solarorbiter

Within the Sun’s polar region, those thin “feathery” structures conceal a host of high-frequency magnetic waves that were previously almost impossible to capture.

Researchers from Peking University—Yu Hang Gao and Hui Tian’s team—used Solar Orbiter’s Extreme Ultraviolet Imager (EUI) to closely observe the plume-like feathery structures in polar coronal holes in the northern hemisphere. EUI captures an image about every 5 seconds, with a spatial resolution of roughly 420 km per pixel; compared with the commonly used SDO/AIA (about every 12 seconds, about 1100 km per pixel), it is both faster and finer.

Running the same automated wave-tracking program (NUWT), EUI detected about 2,318 oscillation events, while SDO detected only about 560. In the EUI data, more than one-third of the periods are shorter than 100 seconds; the corresponding fraction in SDO is only about 9%. The average transverse velocity of the plasma threads is also higher—about 15.4 km/s versus 9.9 km/s. Based on the estimates in the paper, the energy flux is about 2.6 times higher than the earlier, lower-resolution estimate.

Could these high-frequency magnetohydrodynamic waves help out? The outer corona is often more than a million degrees Celsius, and the fast solar wind still needs to be accelerated outward—where the energy comes from has been a long-standing question. This observational study at least makes it clearer that “a large portion of the high-frequency wave energy in polar feathery structures has been underestimated.” The observing window was 2021-09-14; the paper was published in National Science Review (DOI 10.1093/nsr/nwag370).

Figure illustrates Solar Orbiter/EUI polar plume structures and transverse wave oscillations. Public coverage can be found on Phys.org (2026-09-21), and in a Science China Press news release via EurekAlert.

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