NASA MAVEN finds charged-particle effect

NASA said this week that its MAVEN orbiter has detected the Zwan-Wolf effect in Mars’ ionosphere — the first time the phenomenon has been observed in a planetary atmosphere beyond Earth. The agency posted the result on May 18, saying the finding came from MAVEN measurements during a large solar storm in December 2023 and was reported in a new *Nature Communications* study led by Christopher Fowler of West Virginia University. (science.nasa.gov) The effect is a plasma process long studied at Earth, where charged particles are squeezed along magnetic structures known as flux tubes. NASA described it with a simple image: particles being pushed “like toothpaste coming out of a tube.” At Earth, the effect helps deflect the solar wind; at Mars, researchers said, it appears inside the ionosphere, below about 200 kilometers altitude, where it redistributes charged particles through the upper atmosphere. (science.nasa.gov) That matters because Mars does not have Earth’s global magnetic shield. Instead, it has an induced magnetosphere shaped by the solar wind and localized crustal magnetic fields. MAVEN’s data suggest that under storm conditions those magnetic structures can concentrate charged particles strongly enough for the Zwan-Wolf effect to become visible in the measurements. NASA said the event it analyzed was amplified by a large solar storm, and the paper says the process may be active more continuously at levels below MAVEN’s detection threshold. (science.nasa.gov) The discovery adds a new piece to MAVEN’s broader job at Mars: tracking how the planet’s upper atmosphere interacts with the solar wind and escapes to space over time. NASA says MAVEN, which entered Mars orbit on Sept. 21, 2014, is the first mission devoted to understanding the Martian upper atmosphere and how atmospheric loss helped turn Mars from a warmer, wetter world into the cold, dry planet seen today. (science.nasa.gov) Fowler said in NASA’s release that he first noticed “very interesting wiggles” in the magnetic-field data and did not expect them to be this effect because it had “never been seen in a planetary atmosphere before.” The underlying study, published May 18 in *Nature Communications*, is titled “Detection of Zwan-Wolf effect in the ionosphere of Mars” and lists researchers from West Virginia University, UC Berkeley, the University of Iowa, the University of Colorado Boulder, UCLA, the University of Leicester, CNRS and NASA Goddard among the authors. (science.nasa.gov) The next step is likely more event-by-event analysis rather than a single follow-up announcement. NASA’s release points researchers toward continued MAVEN observations of solar storms and Mars’ ionosphere, while the published paper provides the formal record and author list for the result. (science.nasa.gov)