Voyager 1 in the Foreshock, Termination Shock, and Heliosheath

• DOI: 10.1126/science.1117569
• Publication Date: 2005-09-22T20:58:23Z
• Authors: R. B. Decker; S. M. Krimigis; E. C. Roelof; M. E. Hill; T. P. Armstrong; G. Gloeckler; D. C. Hamilton; L. J. Lanzerotti
• Keywords: Heliosphere

Voyager 1 (V1) began measuring precursor energetic ions and electrons from the heliospheric termination shock (TS) in July 2002. During ensuing 2.5 years, average particle intensities rose as V1 penetrated deeper into foreshock of TS. Throughout 2004, observed even larger, fluctuating 40 kiloelectron volts (keV) to >/=50 megaelectron per nucleon >26 keV >/=350 keV. On day 350 2004 (2004/350), an intensity spike that was followed by a sustained factor 10 increase at lowest energies lesser increases higher energies, larger than any since 15 astronomical units 1982. The estimated solar wind radial flow speed positive (outward) approximately +100 kilometers second (km s(-1)) 2004/352 until 2005/018, when flows became predominantly negative (sunward) fluctuated between -50 0 km s(-1) about 2005/110; they then more positive, with recent values (2005/179) +50 s(-1). proton spectrum averaged over postshock period is apparently dominated strongly heated interstellar pickup ions. We interpret these observations evidence crossed TS on 2004/351 (during tracking gap) 94.0 units, evidently moving radially inward response decreasing ram pressure, has remained heliosheath least mid-2005.