Voyager Observations of the Heliospheric Interface

Abstract:

Voyager 1 found a complex transition from a quasi-stagnation region dominated by slow solar wind to a region with a plasma density forty times that observed in the heliosheath by Voyager 2 and consistent with that expected for the local interstellar medium. During the one month period following the last observed current sheet crossing at 121.3 AU on July 26, 2012, Voyager 1 observed five abrupt changes in the intensities of low energy heliospheric ions and galactic cosmic rays that were correlated with abrupt changes in the intensity but not the direction of the magnetic field.

Following the fifth intensity increase that occurred at 121.6 AU on August 25, 2012, the intensity of galactic cosmic rays has remained at the highest level yet observed, with small transient variations caused by the arrival of Merged Interaction Regions propagating outward from the sun. The plasma oscillations associated with those transients revealed that for the last two years the plasma density has been consistent with Voyager 1 having durably entered interstellar space. Differing models and interpretations that have been proposed to address the complexities of the observations will be discussed.