The NASA/ESA Solar Orbiter has recently captured the highest ever observed level of a scarce helium isotope. 3 The emission originated from the Sun. An interdisciplinary team led by the Southwest Research Institute aimed to uncover the origin of this peculiar event to gain deeper insights into the processes driving solar energetic particles (SEPs), which populate our solar system. These SEPs consist of high-speed, energized particles such as protons, electrons, and heavy ions, often linked to phenomena like solar flares and coronal mass ejections.
This particular isotope, which is less heavy than the more prevalent one, 4 He differs by just one neutron and is extremely rare in our solar system—found at a ratio of approximately one. 3 He ion per 2,500 4 "He noted, 'Ions,' stated Dr. Radoslav Bucik from SwRI, who led the study documented in a research paper. However, solar jets seem to selectively speed up protons,'" he added. 3 He reaches high velocities or energies, probably because of its distinct charge-to-mass ratio.
Bucic stated that the mechanism causing this acceleration is still unknown, but it generally has the potential to enhance 3 The presence was increased by up to 10,000 times its typical concentration in the Sun's atmosphere—a phenomenon unmatched in any other recognized astrophysical environment. Astonishingly, Solar Orbiter detected a 200,000-fold amplification in this instance. 3 He. Besides its plentiful availability, the 3 He reached much faster velocities compared to heavier components.
Published in The Astrophysical Journal , the SwRI team identified the source of the 3 NASA's Solar Dynamics Observatory (SDO) captured detailed imagery of a minor solar jet near the boundary of a coronal hole—an area where magnetic fields extend outward toward interstellar space. Even though this jet was quite small, it showed clear connections to the SEP event, according to Bucik.
"He noted that unexpectedly, the magnetic field strength in this area was quite weak, more characteristic of calm solar zones instead of active ones." This discovery backs up previous hypotheses indicating that 3 Enrichment occurs more frequently in weakly magnetized plasma environments with minimal turbulence.
Moreover, this occurrence distinguishes itself as one of the few instances where ion enhancements deviate from the typical trend. Generally, phenomena akin to this show an elevated presence of heavier ions including iron. However, in this particular instance, iron levels did not rise. Rather, elements such as carbon, nitrogen, silicon, and sulfur were notably more prevalent than anticipated. Researchers have documented merely 19 comparable occurrences over the last quarter-century, underscoring both the infrequency and enigmatic character of this event.
When the Parker Solar Probe was at an advantageous position, it was still too distant to capture the occurrence, as noted by Bucik. This underscores the necessity of having spacecraft nearer to the Sun to observe more of such minor yet fascinating phenomena, thereby providing crucial information about the processes behind the acceleration of what remains one of the least comprehended groups of high-energy particles in our solar system.
More information: Radoslav Bučík and colleagues explored the unusual composition origin. 3 He-rich Solar Energetic Particles, The Astrophysical Journal (2025). DOI: 10.3847/1538-4357/adb48d
Furnished by Southwest Research Institute
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