Time-dependent cosmic ray modulation along Voyager 1 and 2 trajectories
Abstract
A two-dimensional, time-dependent transport model is used to compute cosmic ray modulation in the inner and outer heliosphere. Results in the inner heliosphere (1 AU) are compared to IMP-8 and Ulysses observations, while for the outer heliosphere results are compared to the Voyager 1 and Voyager 2 observations. Time-dependence for the assumed transport parameters are achieved by incorporating recent theoretical advances in transport parameters by Teufel and Schlickeiser (2002), Shalchi et.al (2004) and Minnie et.al (2007). This new approach to cosmic ray modulation leads to results which are compatible to spacecraft observations in both the inner and outer heliosphere. The computations along the Voyager 1 and Voyager 2 trajectories suggest: (1) A possible asymmetry in the heliosphere since the observations cannot be fitted with the same set of transport parameters. (2) Alternatively, a symmetric heliosphere but with different transport parameters in the northern and southern hemispheres. A range of different but plausible local interstellar spectra and heliopause position are investigated, considering that recent Voyager 1 observations suggest that this spacecraft is about to enter the interstellar medium, and perhaps crossing the heliospheric modulation boundary.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.1181M