Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

According to standard drift dominated modulation models the intensity variations of galactic cosmic ray protons and electrons respond differently to the latitudinal extension of the heliospheric current sheet α. In an A>0 solar cycle intensities of protons should vary weakly with the latitudinal...

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Bibliographic Details
Published in:Geophysical research letters 1999-07, Vol.26 (14), p.2133-2136
Main Authors: Heber, B., Ferrando, P., Raviart, A., Wibberenz, G., Müller-Mellin, R., Kunow, H., Sierks, H., Bothmer, V., Posner, A., Paizis, C., Potgieter, M. S.
Format: Article
Language:English
Subjects:
Astronomy
Cosmic rays
Earth, ocean, space
Exact sciences and technology
Solar modulation and geophysical effects
Solar system
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Summary:According to standard drift dominated modulation models the intensity variations of galactic cosmic ray protons and electrons respond differently to the latitudinal extension of the heliospheric current sheet α. In an A>0 solar cycle intensities of protons should vary weakly with the latitudinal extension, whereas electrons should show a strong response. We investigate this charge dependent variation in the 1990s (A>0) using Ulysses Kiel Electron Telescope (KET) measurements. Proton measurements at 2.5 GV corrected for latitudinal variations show the same time profile as electrons from mid 1994 until the beginning of 1996, and later from September 1997 to the end of 1997. In 1996 and 1997, when α was below ∼25°, two long lasting time periods were found when electrons had a ∼5–10% higher level. These variations are in agreement with our computations indicating that drift effects play an important role in determining the temporal variation of electrons close to solar minimum.
ISSN:0094-8276
1944-8007
DOI:10.1029/1999GL900482