Evolution of the Energy Spectra of Anomalous Cosmic Rays at Voyager 1 and 2 in the Outer Heliosphere
Abstract
As of 2 March 2008, the Voyager 1 (V1) spacecraft was at 105.5 AU and 34.3 deg N. It is in the heliosheath, presumably ~12 AU beyond the solar wind termination shock (TS). The Voyager 2 (V2) spacecraft is at 85.2 AU and 27.8 deg S. It also is in the heliosheath, having crossed the TS several times from 30 August to 1 September 2007. The energy spectra of anomalous cosmic ray (ACR) He at V2 has a modulated shape, indicating that it is not near the source of ACRs. The energy spectrum of ACR He at V1 is much less modulated and still evolving at ~3-10 MeV/nuc, indicating that V1 has not yet observed the source intensity of ACRs at these energies. The intensity vs time profiles indicate transient variations are occurring, making the determination of spatial gradients challenging. We will present the latest observations at the meeting and compare with predictions of competing theoretical models for the origin and acceleration of ACRs. This work was supported by NASA under contract NAS7-03001.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2008
- Bibcode:
- 2008AGUSMSH24A..04C
- Keywords:
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- 2104 Cosmic rays;
- 2114 Energetic particles (7514);
- 2124 Heliopause and solar wind termination;
- 2126 Heliosphere/interstellar medium interactions