Heliosphere Shaped by Solar Jets

The Sun is the driving force behind our planetary system.  It’s energy warms our planet, drives weather and climate patterns, and fuels the aurorae that surround our magnetic poles.  The Sun also has a much grander sphere of influence beyond the orbit of the Earth, stretching into the vast space between itself and the other members of the stellar neighbourhood.

The charged particles that are released from the Sun, called the solar wind, stretch out to 120 Astronomical Units, about 18 Billion Km.  The bubble of the Sun’s influence is known as the Heliosphere, though it is anything but a sphere.  In late 2012, the Voyager 1 spacecraft reached the Heliopause, the outer edge of the Heliosphere, where the influence of the solar wind is no longer felt.

The yellow structure shown represents the heliopause, the boundary between the Sun’s region of influence and the interstellar medium.  White lines represent the Sun’s magnetic field, and Red lines represent the magnetic field of the interstellar medium. Credit: Merav Opher

Data from Voyager 1 has offered new insights into the structure of the Heliosphere and the effect of the Sun’s magnetic field on its shape.  A new model, described in a paper published Feb. 19, 2015 in the journal Astrophysical Journal Letters, shows that the magnetic field of the Sun funnels the solar wind along our star’s North-South axis, producing two jets of solar wind particles.

The jets affect the large-scale structure of the Heliosphere, resulting in two massive tails that trail its leading edge as it moves through the interstellar medium.  The previously accepted model of the Heliosphere was that it looked like a comet, with one large tail.  With this new interpretation, giving the magnetic field of the Sun a much more significant role, the structure appears to have two tails originating from the jets.

Once Voyager 2 passes through the Heliopause, as is expected in the next year or two, we will be able to gather more data on this incredibly massive structure surrounding our solar system.  It has practical applications for future space travel, as any spacecraft that intends to pass the boundary of the Heliopause will have to endure a much larger flux of potentially damaging cosmic rays.  We are lucky to have the Heliosphere protecting us from such harmful galactic radiation.

This is science that was never even thought of for Voyager, but 38 years into the mission, an old piece of 1970s technology is still pushing the boundaries, of both our solar system and our understanding.

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