Voyager 1 Magnetic Field Strength and Direction
This graphic shows how the direction of the magnetic field in the region NASA's Voyager 1 is exploring has not changed, even though the intensity of the magnetic field has increased. Voyager scientists have been watching for a change in the direction of the magnetic field as a key indicator for arriving in interstellar space. This graphic shows why scientists do not believe Voyager 1 has reached interstellar space.
The graph starts with the 235th day of 2012, which is Aug. 22. The top graphic (red) shows how the intensity of the magnetic field jumped on Aug. 25, which is the day scientists think Voyager 1 permanently entered a new solar system region they are calling the "magnetic highway." There was no change in the longitudinal direction of the field (green) or the latitudinal direction (light blue) during that crossing or since.
Scientists refer to this new region as a "magnetic highway" because here the sun's magnetic field lines are connected to the interstellar magnetic field lines. This connection allows particles from inside the bubble of charged particles the sun blows around itself - known as the heliosphere - to zip away. It also allows particles from interstellar space to zoom in.
Image credit: NASA/JPL-Caltech/GSFC/University of Delaware