Findings reveal more about how gaseous explosions from the sun could be dangerous to Earth

Monday, June 15, 2026

A University of Iowa-led physics team has detailed the extreme expansion of a magnetic cloud that originated from a huge, gaseous explosion on the sun.

In a new study, the researchers describe the inflated magnetic cloud as recorded by spacecraft in fortuitous, separate locations as the cloud approached Earth. During that interval - spanning some 13 million miles - the cloud expanded by a fifth of its original size during its approach to Earth, as plasma inside the super-expanded bubble heated up. The researchers termed the striking increase in size a "super expansion."

"We have assumed that magnetic clouds from interplanetary coronal mass ejections will evolve in the same way," says Shirsh Soni, postdoctoral research fellow in the Department of Physics and Astronomy at Iowa and the study's corresponding author. "In this study, we show the magnetic cloud can expand dramatically in a short period of time and space, which could have impacts to Earth that we wouldn't have known about."

A magnetic cloud is a common byproduct of coronal mass ejections, large eruptions from the sun that spew hot, magnetized plasma into space. When directed toward Earth, these solar storms can disrupt satellites, navigation systems, and power grids. Understanding how they evolve as they travel, especially toward Earth, could help with predicting space weather.

A physics team led by the University of Iowa has described a "super expanded" magnetic cloud created by a coronal mass ejection on the sun. The cloud's dimensions were captured in two intervals of relatively short time and distance by two spacecraft, Solar Orbiter and Wind. Those observations led to findings that the crescent-shaped cloud grew by a fifth of its size as it approached Earth.

In this instance, the researchers chronicled at two intervals a magnetic cloud that arose from a coronal mass ejection on Nov. 4-5, 2021. As the crescent-shaped cloud, with coiled ropes of magnetized plasma within, moved toward Earth, its shape and size were captured first by the spacecraft Solar Orbiter, at 0.84 astronomical units (AU), and later by the spacecraft Wind at 0.98 AU.

The spacecraft were on the same axis as the cloud made its way toward Earth, a serendipitous occurrence that enabled the researchers to determine how it changed.

They found it had changed a lot.

In the relatively short distance between the spacecraft's measurements, the magnetic cloud expanded by 21%, triggered by the cloud's collision with the background solar wind, the 1 million mph gusts of energy from the sun. At first, the cloud compressed as it collided with the neighboring solar wind. But then it heated up and expanded as plasma inside the cloud got three times hotter.

The researchers also found that magnetic field pressure within the cloud did not change, upending what scientists using models had reported.

Shirsh Soni

Magnetic clouds from coronal mass ejections have been observed in space, but the researchers say this is the first time one has been charted by two spacecraft on the same line and at relatively close distance to each other when the cloud passed by them. Even better, scientists knew this particular outburst from the sun had spawned a major geomagnetic storm on Earth.

"First, it's rare these two spacecraft would be aligned on a sun-Earth axis," says Soni, who specializes in solar activity and outbursts. "Then, second, for them to be aligned like that during an interplanetary coronal mass ejection is so much rarer."

As plasma within the cloud heated up, it expanded by 192 kilometers - about 119 miles - per second, versus a typical speed of between 50 to 100 kilometers per second, the study authors report.

"In a typical interplanetary coronal mass ejection, when it encounters the solar wind, it could decelerate or accelerate," Soni explains. "In this case, it expanded a lot."

The study, "Super expansion of interplanetary coronal mass ejection observed by Solar Orbiter and Wind spacecraft within 0.14 AU radial separation," was published online April 24 in the journal Monthly Notices of the Royal Astronomical Society.

David Miles, associate professor in the Department of Physics and Astronomy at Iowa, is a study co-author. Other contributing authors are Ankush Bhaskar, from the Vikram Sarabhai Space Center in India; and R. Selva Kumaran, from Amity University, in Mumbai, India.

Soni's research was funded through a previous fellowship provided by the University of Michigan.