Our planet is constantly 'bathed' in winds emanating from a star in the center of our solar system.
We know that the particles that make up the plasma of the solar heliosphere cool down as they travel. The problem is that their temperature drops much more slowly than the models predict.
“People have been studying the solar wind since its discovery in 1959, but there are many important properties of this plasma that are still not fully understood,” says physicist Stas Boldyrev of the University of Wisconsin-Madison.
“Initially, researchers believed that the solar wind should cool very quickly as it moves away from the Sun, but satellite measurements show that when it reaches Earth, its temperature is 10 times higher than expected.”
The research team has used laboratory equipment to study moving plasma and now thinks the answer to this problem lies in electrons, which simply cannot seem to get out of the control of the sun.
For a long time it was believed that the expansion process itself obeys adiabatic laws, which means that thermal energy is not added or removed from the system. This makes the numbers nice and simple, but assumes that energy is slipping in or out of the particle stream.
Unfortunately, the electron's journey is far from easy: it is being pushed into the grip of enormous magnetic fields. This chaos leaves plenty of room for heat transfer.
Just to complicate matters further, due to their tiny mass, electrons are faster than heavier ions as they fly out of the Sun's atmosphere, leaving a largely positively charged cloud of particles.
Ultimately, the growing attraction between the two opposing charges captures the momentum of the flying electrons, pulling them back to their original line, where the magnetic fields change their paths again.
Boldyrev and his colleagues suggest that the population of trapped electrons plays an important role in how electrons distribute their thermal energy, changing typical particle velocity and temperature distributions in an unpredictable manner.
This study was published in PNAS.
Sources: Photo: NASA
