Distant space weather has become a little less mysterious with some of the first data transmitted by NASA's New Horizons spacecraft, which flew by Pluto in July and has since sped deeper into space. For instance, the spacecraft has returned three years' worth of observations on solar wind — or high-energy particles flung by the sun out into space — from a region barely explored.
These same particles, when on Earth, can sometimes have enough energy to interfere with radio communication and electronics, like in the case of solar storms or coronal mass ejections. While the planet's magnetic field often provides protection from these, these particles can sometimes be seen interacting with the atmosphere through auroras, including Northern Lights.
But these particles reach out far more distant than Earth.
Observations from Solar Wind Around Pluto (SWAP) of the Southwest Research Institute revealed that the intense flow of solar particles, produced in the inner solar system through fast and slow flows and eruptive sun events, becomes more uniform by the time the solar wind has traveled the 3 billion miles to the orbit of Pluto.
The SWAP instrument tracked interstellar pickup ions — ions created as the materials turns ionized and is "picked up" by solar wind — and speculated that they could actually be the seeds of highly energetic particles dubbed as anomalous cosmic rays, which can be a potential radiation threat to astronauts.
Two Voyager spacecraft have observed these anomalous cosmic rays believed to shape the boundaries found between the solar system and interstellar space.
"The Voyagers can't measure these seed particles, only the outcome," says NASA scientist Eric Christian, who was not involved in the study but analyzes what is known as heliosphere, the area in the solar system dominated by solar wind.
So the blank patch in the observations is being supplied with data with the New Horizons entering that region, he adds.
Dr. Heather Elliott, the study's lead author, said that SWAP was busy even while other instruments on board the New Horizons were hibernating to conserve energy on the nine-year journey to Pluto. The instrument then yielded three years of almost-continuous data that detailed the space environment.
Learning more about the origin and nature of the cosmic rays can help scientists in figuring out how to keep astronauts safe during their space missions, including long-haul ones toward Mars and far beyond.
The findings were published April 6 in the Astrophysical Journal.