Research sheds light on solar wind dynamics
Scientists at the Southwest Research Institute have used measurements from the New Horizons spacecraft to study changes in the solar wind as it travels through the outer heliosphere. Published in the Astrophysical Journal, the study reveals that interstellar atoms exert a measurable drag on the stream of charged particles emitted by the Sun.
Observations far from the Sun
Since its Pluto flyby in 2015, New Horizons has continuously recorded particle density, speed and temperature of the solar wind out to more than 120 astronomical units. Analyzing this long‑term dataset allowed researchers to quantify a gradual decline in wind velocity.
Role of neutral interstellar atoms
The team found that neutral atoms from the interstellar medium infiltrate the solar system and collide with the charged particles of the solar wind. These interactions cause the wind to lose energy, manifesting as a slowdown.
Implications for the heliospheric boundary
The findings provide crucial insight into the physical processes at the interface between the solar wind and interstellar space. The deceleration influences the shape and location of the heliosphere, which shields the solar system from galactic radiation.
Future work
Continued observations by New Horizons and complementary missions aim to refine our understanding of solar‑wind–interstellar‑medium interactions and improve models of heliospheric structure.