A powerful reminder of the potentially devastating effects of severe space weather arrived on May 31, 2025, when a coronal mass ejection (CME) from Earth’s Sun triggered a weather alert covering the entire planet.
The first indication of the incoming geomagnetic storm was observed by the U.S. Naval Research Laboratory (NRL) using space-based instruments such as LASCO and CCOR-1. While CMEs can produce stunning auroras, they also pose serious risks to Earth’s electrical and satellite infrastructure.
Geomagnetic Storms
“Our observations demonstrated that the eruption was a so-called ‘halo CME,’ meaning it was Earth-directed, with our preliminary analysis of the data showing an apparent velocity of over 1,700 kilometers per second for the event,” stated Karl Battams, Ph.D., computational scientist for NRL’s Heliospheric Science Division.
Geomagnetic storms occur when the solar wind delivers a surge of powerful energy from the Sun into Earth’s space environment, disturbing the magnetosphere. In extreme cases, the energy can tear open Earth’s magnetic shield. The recent event was so intense that the National Oceanic and Atmospheric Administration (NOAA) classified it as a G4-level storm—the second-highest on the geomagnetic scale. Despite its strength, the G4 event moved relatively slowly but was directed squarely at Earth. As a result, auroras were seen as far south as New Mexico.
“CMEs are the explosive release of mass from the Sun’s low corona and are a primary driver of space weather, playing a central role in understanding the conditions of the Earth’s magnetosphere, ionosphere, and thermosphere,” explained Arnaud Thernisien, Ph.D., a research physicist in the Advanced Sensor Technology Section of NRL’s Space Science Division.
During a CME, billions of tons of solar material are ejected in an eruption of plasma and magnetic field. While a typical CME may take days to reach Earth, the fastest events can arrive in just 18 hours, leaving little time for warning or mitigation.
Space Weather Impacts
Once CMEs complete their 94.4 million-mile journey from the Sun to Earth, their effects on ground- and space-based systems can be significant. Depending on their strength, CMEs can disrupt or disable electrical systems, corrupt data, and interrupt communications. Critical systems like timing and GPS are especially vulnerable. These storms can also exert direct physical effects, such as increasing atmospheric drag on satellites or even causing permanent damage to space-based assets.
“Such disturbances can compromise situational awareness, hinder command and control, affect precision-guided systems, and even impact the electrical power grid, directly affecting military readiness and operational effectiveness,” Battams said.
Detecting CMEs
NRL’s Large Angle Spectrometric Coronagraph (LASCO) and the Compact Coronagraph 1 (CCOR-1) are two of the most important tools for detecting recent CMEs. These instruments, along with others like the Parker Solar Probe, provide critical data that space weather forecasters use to predict when CMEs will arrive and how severely they might impact Earth. Though precise forecasting remains difficult, early detection is key to issuing timely alerts and safeguarding vulnerable infrastructure.
“They form the backbone of our ability to anticipate and mitigate the effects of space weather. As the G4 severe geomagnetic storm watch continues, the public and critical infrastructure operators are encouraged to visit NOAA’s Space Weather Prediction Center for the latest information and updates,” Thernisien said.
“NRL has been a pioneer in heliophysics and space weather research since the very inception of the field, dating back to the first discovery of CMEs through NRL space-based observations in 1971,” Battams said. “Since then, NRL has consistently maintained its position at the forefront of coronal imaging with a portfolio of groundbreaking instrumentation that has driven heliospheric and space weather studies.”
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.