科研之友
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摘要
Taken together, the Voyager 1 and 2 (VI and V2) spacecraft have collected over 11 yr of data in the heliosheath. Despite extensive study, energetic particles and magnetic fields measured in the heliosheath have not been reconciled by existing models. In particular, the differences between the energetic particle intensity variations at V1 and V2 are unexplained. While energetic particle intensities at Vi change gradually over 7 yr in the heliosheath, those at V2 vary by a factor similar to 10 in 1 yr. Energetic particle intensities at V2 show temporally coherent variations over a broad range of species and energies: from suprathermal ions (10s of keV) to galactic cosmic rays (> 1 GeV), as well as electrons from 10s of keV to > 100 MeV, corresponding to a range similar to 10(4) in particle gyroradii. Here we suggest that many of the intensity variations of energetic particle populations in the heliosheath are organized by their proximity to two fundamentally different regions- the unipolar heliosheath (UHS) and the sectored heliosheath (SHS). The SHS is a region of enhanced particle intensities, wherein particle transport, acceleration, and magnetic connectivity differ from those in the UHS. The SHS may serve as either a reservoir of energetic particles or as a region of enhanced transport, depending on the particle species and energy. Comparatively, particle intensities in the UHS are greatly reduced. We propose that the boundary between the SHS and UHS plays as important a role in the physics of heliosheath particles and fields as do the termination shock and heliopause.
- 出版日期2014-2-1
