Sun's magnetic field controls heliosphere's shape much more than previously thought

A new study of the solar system suggests that astrophysical jets are driven by the sun.

Washington: A new study of the solar system suggests that astrophysical jets are driven by the sun.

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

For decades, scientists have visualized the heliosphere as shaped like a comet, with a very long tail extending thousands of times as far as the distance from the Earth to the sun.

Lead author Merav Opher of Boston University said that new research suggests that the sun's magnetic field controls the large-scale shape of the heliosphere much more than had been previously thought.

In the new model, the magnetic field squeezes the solar wind along the sun's North and South axes, producing two jets that are then dragged downstream by the flow of the interstellar medium through which the heliosphere moves.

The model, which indicates that the heliospheric tail doesn't extend to large distances but is split into two by the two jets and that the format of the jets is similar to that of astrophysical jets observed in many other stars and around black holes, shows that tension of the magnetic field controls what happens to the solar wind in the tail.

Co-author James Drake of the University of Maryland added that jets are really important in astrophysics and from what they can tell, the mechanism that's driving these heliospheric jets is basically the same as it is in, for example, the Crab Nebula.

Opher added that it's also exciting that these jets are very turbulent, and will be very good particle accelerators and the jets might, for example, play a role in the acceleration of so-called anomalous cosmic rays. They don't know where these particles are accelerated; it's a bit of a puzzle.

Solving such puzzles will be important for space travel. The heliosphere acts as a cocoon to protect us, by filtering galactic cosmic rays and understanding the physical phenomena that govern the shape of the heliosphere will help us understand the filter, she added.

The study is published in Astrophysical Journal Letters. 


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