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Large scale temporal and radial gradients in the IMF: Helios 1, 2, ISEE‐3, and Pioneer 10, 11
Author(s) -
Slavin J. A.,
Smith E. J.,
Thomas B. T.
Publication year - 1984
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/gl011i003p00279
Subject(s) - physics , interplanetary magnetic field , heliosphere , interplanetary spaceflight , solar wind , solar minimum , solar cycle , latitude , interplanetary medium , solar maximum , solar cycle 22 , astronomy , plasma , astrophysics , atmospheric sciences , geophysics , nuclear physics
Recent investigations using measurements at 1 AU have discovered three types of long term variation in the interplanetary magnetic field: solar minimum decreases, solar maximum enhancements, and small decreases around solar reversal. In this study we have examined the 1972‐1982 Helios 1,2, ISEE‐3, and Pioneer 10,11 observations between 0.3 and 12 AU to further investigate these changes. It was found that all three IMF solar cycle effects are also present in the Helios and Pioneer measurements, confirming that these variations occur throughout the low latitude heliosphere. In addition, the comparison of measurements by identical magnetometers on ISEE‐3, Pioneer 10, and Pioneer 11 has revealed a more rapid decrease in IMF intensity than predicted by classical Parker theory. Causes and ramifications of both the long term variations and steeper than expected radial gradients in the interplanetary magnetic field are discussed.