Is the Magnetic Field in the Heliosheath Sector Region and in the Outer Heliosheath Laminar?

Details Is the Magnetic Field in the Heliosheath Sector Region and in the Outer Heliosheath Laminar? Is the Magnetic Field in the Heliosheath Sector Region and in the Outer Heliosheath Laminar?

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh23d..04o&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SH23D-04

Physics

Plasma Physics

[2124] Interplanetary Physics / Heliopause And Solar Wind Termination, [2134] Interplanetary Physics / Interplanetary Magnetic Fields, [7526] Solar Physics, Astrophysics, And Astronomy / Magnetic Reconnection, [7845] Space Plasma Physics / Particle Acceleration

Scientific paper

All the current global models of the heliosphere are based on the assumption that the magnetic field in the outer heliosheath close to the heliopause is laminar. We argue that in the outer heliosheath the heliospheric magnetic field is not laminar but instead consists of nested magnetic islands. Recently, we proposed (Drake et al. 2009) that the annihilation of the ``sectored'' magnetic field within the heliosheath as it is compressed on its approach to the heliopause produces the anomalous cosmic rays (ACRs) and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densly-packed magnetic islands are produced. These magnetic islands will be convected with the ambient flows as the sector boundary is carried to higher latitudes filling the outer heliosheath. We further argue that the magnetic islands will develop upstream (but still within the heliosheath) where collisionless reconnection is unfavorable -- large perturbations of the sector structure near the heliopause will cause compressions of the current sheet upstream, triggering reconnection. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the heliopause. We present a 3D MHD simulation with unprecedent numerical resolution that captures the sector boundary. We show that due to the high pressure of the interstellar magnetic field the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We test these ideas with observations of energetic electrons, which because of their high velocity are most sensitive to the structure of the magnetic field. We suggest that within our scenario we can explain two significant anomalies in the observations of energetic electrons in the outer heliosphere: the sudden decrease in the intensity of low energy electrons (0.02-1.5MeV) from the LECP instrument on Voyager 2 in 2008 (Decker 2010); and the dramatic differences in intensity trends between Galactic Cosmic Ray Electrons (3.8-59MeV) at Voyager 1 and 2 (McDonald 2010). We argue that these observations are a consequence of Voyager 2 leaving the sector region of disordered field in mid 2008 and crossing into a region of unipolar laminar field.

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