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An ICME observed by Voyager 2 at 58 AU and by Ulysses at 5 AU
Author(s) -
Paularena K. I.,
Wang C.,
von Steiger R.,
Heber B.
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl013122
Subject(s) - physics , ejecta , cosmic ray , astrophysics , proton , astronomy , interplanetary spaceflight , plasma , solar wind , nuclear physics , supernova
Between days 175 and 180 (June 24 through 29) of 1999, the PLS instrument on Voyager 2 observed alpha particle enhancements with fractional percentages of alpha to proton number densities exceeding 10%. Ulysses (located at 5.3 AU) observed at least two candidate source features for these enhancements. To identify the correct source structure, a 1D MHD model was used to propagate the Ulysses plasma data to the Voyager radial position (58.2 AU). An ICME‐related alpha enhancement observed by Ulysses beginning on day 331 (November 27), 1998 appears to be the correct feature. While a speed jump and cosmic ray decreases were observed by Ulysses in conjunction with this alpha enhancement, the timing of these features differed markedly at Voyager 2. The speed jump arrival‐time difference is due to the faster propagation of the shock relative to the rest of the ejecta. It is unclear what mechanism is responsible for the delay in the cosmic ray decrease. Nevertheless, we have demonstrated that alpha enhancement signatures of ICMEs can be used to track these features to heliospheric distances >50 AU.