Christopher Fowler, a WVU planetary scientist, is part of a NASA research team that analyzes data collected from Mars by the twin satellites of the MAVEN mission. (WVU Photo/Matt Sunday)
Data beamed back from Mars by the NASA spacecraft MAVEN provides the first evidence that a phenomenon protecting planets from solar winds can occur in the atmospheres of worlds that lack strong magnetic fields, according to research led by West Virginia University planetary scientist Christopher Fowler.
Fowler, a research assistant professor at the WVU Eberly College of Arts and Sciences and a member of the WVU Center for Kinetic Plasma Physics, said MAVEN’s observations advance scientists’ understanding of how the sun interacts with the solar system and especially with unmagnetized bodies like comets, Saturn’s moon Titan, Venus and Mars.
Fowler and his colleagues discovered indications of a phenomenon called the Zwan-Wolf effect in data MAVEN collected in December 2023, during a “coronal mass ejection event” in which huge magnetic clouds of electrified gas called plasma exploded from the sun and spread through the solar system, causing solar storms and electromagnetic disturbances.
Their findings appear in Nature Communications.
When solar wind, the continuous flow of plasma emitted by the sun, encounters bodies such as planets and comets, it is deflected around them, much like the flow of water in a stream is deflected around a rock, Fowler explained.
“However,” he added, “because the water in that stream is relatively dense, physical collisions between water molecules bumping into each other and the rock determine how the water is diverted. In contrast, the environment in space is so tenuous that solar wind particles do not bump into each other. Instead, electromagnetic forces control how particles are deflected around these bodies.”
If the solar wind meets and curves around a planet that has a strong magnetic field, like Earth, that’s when the Zwan-Wolf effect plays a role, contributing to those electromagnetic forces by squeezing the plasma through “magnetic flux tubes” — regions of space created by bundles of parallel magnetic field lines.
“The squeezing helps move the solar wind plasma around the planet, and it makes the plasma less dense in front of the planet,” Fowler said.
“By finding this effect in the atmosphere of Mars, we are discovering new ways in which our sun can interact with and affect planets in our solar system. It’s amazing to think that an eruption on the sun can disturb the atmosphere of Mars 142 million miles away.”
Before Fowler noticed what he called “very interesting wiggles” in the observations from MAVEN, scientists believed the Zwan-Wolf effect only happened in the region above a planet’s atmosphere, known as the magnetosphere.
What Fowler’s research group discovered in the data from the 2023 solar storm was the first evidence of the Zwan-Wolf effect happening not in a planetary magnetosphere, but in Mars’ atmosphere.
“We think this effect could occur in the Martian atmosphere all the time, but it’s usually such a small effect that our instruments aren’t sensitive enough to detect it,” Fowler said.
“The solar storm really hit Mars hard and disturbed the entire space environment around the planet. This seems to have amplified the Zwan-Wolf effect so that we could observe it during this time period. We got lucky, being in the right place at the right time with MAVEN to see this.”
Questions remain, he added, including how far down into the Martian atmosphere the Zwan-Wolf effect can reach.
“We observed these signatures all the way down to the lowest altitudes that MAVEN sampled, suggesting that it impacted the atmosphere even below the spacecraft,” Fowler said. “Understanding how these space weather events impact our solar system is important, not only for keeping our robotic — and potentially, human — explorers safe in the future, but for protecting the space assets that we rely on for our everyday technology here on Earth.”
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mm/5/28/26
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