How the Sun's Solar Wind Punches Through the Earth's Magnetic Field

Solar wind, a stream of charged particles that blow outward from the sun, can impact Earth and satellites, interfering with magnetic fields. Now, astronomers may have found out a bit more about solar wind, answering questions as to how it might break through the Earth's magnetic field.

In order to learn a bit more about solar wind, the researchers examined data from the four European Space Agency satellites in the Cluster mission. These satellites fly in formation in the Earth's magnetic field.

When two areas with plasma and magnetic fields with different orientations collide, the magnetic fields can be "clipped off" and then "reconnected" so that the topology of the magnetic field is changed. This magnetic reconnection can give energy to eruptions on the solar surface, and can even change the energy from the solar wind so that it then creates aurora.

If two colliding regions of plasma have the same density, temperature and strength, but different orientation, of their magnetic fields, then symmetrical reconnection begins. Usually, though, when solar wind meets the environment around Earth, the two regions of plasma have different characteristics.

By examining measurements from satellites in the region where the solar wind meets the Earth's magnetic field, the scientists could understand plasma physics at the height of about 60,000 km.

"We believe that this is an important piece of the puzzle for understanding how magnetic reconnection works, how charged particles are accelerated, and how particles from different regions can be mixed with each other," said Daniel Graham, one of the researchers, in a news release. "Our detailed measurements in the Earth's magnetic field can be used to understand the physics even in fusion reactors on Earth, and in far distant regions in space that we can't reach with satellites."

The findings are published in the journal Physical Review Letters.