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Passage of a large interplanetary shock from the inner heliosphere to the heliospheric termination shock and beyond: Its effects on cosmic rays at Voyagers 1 and 2
Author(s) -
Webber W. R.,
Cummings A. C.,
McDonald F. B.,
Stone E. C.,
Heikkila B.,
Lal N.
Publication year - 2007
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 - 10.1029/2007gl031339
Subject(s) - heliosphere , physics , shock (circulatory) , cosmic ray , interplanetary spaceflight , astrophysics , interplanetary medium , solar wind , plasma , nuclear physics , medicine
Using data from the charged particle telescopes on V1 and V2 we have followed the progress of a large interplanetary shock as it passes V2 at a distance of 79 AU at about 2006.16, then later crosses the heliospheric termination shock finally reaching V1 at a distance ∼100 AU. A decrease ∼15% is observed in the V2 >70 MeV rate starting at 2006.19 and three smaller decreases starting at 2006.29, 2006.50 and 2006.86 are observed at V1. From the timing of the first two decreases at V1 we are able to determine that the average shock speed slows down at the termination shock from ∼600 km s −1 to 210–270 km s −1 . Decreases of ∼30–50% in anomalous He and galactic H are observed at V2 when the shock passes this location inside the termination shock. Smaller decreases are observed for both of these components when the weakened interplanetary shock passes V1 at 2006.50. These results define the extent and magnitude of solar modulation effects on cosmic rays caused by transients both inside and beyond the termination shock.