Other
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsh43b..04f&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #SH43B-04
Other
2104 Cosmic Rays, 2114 Energetic Particles (7514), 2124 Heliopause And Solar Wind Termination, 2139 Interplanetary Shocks, 7537 Solar And Stellar Variability (1650)
Scientific paper
The Voyager 1 spacecraft crossed the termination shock (TS) and entered the heliosheath region at the end of 2004. Unexpected spectral properties of energetic particle distributions before and after the shock crossing include low-energy enhancements (TSP component) followed by a spectral slope change to a softer power law. We evaluate a series of simple one-dimensional models of shock evolution and energetic particle acceleration under the influence of large scale plasma perturbation in the solar wind. We show that the TS can attain speeds in excess of 100 km/s after a passage of rarefaction structures resulting in sunward plasma velocities in the heliosheath. Spectral properties and temporal evolution of the accelerated particle population are investigated for two scenarios involving different density or different velocity streams as upstream perturbations. We also suggest other possible mechanisms capable of reproducing the observed spectral features. Low-energy particles could be coming from a location magnetically connected to the TS, while higher energy anomalous cosmic rays are probably produced at lower latitudes and arrive modulated by means of cross-field diffusion. Spectral breaks are also possible if particle injection at the TS is intermittent, governed by the changing angle between the direction of the interplanetary magnetic field and the shock normal. Finally, double power laws could be a consequence of the presence of regions of enhanced turbulence up- and downstream of the shock that give way to regions of relatively large diffusion coefficient, thus facilitating particle escape from the acceleration region.
Florinski Vladimir
Zank Gary P.
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