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No Stagnation Region before the Heliopause at Voyager 1? Inferences from New Voyager 2 Results

Cummings, A. C. and Stone, E. C. and Richardson, J. D. and Heikkila, B. C. and Lal, N. and Kóta, J. (2021) No Stagnation Region before the Heliopause at Voyager 1? Inferences from New Voyager 2 Results. Astrophysical Journal, 906 (2). Art. No. 126. ISSN 1538-4357. doi:10.3847/1538-4357/abc5c0.

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We present anisotropy results for anomalous cosmic-ray protons in the energy range ~0.5–35 MeV from Cosmic Ray Subsystem (CRS) data collected during calibration roll maneuvers for the magnetometer instrument when Voyager 2 (V2) was in the inner heliosheath. We use a new technique to derive for the first time the radial component of the anisotropy vector from CRS data. We find that the CRS-derived radial solar wind speeds, when converted from the radial components of the anisotropy vectors via the Compton–Getting (C–G) effect, generally agree with those similarly derived speeds from the Low Energy Charged Particle experiment using 28–43 keV data. However, they often differ significantly from the radial solar wind speeds measured directly by the Plasma Science (PLS) instrument. There are both periods when the C–G-derived radial solar wind speeds are significantly higher than those measured by PLS and times when they are significantly lower. The differences are not expected nor explained, but it appears that after a few years in the heliosheath the V2 radial solar wind speeds derived from the C–G method underestimate the true speeds as the spacecraft approaches the heliopause. We discuss the implications of this observation for the stagnation region reported along the Voyager 1 trajectory as it approached the heliopause inferred using the C–G method.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Richardson, J. D.0000-0003-4041-7540
Kóta, J.0000-0002-3715-0358
Additional Information:© 2021. The American Astronomical Society. Received 2020 August 31; revised 2020 October 16; accepted 2020 October 27; published 2021 January 15. A.C.C., E.C.S., N.L., and B.C.H. acknowledge Voyager data analysis support from NASA award number NNN12AA01C. J.D.R. was supported under NASA contract 959203 from the Jet Propulsion Laboratory to the Massachusetts Institute of Technology. A.C.C. and J.D.R. also acknowledge support by NASA grant 18-DRIVE_2-0029, Our Heliospheric Shield, 80NSSC20K0603.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Heliosphere ; Solar wind ; Heliosheath ; Cosmic rays
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Heliosphere (711); Solar wind (1534); Heliosheath (710); Cosmic rays (329)
Record Number:CaltechAUTHORS:20210115-152850922
Persistent URL:
Official Citation:A. C. Cummings et al 2021 ApJ 906 126
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107523
Deposited By: George Porter
Deposited On:19 Jan 2021 16:05
Last Modified:16 Nov 2021 19:04

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