Voyager 1 Finds Mayhem in the Heliopause

The main goal of the Voyager 1 mission is to discover and analyze the heliopause, the boundary beyond which the solar wind no longer blows. In other words, the spacecraft has to find out where our solar system ends and the interstellar medium begins, and this objective may have been achieved.

According to NASA, the space probe managed to move into the heliosheath back in 2004. This means that it became the first man-made object ever to explore the area of our solar system where the Sun's magnetic influence begins to dwindle and decline.

In its investigations of the heliopause, Voyager 1 found what NASA experts plastically refer to as mayhem. At this point, the spacecraft is located in a very peculiar region, where the speed of plasma originating from our parent star is zero.

This means that the probe can detect no movements of hot ionized gas at its location. Experts suspect that this happens because the solar winds have changed their orientation, not because the prove exited the solar system, Universe Today reports.

One explanation for why these winds may have turned sideways is that the interstellar medium also contains winds, which influenced the plasma streams our Sun emits, and changed their course.

“The solar wind has turned the corner. Voyager 1 is getting close to interstellar space,” explains expert Ed Stone, who is a project scientist for the Voyager mission. He is based at the California Institute of Technology (Caltech), in Pasadena.

The space probe is now roaming the heliosheath, the area where influences from the Sun are balanced out by influences from outside the solar system. These interactions are causing magnetic mayhem in this region, as evidenced by the readings Voyager 1 sends back.

The heliosheath starts some 8.7 billion miles (14 billion kilometers) from the Sun, and is anywhere between 1.5 to 15 billion kilometers (930 million to 9.3 billion miles) thick, solar physicists explain.

While flying through it, the space probe measured numerous changes in the surrounding magnetic field. All the variations were sudden and extremely pronounced, and they were produced by so-called current sheets. New Voyager data indicate that there are three types of such sheets.

The conclusion belongs to a study conducted by experts at the NASA Goddard Space Flight Center (GSFC) Geospace Physics Laboratory, who were led by scientist L. F. Burlaga. Institute for Astrophysics and Computational Sciences expert N. F. Ness also contributed to the work.

“The structures, appearing as proton boundary layers (PBL), magnetic holes or humps, or sector boundaries, were identified by characteristic fluctuations in either magnetic field strength or direction as the spacecraft crossed nearly 500 million km (310 million mi) of heliosheath in 2009,” they say.

“PBL are defined by a rapid jump in magnetic field strength, with one observed event resulting in a doubling of the field strength in just half an hour.” the researchers write in a new paper.

“Passing through a sector boundary led to a sudden change in direction of the magnetic field. Magnetic holes saw the field strength drop to near zero before returning to the original background strength. Magnetic humps consisted of a sudden spike in strength and then a return to initial levels,” they conclude.