In 2012, Michael Kelly, a space scientist at the Johns Hopkins University Applied Physics Laboratory, read an account of a 2002 battle in Afghanistan that claimed the lives of three United States Soldiers.
Kelly learned that a U.S. Chinook helicopter on a mission to help pinned down Navy SEALs during Operation Anaconda did not receive messages warning it away from a snowy mountain peak held by the enemy. The Chinook, which carried 21 men, crash-landed under heavy fire. Three Soldiers died in the ensuing firefight.
Kelly wondered: Why were the U.S. military’s satellite communications disrupted during the operation? Initially, the problems were ascribed to the helicopter’s radio or interference from the mountainous terrain. Kelly’s theory: Space weather may have obstructed repeated attempts to warn the Chinook away from the landing zone.
Space weather refers to conditions on Earth and in the solar system produced by the sun’s activity. Our star’s electrically charged plasma constantly streams toward the planets as solar wind, pouring energy into near-Earth space, according to a December 10, 2021, story by Vanessa Thomas at NASA.gov. Events such as solar flares (explosions on the sun’s surface) and coronal mass ejections (CMEs, which are eruptions of clouds of solar plasma and magnetic fields) can lead to geomagnetic and solar radiation storms. Researchers know that this range of phenomena can interfere with radio transmissions, satellite communications, GPS systems and even power grids. At its most extreme, space weather can endanger U.S. national security.
“Space isn’t empty like we often think,” Alexa Halford, space physics researcher at the Goddard Space Flight Center in Greenbelt, Maryland, told Thomas in the NASA story. “The study of space weather is really just trying to understand the space environment around us, like we try to understand terrestrial weather.”
Kelly, in a 2014 paper with collaborators published in the American Geophysical Union (AGU) journal Space Weather, found that equatorial plasma bubbles (EPBs) could have contributed to communications disruptions during the large-scale operation in Afghanistan. In a September 2014 news release announcing Kelly’s research, the AGU described the well-known phenomenon as “wispy clouds of electrically charged gas particles” that form in Earth’s ionosphere, the boundary between the planet’s lower atmosphere and space that starts about 80 kilometers above Earth. The bubbles, which are not visible to the human eye, are normally about 100 kilometers wide, according to the news release. The ionosphere, which is vital to communications and navigation, is so named because the atmosphere and molecules in it are ionized by solar radiation.
In a story published in January 2025, the astronomy website EarthSky describes how EPBs form after sunset when the upper atmosphere experiences a dramatic decrease in ionization: “As positive and negative ions recombine, they create a layer of lower-density air. This less-dense air layer rises through more heavily ionized layers above, due to convection. … The rising motion in Earth’s upper air creates a turbulent, bubble-like structure.”
In the case of Operation Anaconda, Kelly’s paper pointed out that it also took place at the peak of Solar Cycle 23.
EarthSky.com describes the solar cycle as a “natural cycle the sun goes through as it transitions between low and high magnetic activity. Roughly every 11 years, at the height of the cycle, the sun’s magnetic poles flip. … And the sun transitions from being calm to an active and stormy state.”
During battle on the Afghan mountaintop, the “ionosphere … was disturbed and could have affected UHF Satellite Communications (SATCOM).”
“I wasn’t really expecting to find that there was a space weather impact,” Kelly said. “But everything we found was kind of consistent with that possibility, so we kept digging.”
Cause and effect
The sun constantly blasts out charged particles and electromagnetic radiation. With this bombardment comes another constant — the chance of disruption on our planet.
“The most extreme space weather event would be a very large solar eruption causing a large, fast CME to launch directly toward the Earth,” Thomas E. Berger, executive director of the Space Weather Technology, Research and Education Center at the University of Colorado Boulder, told Apogee.
A 2020 report from the Congressional Research Service found that space weather can have repercussions ranging from low Earth orbit to the deep sea. The report said that effects may include “physical damage to satellites or orbital degradation, accelerated corrosion of gas pipelines, disruption of radio communications, damage to undersea cable systems or interference with data transmission, permanent damage to large power transformers essential to electric grid operations, and radiation hazards to astronauts in orbit.”
Still, the report notes that while space weather may affect substantial portions of Earth, hazardous events are not common. There are exceptions.
Spontaneous explosions
During the Vietnam War, the crew of a U.S. surveillance aircraft observed 20 to 25 explosions in about 30 seconds in the waters off Hon La on August 4, 1972, according to a November 2018 story by Newsweek magazine. They also witnessed 25 to 30 mud spots that indicated explosions. The blasts came in an area where the U.S. Navy had deployed sea mines (Operation Pocket Money) against North Vietnamese ports, according to Newsweek.
What caused the detonations wasn’t immediately clear.
The sea mines were of the “magnetic influence” type — designed to detonate when their sensors detected a change in the magnetic field such as that of a passing ship. The commander of the U.S. Pacific Fleet asked about a hypothesis that solar activity could have triggered the submerged mines.
There was a “high degree of probability that all the sensitive and some insensitive DSTs [mines in] NVN [North Vietnamese] waters had been detonated by the solar storm activity in early August,” concluded a then-classified report by the Department of the Navy. Decades later, scientists confirmed those conclusions.
“In researching these events we determined that the widespread electric- and communication-grid disturbances that plagued North America and the disturbances in Southeast Asia late on 4 August likely resulted from propagation of major eruptive activity from the sun to the Earth. The activity fits the description of a Carrington-class storm minus the low-latitude aurora reported in 1859,” according to a 2018 study by Delores J. Knipp and collaborators published in the journal Space Weather. Knipp is a research professor of space physics at the University of Colorado Boulder.
