Mapping Mayhem Where Sun’s Magnetic Influence Wanes

When Voyager 1 passed into the heliosheath in 2004, it became the first man-made object to explore the remote edge of the Sun’s magnetic influence. The heliosheath, from 1.5 to 15 billion kilometers thick (930 million to 9.3 billion miles) and starting roughly 14 billion km (8.7 billion mi) from the Sun, is where the outgoing flows of solar wind start to be pushed back by interstellar particles and magnetic fields that are heading toward the solar system. While passing through the heliosheath, Voyager 1 experienced many sudden and drastic changes in the surrounding magnetic field driven by structures called current sheets.

Using Voyager 1’s ongoing measurements of the magnetic field, Burlaga and Ness identify three distinct types of current sheets. The structures, appearing as proton boundary layers (PBLs), 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. PBLs 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.

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. The firsthand detections made by Voyager 1 are likely to be extremely important for researchers trying to decide between current leading theories for the source and structure of current sheets.

Source: Journal of Geophysical Research-Space Physics, doi:10.1029/2010JA016309, 2011 http://dx.doi.org/10.1029/2010JA016309

Title: Current sheets in the heliosheath: Voyager 1, 2009

Authors: L. F. Burlaga: Geospace Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA; N. F. Ness: Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, D. C., USA.

Contact:
Peter Weiss
+1 (202) 777 7507
pweiss@agu.org