SEPs are charged particles accelerated during solar phenomena such as flares and coronal mass ejections. Among them, 3He is exceptionally rare, typically appearing at a ratio of one per 2,500 helium-4 (4He) atoms in the solar environment. Yet, according to Dr. Radoslav Bucik of SwRI, "This rare isotope, which is lighter than the more common 4He by just one neutron, is scarce in our solar system - found at a ratio of about one 3He ion per 2,500 4He ions." What sets this event apart is the staggering enrichment: a 200,000-fold increase in 3He levels.
This dramatic enhancement far surpasses the 10,000-fold boosts seen in earlier events, and it wasn't just the quantity of 3He that stood out. The particles were also accelerated to speeds much higher than typically observed, exceeding those of even heavier solar elements.
By analyzing data from NASA's Solar Dynamics Observatory (SDO), the SwRI team identified the precise source: a small solar jet situated on the boundary of a coronal hole. These holes are known for their open magnetic field lines, which allow particles to escape into space. Despite the jet's modest size, its connection to the particle surge was unmistakable.
"Surprisingly, the magnetic field strength in this region was weak, more typical of quiet solar areas rather than active regions," Bucik explained. "This finding supports earlier theories suggesting that 3He enrichment is more likely in weakly magnetized plasma, where turbulence is minimal."
Adding to the mystery, the usual pattern of heavy ion enhancement did not occur. While SEPs often show elevated levels of heavy elements like iron, this event featured higher-than-expected concentrations of carbon, nitrogen, silicon, and sulfur, but not iron. Such anomalies have only been documented 19 times in the past quarter-century.
Although NASA's Parker Solar Probe was optimally located to observe the Sun, it was too distant to register this particular occurrence. Bucik noted this emphasizes the need for missions that can operate closer to the Sun, capturing these subtle but scientifically valuable events. Such data may unlock the processes behind the acceleration of one of the least understood classes of solar particles.
Research Report:Origin of unusual composition of 3He-rich solar energetic particles
Related Links
Southwest Research Institute
Solar Science News at SpaceDaily
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