Solar Orbiter Detects Record Helium-3 Concentration in Solar Wind, Shedding Light on Particle Acceleration

The Solar Orbiter, a joint mission by NASA and the European Space Agency, has recently detected an unprecedented concentration of the rare helium-3 isotope in the solar wind. According to a Southwest Research Institute (SwRI)-led team, this discovery offers valuable insights into the acceleration mechanisms of solar energetic particles (SEPs). Helium-3 is scarce in the Solar System, with a typical ratio to helium-4 of approximately 1 to 2,500. However, in this instance, the Solar Orbiter recorded a 200,000-fold increase compared to normal levels. These particles were accelerated to significantly higher speeds than heavier elements. The event originated from a small solar jet at the edge of a coronal hole, a region characterized by open magnetic field lines. Observations indicated that the magnetic field in this area was unusually weak for active solar regions, which supports the theory of preferential acceleration of helium-3 in weakly magnetized plasma. In addition, the instruments registered anomalously high levels of carbon, nitrogen, neon, and sulfur, instead of an increase in heavy ions like iron. Dr. Radoslav Bucik, lead author of the study, noted that solar jets appear to preferentially accelerate helium-3 due to its unique charge-to-mass ratio. The mechanism behind this acceleration is still unknown. Over the past 25 years, only 19 similar events have been observed, making this recent discovery particularly significant.