Observations of the Interstellar Magnetic Field in the Outer Heliosheath: Voyager 1
Abstract
New observations of the magnetic field {\boldsymbol{B}} from ≈2014.7 through 2016.3288, together with the previous observations dating back to 2012 August 25, show that Voyager 1 continued to observe draped interstellar magnetic fields in the outer heliosheath. During this time, the direction of {\boldsymbol{B}} was nearly constant (±3°), with no significant long-term trend. The slope of a linear least squares fit to the variation of the magnetic field strength B with time is (0.001 ± 0.001) nT yr-1, consistent with no net change, and the average B = (0.48 ± 0.04) nT. The new observations show a second “disturbed interval” in which B was ≤slant 1.2< B> for ≈267 days. This interval began with a weak shock on 2014/236 (2014.6438), contained oscillations in B with a 28 day period, and possibly ended with a pressure balanced structure or a reverse shock. It is likely this disturbed interval was associated with Sun/solar wind disturbances that impacted the heliopause and produced disturbances that propagated into the outer heliosheath. A quiet interval containing weaker less variable {\boldsymbol{B}} was observed from ≈2015.3700 until at least 2016.0. Unlike the previous quiet interval observed in the outer heliosheath, the direction of {\boldsymbol{B}} did not change linearly and could not be extrapolated to the center of the IBEX ribbon.
- Publication:
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The Astrophysical Journal
- Pub Date:
- October 2016
- DOI:
- 10.3847/0004-637X/829/2/134
- Bibcode:
- 2016ApJ...829..134B
- Keywords:
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- ISM: magnetic fields;
- Sun: heliosphere