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Transient intensity changes of cosmic rays beyond the heliospheric termination shock as observed at Voyager 1

Webber, W. R. and Cummings, A. C. and McDonald, F. B. and Stone, E. C. and Heikkila, B. and Lal, N. (2009) Transient intensity changes of cosmic rays beyond the heliospheric termination shock as observed at Voyager 1. Journal of Geophysical Research A, 114 (7). A07108. ISSN 0148-0227. doi:10.1029/2009JA014156.

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This paper continues our studies of temporal variations of cosmic rays beyond the heliospheric termination shock (HTS) using Voyager 1 (V1) data when V1 was beyond 94 AU. This new study utilizes cosmic ray protons and electrons of several energies. Notable transient decreases of 5–50% are observed in galactic cosmic ray nuclei and electrons at V1 shortly after similar decreases are observed at Voyager 2 (V2) still inside the HTS. These decreases at V1 appear to be related to the large solar events in September 2005 and December 2006 and the resulting outward moving interplanetary shock. These two large interplanetary shocks were the largest observed at V2 after V1 crossed the HTS at the end of 2004. They were observed at V2 just inside the HTS at 2006.16 and 2007.43 providing timing markers for V1. From the timing of the intensity decreases observed at V1 as the shocks first reach the HTS and then later reach V1 itself, we can estimate the shock speed beyond the HTS to be between 240 and 300 km s^(−1) in both cases. From the timing of the decreases observed when the shock first reaches the HTS and then several months later encounters the heliopause, we can estimate the heliosheath thickness to be 31 ± 4 and 37 ± 6 AU, respectively, for the two sequences of three decreases seen at V1. These values, along with the distances to the HTS that are determined, give distances from the Sun to the heliopause of 121 ± 4 and 124 ± 6 AU, respectively.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:©2009. American Geophysical Union. Received 9 February 2009; accepted 28 May 2009; published 30 July 2009. This work is supported at NMSU by subcontract 1257395 from JPL. W.R.W. appreciates discussions with coauthors A.C.C. and F.B.M. Zuyin Pu thanks the reviewers for their assistance in evaluating this paper.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:cosmic rays
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2009-32
Issue or Number:7
Record Number:CaltechAUTHORS:20090817-144816744
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Official Citation:Webber, W. R., A. C. Cummings, F. B. McDonald, E. C. Stone, B. Heikkila, and N. Lal (2009), Transient intensity changes of cosmic rays beyond the heliospheric termination shock as observed at Voyager 1, J. Geophys. Res., 114, A07108, doi:10.1029/2009JA014156.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15110
Deposited By: George Porter
Deposited On:02 Sep 2009 21:31
Last Modified:08 Nov 2021 23:16

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