Source: AGU Advances

The Sun continuously blasts charged, magnetic field–carrying particles, or plasma, in all directions. This solar wind interacts with the magnetic fields and atmospheres of several of our solar system’s planets and other bodies, sculpting long magnetic tails of charged particles—magnetotails—that stretch into space behind them.

Magnetotails contain thin layers of electric current–carrying plasma sheets, which sometimes “flap” in an up-and-down waving motion. Spacecraft observations have revealed that flapping in Earth’s magnetotail can be driven by a process called magnetic reconnection, in which magnetic field lines rapidly break and then snap together in a new configuration, releasing stored energy. However, whether reconnection plays this same role beyond Earth has thus far been a mystery.

Wen et al. report the first evidence that magnetic reconnection may also trigger magnetotail flapping at Mars.

Unlike Earth, Mars lost its global magnetic field billions of years ago. But it still sports a magnetotail, thanks in large part to interactions between the solar wind and charged particles in its upper atmosphere. Strong magnetic fields embedded in certain patches of the Martian crust—remnants of its lost planet-wide field—also influence the magnetotail.

Until recently, Mars’s magnetotail could only be studied using observations from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. MAVEN showed that the Martian magnetotail is highly dynamic, with a structure that twists, shifts, and flaps—and from which charged particles may escape into space. But because MAVEN can observe only one part of the magnetotail at a time, it couldn’t identify what processes might trigger flapping.

Another spacecraft, China’s Tianwen-1 orbiter, has now provided a second set of eyes. The researchers analyzed simultaneous observations from the two spacecraft, finding that signatures of magnetic reconnection detected by MAVEN in the upstream part of the magnetotail tended to coincide with flapping events detected downstream by Tianwen-1.

Before or during flapping, the spacecraft also detected temporary, twisted plasma structures known as flux ropes. A similar link has previously been observed on Earth, and it suggests that flux ropes generated by magnetic reconnection upstream might propagate downstream, driving instabilities in the magnetotail’s plasma sheets and triggering flapping.

Though more research is needed to confirm these findings, they shed new light on how energy moves and is released in space around Mars—and possibly other planets and celestial objects. (AGU Advances, https://doi.org/10.1029/2026AV002343, 2026)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2026), What makes Mars’s magnetotail flap?, Eos, 107, https://doi.org/10.1029/2026EO260123. Published on 20 April 2026.

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Source: Journal of Geophysical Research: Solid Earth

Magnetic rocks with iron oxide concentrations act as natural chroniclers of Earth’s past continental movements. Using small samples of rocks, scientists can isolate magnetic grains that were frozen in orientation as the rock solidified. The magnetization of these grains acts as a miniature compass needle, pointing toward ancient magnetic poles. This same principle applies to extraterrestrial samples, such as meteorites and lunar rocks, which preserve evidence of the early solar nebula’s evolution.

However, traditional bottle cap–sized bulk samples often contain a mixture of reliable and unreliable magnetic signals, resulting in complex data that hamper interpretation. To improve accuracy, researchers have turned to magnetic microscopy. This technique maps magnetic fields at submillimeter to submicrometer scales in thinly sliced rock sections using advanced tools like a quantum diamond microscope (QDM) or a cryogenic superconducting quantum interference device microscope. By creating high-resolution maps of individual magnetic particles, scientists can reconstruct ancient fields with much higher precision while filtering out muddy signals from unstable grains.

Despite its potential, magnetic microscopy is an emerging field with its own set of uncertainties. To help constrain measurement data, Bellon et al. combined QDM observations with computer modeling to analyze how a magnetic particle’s stray field—the magnetic flux that leaks into the surrounding space—decays as it moves away from the source. They specifically investigated how a particle’s internal magnetic structure and external measurement noise affect the accuracy of these reconstructions.

The study found that in iron oxides, the smallest and most magnetically stable particles produce signals that are strong at the source but fade rapidly with distance. In contrast, larger particles produce signals that remain detectable farther away. This creates a challenge: The most stable grains for long-term geological data (the smallest ones) are the hardest to detect if the sensor is not perfectly positioned or if sensor interference is present.

By quantifying measurement error, the authors provide a road map for the field of micropaleomagnetism. Their findings could allow researchers to better account for uncertainty, leading to more robust reconstructions of Earth’s magnetic history and a deeper understanding of planetary evolution. (Journal of Geophysical Research: Solid Earth, https://doi.org/10.1029/2025JB033133, 2026)

—Aaron Sidder, Science Writer

Citation: Sidder, A. (2026), Navigating the past with ancient stone compass needles, Eos, 107, https://doi.org/10.1029/2026EO260122. Published on 16 April 2026.

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Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: AGU Advances

Solar eruptions can trigger geomagnetic storms that disrupt satellites, GPS, and power grids, affecting daily activities and technology. Therefore, it is extremely important to understand these storms in order to mitigate their impact. Previous studies mainly focused on interplanetary conditions.

Ghag et al. [2026] investigate the interaction between solar ultraviolet light (EUV) during storms and the Earth magnetic field, taking into account its misalignment and offset with respect to the Earth’s rotational axis, which depend on time. Such misalignment and offset induce variations in EUV exposure in turn influencing the ionosphere and its interaction with the magnetosphere.

The study applies the Multiscale Atmosphere-Geospace Environment (MAGE), a physics based fully coupled whole geospace model. The causal relationship between storm timing and storm effect is explored revealing insights on our capability to predict storm impact based on the time dependent Earth system state.

Citation: Ghag, K., Lotko, W., Pham, K., Lin, D., Merkin, V., Raghav, A., & Wiltberger, M. (2026). Universal time influence on stormtime magnetosphere ionosphere coupling. AGU Advances, 7, e2025AV002071. https://doi.org/10.1029/2025AV002071

—Alberto Montanari, Editor-in-Chief, AGU Advances

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.