and Learmonth provide real-time solar data to support forecasting and response. Infrastructure operators – including grid managers and satellite service providers – have established protocols for periods of heightened solar activity.
“While we cannot eliminate all risk, growing international collaboration and Australian-led space weather capabilities continue to improve resilience across critical sectors.”
