Characteristics of the Termination Shock: Insights from Voyager
We examine the energy spectra obtained from the cosmic ray instrument on the Voyager 1 spacecraft during 2002/215 through 2005/60. We find that the energy spectra of protons below ~20 MeV often resemble two power laws with a relatively hard index at low energies and a softer index at higher energies. The point of intersection of the two power laws is ~3 MeV. Beginning in 2005, the low-energy index is typically –1.5, corresponding to a shock strength (compression ratio) of 2.5. We attribute these characteristics to a restricted region of the solar wind termination shock that is sporadically connected to the Voyager 1 spacecraft by the interplanetary magnetic field. The absence of significant spectral variability in 2005 suggests that Voyager 1 entered a region with minimal spatial gradients of the lowest energy ions.
Additional Information©2005 American Institute of Physics. Issue Date: 1 August 2005. This work was supported by NASA under contract NAS7-03001. # 96.50.Fm Interplanetary shock waves # 96.60.Vg Solar particle radiation, solar wind, and solar neutrinos # 96.40.De Cosmic ray composition, energy spectra, and interactions # 96.50.Bh Solar and interplanetary electric and magnetic fields (including solar wind fields) # 07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
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