New insights into Sun's magnetic field

The Sun's magnetic field controls the large-scale shape of the heliosphere - the domain of the Sun - much more than expected, new research suggests.

The new model shows that the magnetic field squeezes the solar wind along the Sun's north-south axis, producing two jets.

These jets are then dragged downstream by the flow of the interstellar medium - the gases and dust that lie between star systems.

"It's also exciting that these jets are very turbulent, and will be very good particle accelerators," said Merav Opher, lead author of the study.

The jets might, for example, play a role in the acceleration of so-called anomalous cosmic rays.

The heliosphere protects the solar system by filtering galactic cosmic rays, and upon leaving this protective shell, spacecraft will be bombarded by much higher levels of damaging radiation.

"Understanding the physical phenomena that govern the shape of the heliosphere will help us understand the filter," Opher said.

As the Sun skims through the galaxy, it flings out charged particles in a stream of plasma called the solar wind. The solar wind creates a bubble, known as the heliosphere, which extends far outside the solar system.

For decades, scientists have visualised the heliosphere as comet-shaped, with a very long tail extending thousands of times farther than the distance from the Earth to the Sun.

The new model indicates that the heliospheric tail doesn't extend to large distances but is split into two jets, with a form similar to astrophysical jets observed in many other stars and around black holes.

This new understanding of the heliosphere could have implications for future attempts at interstellar travel.

"Jets are really important in astrophysics," said James Drake, professor of physics and director of the Joint Space-Science Institute at the University of Maryland.

"If we're right about all of this, it gives us a local test bed for exploring some very important physics," Drake added.

The findings appeared Astrophysical Journal Letters.