Still, the incident has precedent when it comes to disruptive or even dangerous events attributed to space weather.
The Carrington Event
The 1859 incident takes its name from English astronomer Richard C. Carrington, who observed an intense flash of light near sunspots that hours later would result in a wave of auroras that would light the night skies in North America and as far south as Colombia.
“People read newspapers by the light. … Instruments that measure changes in Earth’s magnetism are acting crazy, their needles pinned off-scale,” according to the National Oceanic and Atmospheric Administration (NOAA) educational website SciJinks. There were even reports of telegraph machines erupting in sparks, according to the website.
The flare was a huge CME that traveled more than 150 million kilometers in just 17.6 hours before its force caused those sensational effects, according to a June 2022 story by Space.com. (It can take days for CMEs to reach Earth.)
“For these very large/fast CMEs, the time from detection of the eruption/flare to arrival of the CME can be as short as 14 hours,” Berger told Apogee.
Studies have determined that the landmark event was twice the size of any other solar storm in the past 500 years, History.com reported in August 2023.
According to a 2008 report from the National Academy of Sciences, a similar storm now could cause “extensive social and economic disruptions” by affecting power grids, satellite communications and GPS systems, according to History.com, which estimated that such a global upheaval could cost as much as $2 trillion. By contrast, a 1989 storm that caused disruptions to power grids ranging from the Canadian province of Quebec to San Francisco had an estimated cost of more than $2 billion, according to the website SolarStorms.org.
“During a really, really large geomagnetic storm, your power grid may go unstable and result in a blackout, particularly in the northeast of the U.S. and Minnesota, which are the regions most susceptible to ground currents during geomagnetic storms,” Berger said.
U.S. space missions
The CME that affected the mines in Vietnamese waters occurred in the months between the Apollo 16 and 17 missions in 1972.
“Such eruptions in the past have caused very large radiation storms that would have very serious consequences — up to and including death — for astronauts in deep space,” Berger said.
Indeed, scientists determined that had U.S. astronauts been on the surface of the moon or orbiting it, they would have received a near-lethal radiation dose, according to the Johns Hopkins University Applied Physics Laboratory (APL). If there had been a mission in August, the crew aboard the Apollo command module would have been protected from all but 10% of the incoming radiation. Still, even such a reduced dose “could have caused acute radiation sickness if the astronauts were located outside the protective magnetic field of Earth, which was the case for much of a lunar mission,” according to APL. If astronauts had been taking part in an EVA, or extravehicular activity, while in orbit or on the moon, they could have suffered from severe radiation poisoning, APL said. The astronauts would also have been at an increased cancer risk. The storm was one of only a handful that have occurred in the Space Age that could cause severe illness and was potentially the most hazardous, according to APL.
“Had the most intense solar activity of early August occurred during a mission, it would have forced the crew to abort the flight and resort to contingency measures, including an emergency return and landing for medical treatment,” APL concluded.
Humans are not the only ones at risk from solar activity.
“The energetic protons emitted from the sun during large flares can degrade solar panels on spacecraft in orbit or in deep space,” Berger said.
Solar activity such as geomagnetic storms can also affect the ability of spacecraft to maintain orbit.
“When a large coronal mass ejection hits the Earth and causes a geomagnetic storm, the electrical currents in the ionosphere cause heating” that can interfere with spacecraft, Berger said.
A prominent example came in 1979 when the dormant Skylab space station reentered Earth’s atmosphere much sooner than NASA had forecast because of higher-than-expected solar activity. The conditions caused Earth’s atmosphere to expand, increasing drag on the large spacecraft and causing its orbit to decay. On July 11, 1979, the 76,657-kilogram Skylab burned up in the atmosphere with debris landing over Australia and the Indian Ocean.
In 2022, a geomagnetic storm — “rather weak,” according to APL — caused the destruction of dozens of Starlink satellites a day after their SpaceX launch. Again, “atmospheric drag” caused by a warming atmosphere played a role, preventing the satellites from reaching a stable orbit.
That interference can also extend to the tools used to forecast space weather.
“Those same energetic protons from large solar eruptions can blind the coronagraph telescopes that we use to see the CMEs coming toward Earth,” Berger said. “Also, they can swamp star trackers and cause some satellites to go into safe mode temporarily.”
More data
With the ever-increasing number of satellites in Earth orbit — 11,000 active ones — forecasters are looking to space research missions to give them more insight into the sun and its effects on Earth.
NASA’s Parker Solar Probe passed closer to the sun than any spacecraft in history in December 2024, and there are two upcoming missions — the Multi-slit Solar Explorer, or MUSE (2027) and HelioSwarm (2029) — that NASA expects will improve the understanding of the sun’s dynamics.
“These missions will … offer critical information to help protect astronauts, satellites, and communications signals such as GPS,” according to NASA.
Berger said that MUSE could yield forecast benefits.
“MUSE will observe the solar chromosphere, where we believe that solar flares are triggered and may give us new insights that can help predict when eruptions/flares will occur,” he said. “Currently we have no reliable methods for predicting solar flares ahead of time — NOAA just issues alerts once the X-rays are detected.”
NOAA is the U.S. government’s official forecast source through its Space Weather Prediction Center (SWPC). The SWPC office uses a range of terrestrial and space-based systems to monitor the solar atmosphere. The SWPC’s forecasts are used by militaries, institutions and industries around the world.
“I would say that the sun is responsible for 95% of the aggravation that the Department of Defense and civilian colleagues feel in terms of space impacts,” Knipp, the University of Colorado researcher, said in an April 2024 news release from the U.S. Military Academy.
As Operation Anaconda demonstrated, improvements in forecasting space weather — and its impacts — can help save lives.