This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A team of researchers led by the National Astronomical Observatory of Japan discovered unexpectedly intricate magnetic structures above quiet-sun regions by observing the sun with the balloon-borne solar observatory Sunrise-III during its 2024 flight in Earth's stratosphere. The work is published in The Astrophysical Journal Letters.
Sunrise-III observations revealed thin, elongated, thread-like magnetic structures embedded within the magnetic canopy above a quiet-sun region. The magnetic canopy forms in the solar atmosphere (chromosphere) as magnetic fields concentrated at the solar surface (photosphere) arc outward with increasing altitude, creating an arch of magnetic structures. The new observations show that this canopy is not a simple, uniformly expanding structure but instead contains numerous thin, elongated magnetic substructures.
A numerical simulation reproduced the thread-like structures seen by Sunrise-III and showed that they are associated with magnetic field lines twisted by motions at the solar surface. In separate observations of a quiet-sun region near the solar limb (visible edge of the sun), Sunrise-III mapped the magnetic fields of spicules, jet-like structures extending upward from the solar surface, and revealed how the distribution of the magnetic field varies with height above the limb. Regions of the sun without activity such as sunspots are referred to as "quiet." Quiet-sun regions cover most of the solar surface.
The magnetic fields in quiet-sun regions are weaker than in active regions, making detailed measurements difficult for ground-based telescopes because of blurring caused by Earth's atmosphere. Sunrise-III is an international collaborative project that observes the sun with a 1-meter (3.3-foot) telescope carried by a balloon floating in the stratosphere at an altitude of 35 km (22 miles). At this altitude, the sun can be observed with very little atmospheric blurring.
The gondola carried three instruments developed by different countries. Among them, the near-infrared spectropolarimeter SCIP (Sunrise Chromospheric Infrared spectroPolarimeter), developed under NAOJ's leadership, can continuously observe the magnetic field from the photosphere up through the chromosphere. The high-precision observations from the stratosphere made it possible to map the structure of the chromospheric magnetic field above quiet-sun regions in fine detail.
These findings provide important clues to understanding how energy is transported up from the solar surface to heat the solar atmosphere. Masahito Kubo et al, Three-dimensional Magnetic Field Structure of a Quiet-Sun Region Revealed by SUNRISE III/SCIP, The Astrophysical Journal Letters (2026). DOI: 10.3847/2041-8213/ae909b Journal information: Astrophysical Journal Letters Provided by National Institutes of Natural Sciences BSc Life Sciences & Ecology.
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