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Published May 1, 2012 | Published
Journal Article Open

Radial Velocity along the Voyager 1 Trajectory: The Effect of Solar Cycle

Abstract

As Voyager 1 and Voyager 2 are approaching the heliopause (HP)—the boundary between the solar wind (SW) and the local interstellar medium (LISM)—we expect new, unknown features of the heliospheric interface to be revealed. A seeming puzzle reported recently by Krimigis et al. concerns the unusually low, even negative, radial velocity components derived from the energetic ion distribution. Steady-state plasma models of the inner heliosheath (IHS) show that the radial velocity should not be equal to zero even at the surface of the HP. Here we demonstrate that the velocity distributions observed by Voyager 1 are consistent with time-dependent simulations of the SW-LISM interaction. In this Letter, we analyze the results from a numerical model of the large-scale heliosphere that includes solar cycle effects. Our simulations show that prolonged periods of low to negative radial velocity can exist in the IHS at substantial distances from the HP. It is also shown that Voyager 1 was more likely to observe such regions than Voyager 2.

Additional Information

© 2012 American Astronomical Society. Received 2012 January 19; accepted 2012 March 14; published 2012 April 9. The authors are grateful to S. T. Suess for valuable comments. This work is supported by NASA grants NNX08AJ21G, NNX08AE41G, NNX09AW44G, NNH09AG62G, NNH09AM47I, NNX09AP74A, NNX09AG63G, NNX10AE46G, NNX12AB30G, and NASA contract NNN06AA01C. Supercomputer time allocations were provided on SGI Pleiades by NASA High-End Computing Program award SMD-10-1691, Cray XT5 Kraken by NSF XSEDE project MCA07S033, and on Cray XT5 Jaguar by ORNL Director Discretion project PSS0006. This work was also supported by the IBEX mission as a part of NASA's Explorer program.

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August 22, 2023
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